An Overview of the ACE-2 Clear Sky Column Closure Experiment
(CLEARCOLUMN)

PHILIP B. RUSSELL^1\*^ and JOST HEINTZENBERG^2^

^1^NASA Ames Research Center, Moffett Field, CA 94035-1000 USA

^2^Institute for Tropospheric Research (IFT), 04318 Leipzig, Germany

##### Submitted to *Tellus B* (Special Issue on ACE-2), January 1999

Revised 29 August 1999

Final revision 14 October 1999

\*Corresponding author

Philip B. Russell, MS 245-5, NASA Ames Research Center, Moffett Field,
CA 94035-1000 USA

E-mail: <prussell@mail.arc.nasa.gov>.

Phone: 1-650-604-5404. Fax: 1-650-604-6779

Computer: Macintosh. Word processor: Word 98 for Macintosh

An Overview of the ACE-2 Clear Sky Column Closure Experiment
(CLEARCOLUMN)

PHILIP B. RUSSELL1 and JOST HEINTZENBERG2

1NASA Ames Research Center, Moffett Field, CA 94035-1000 USA

2Institute for Tropospheric Research (IFT), 04318 Leipzig, Germany

ABSTRACT

As one of six focused ACE-2 activities a clear sky column closure
experiment (CLEARCOLUMN) took place in June/July 1997 at the southwest
corner of Portugal, in the Canary Islands, and over the eastern Atlantic
Ocean surrounding and linking those sites. Overdetermined sets of
volumetric, vertical profile and columnar aerosol data were taken from
the sea surface to \~5 km asl by samplers and sensors at land sites
(20-3570 m asl), on a ship, and on four aircraft. In addition, five
satellites measured upwelling radiances used to derive properties of the
aerosol column. Measurements were made in a wide range of conditions and
locations (e.g., the marine boundary layer with and without continental
pollution, the free troposphere with and without African dust). Numerous
tests of local and column closure, using unidisciplinary and
multidisciplinary approaches, were conducted. This paper summarizes the
methodological approach, the experiment sites and platforms, the types
of measurements made on each, the types of analyses conducted, and
selected key results, as a guide to the more complete results presented
in other papers in this special issue and elsewhere. Example results
include determinations of aerosol single scattering albedo by several
techniques, measurements of hygroscopic effects on particle light
scattering and size, and a wide range in the degree of agreement found
in closure tests. In general, the smallest discrepancies were found in
comparisons among (1) different techniques to measure an optical
property of the ambient, unperturbed aerosol (e.g., optical depth,
extinction, or backscatter by sunphotometer, lidar, and/or satellite) or
(2) different techniques to measure an aerosol that had passed through a
common sampling process (e.g., nephelometer and size spectrometer
measurements with the same or similar inlets, humidities and
temperatures). Typically, larger discrepancies were found between
techniques that measure the ambient, unperturbed aerosol and those that
must reconstruct the ambient aerosol by accounting for (a) processes
that occur during sampling (e.g., aerodynamic selection, evaporation of
water and other volatile material) or (b) calibrations that depend on
aerosol characteristics (e.g., size-dependent density or refractive
index). A primary reason for the discrepancies in such cases is the lack
of validated hygroscopic growth models covering the necessary range of
particle sizes and compositions. Other common reasons include (1) using
analysis or retrieval techniques that assume aerosol properties (e.g.,
density, single scattering albedo, shape) that do not apply in all cases
and (2) using surface measurements to estimate column properties. Taken
together, the ACE-2 CLEARCOLUMN data set provides a large collection of
new information on the properties of the aerosol over the northeast
Atlantic Ocean. CLEARCOLUMN studies have also pointed to improved
techniques for analyzing current and future data sets (including
satellite data sets) which will provide a more accurate and
comprehensive description of the Atlantic-European-African aerosol. Thus
they set the stage for an improved regional quantification of radiative
forcing by anthropogenic aerosols.

**1. Introduction**

The Clear Sky Column Closure Experiment (CLEARCOLUMN) is one of six
focused activities conducted as part of the Second Aerosol
Characterization Experiment (Raes et al., 2000; Verver et al., 2000).
The purpose of CLEARCOLUMN is to evaluate the uncertainty in methods
used to assess the direct radiative forcing of aerosols over the North
Atlantic. The approach is to use over-determined sets of aerosol optical
properties measured in columns and profiles and connected through
radiation models. In each column, the experiment measured or derived the
aerosol parameters needed to quantify the direct radiative forcing of
the tropospheric aerosol. The satellites involved in this study can then
be used to relate the direct radiative forcing derived in CLEARCOLUMN
and in other columnar experiments to the larger North Atlantic region
(e.g., Bergstrom and Russell, 1999). CLEARCOLUMN addresses the third
ACE-2 scientific question (Raes et al., 2000):

*Can the measured physical and chemical properties of the aerosol in the
vertical column be used to accurately predict the integrated direct
effect of aerosols on radiative transfer?*

CLEARCOLUMN used a three-pronged closure approach to address this
question:

1\. From extinction, scattering, and physico-chemical aerosol
measurements at several ground elevations, on the ship, on airborne
platforms, and in lidar beam profiles, unidisciplinary and
multidisciplinary [local closure]{.underline} can be tested at different
altitudes in the boundary layer and free troposphere.

2\. Vertical integrals of the profile information can be compared to
columnar extinction data derived from surface-based and air- and
space-borne radiometers (supported by data on water-leaving radiances
from ship- and airborne platforms) in order to test [column
closure]{.underline} of aerosol optical properties.

3\. Radiative fluxes from measurements can be compared to corresponding
results derived by means of radiative transfer modeling from the aerosol
and trace-gas measurements.

**2. Methodological Approach**

CLEARCOLUMN took place in June/July, 1997, near Sagres, Portugal, in the
Canary Islands, and over the eastern Atlantic Ocean surrounding and
linking those sites. Fig. 1 shows a schematic overview of sites and
platforms, and Table 1 lists coordinates of the land sites used in
CLEARCOLUMN. Table 2 lists measurements made at or on each CLEARCOLUMN
platform.

The central site near Sagres was S-50 (Table 2a) where the most powerful
lidar was stationed together with sun and sky radiometry, stellar
radiometry, boundary layer meteorology and a radiosonde. The lidar
scanned in elevation angle, from near horizontal over the ocean west of
Sagres, through the vertical, and towards the slopes of Mt. Fóia (900m
asl) where radiometric, meteorological and aerosol characterisation
instrumentation was set up at two altitudes (900 and 500 m asl).

The mountain top site near Sagres (S-900, Table 2c) was most
representative for the upper part of the regional boundary layer and
free troposphere aerosol. Thus S-900 was the second Sagres site with an
intensive aerosol characterisation. A ship (R/V Vodyanitskiy, Table 2d)
on suitable trajectories leading to or from the Sagres area was equipped
with another lidar, a tracking sunphotometer, and a suite of aerosol
characterisation instruments. The boundary layer aerosol optical
measurements at the Sagres surface sites were connected through flight
missions by a C-414 aircraft (cf. Table 2j) carrying a spectral
radiometer. Within and above the boundary layer, two research aircraft
(MRF C-130 and the French ARAT, Tables 2k and 2l) flew vertical profiles
and horizontal transects over the Sagres area to connect the sites and
to extend the aerosol characterisation well into the free troposphere.

On the island of Tenerife in the Canaries, the Punta del Hidalgo
lighthouse site (Table 2e) and the Izaña mountain ridge observatory
(Table 2g) had extensive suites of instrumentation to characterize
aerosol chemical, physical, and optical properties in the marine
boundary layer and free troposphere, respectively. Included were sun/sky
radiometers at both sites and an elevation-scanning MicroPulse Lidar
(MPL) at Izaña. Two additional sites near sea level, Santa Cruz de
Tenerife and Las Galletas (Table 2f), operated radiometers; Las Galletas
also had a scanning MPL. Sun and sky radiometers were also operated at
San Cristobal de La Laguna (Table 2f). The site near the summit of Teide
(Table 2h) operated shadow-band and sun/sky radiometers.

The Pelican aircraft (Table 2i) measured aerosol chemical, physical, and
optical properties, plus radiative fluxes and meteorological parameters,
from sea level to \~4 km asl. Radiances measured by sensors on five
satellites (ADEOS, ERS-2, NOAA-12, NOAA-14, METEOSAT; Fig. 1 and Table
2m) were used to derive aerosol and other properties.

*2.1. Methodology for evaluation*

For the evaluation of the field data a clearly-defined evaluation scheme
was formulated that reached beyond the presentation of quality
controlled data to a central ACE-2 data base and beyond the goals of
CLEARCOLUMN proper towards the overall objectives of ACE-2 aiming at the
regional quantification of radiative forcing in the polluted marine
atmosphere. Fig. 2 shows a flow chart of this methodology.

After primary quality control and derivation of physical quantities from
the individual measured parameters the results were segregated into air
mass and aerosol types. A variety of closure tests (Quinn et al., 1996)
were then conducted, yielding multiparameter evaluations of the degree
of consistency or inconsistency between experimental and modeling
approaches. A number of \"Golden Days\" were defined, on which to focus
the initial data evaluation. For Sagres data, these days are listed in
Table 3. Two time periods were selected for detailed analyses:
1997-06-20 ±2 days as clean marine reference days and 1997-07-20 ±2 days
as the period with highest continental aerosol burden. Golden days for
the Tenerife area were 21 June and 8, 10, and 17 July. For the ship they
were 24, 27, and 30 June and 6, 10, and 22 July. 10 July included
measurements by the Pelican near the ship to the northeast of the Canary
Islands.

**3. Results**

*3.1. Surface-based volumetric data*

Complete aerosol size distributions have been derived at Sagres 50 (
Neusüß et al., 2000) and submicrometer size distributions at Mt. Fóia
(Sagres-900) (Henning et al., 1998). Grand average distributions for
clean marine and polluted periods clearly show that pollution aerosols
were observed at both sites and that the coastal site always was under
marine influence with a significant coarse particle component.
Simultaneous co-located measurements of aerosol light scattering,
hemispheric backscattering, and chemical composition permitted tests of
closure with the size distribution measurements. Also on the research
vessel concurrent physical, chemical and optical data were collected for
optical closure tests (Bates et al., 2000; Quinn et al., 2000).
Trajectory analyses show that both continental and marine flows were
sampled by the ship, and different trajectories produced systematic
differences in a variety of chemical and optical properties (see below).

Hygroscopic growth properties of the aerosol are crucial parameters
which are required to connect volumetric aerosol data measured at
reduced relative humidity to optical aerosol properties derived at
ambient relative humidities. Thus the ACE-2 program included such growth
measurements at the land-based sites (Swietlicki et al., 2000; Carrico
et al., 2000), onboard the research vessel (Livingston et al., 2000;
Quinn et al., 2000), and on the Pelican aircraft (Gassó et al., 2000).

For the interpretation of both chemical and optical data the
carbonaceous aerosol component (both organic and inorganic) is of
particular importance. Measurements of aerosol light absorption are also
critical, both for direct use in determining aerosol optical properties
such as single scattering albedo, and for estimation of equivalent black
carbon amounts using empirical conversion factors. Consequently, most of
the CLEARCOLUMN platforms and sites and also long term ACE-2 aerosol
measurements included measurements of aerosol carbon and/or light
absorption, concurrent with other chemical, physical, and optical
measurements (Quinn et al., 2000; Novakov et al., 2000; Neusüß et al.,
2000; Putaud et al., 2000) .

For Sagres-50 data Neusüß et al. (2000) report a three-way comparison of
size-resolved mass concentrations derived from (1) gravimetric analysis
of impactor samples (collected and analyzed at 60% RH), (2) chemical
analysis of the impactor samples, and (3) number-size distributions
measured concurrently by Twin Differential Mobility Analyser (TDMPS) and
Aerodynamic Particle Counter (APS) (both at RH\<10%). Chemical results
are reported for Cl^-^, NO~3~^-^, SO~4~^2-^, NH^4+^, Na^+^, Mg^2+^,
K^+^, Ca^2+^, volatile and nonvolatile carbon, and water. For
submicrometer particles, water uptake was calculated using hygroscopic
growth factors measured for size-segregated particles in the diameter
range 35-250 nm; for supermicrometer particles seasalt growth factors
from Tang et al. (1997) were used. Overall, Neusüß et al. find that
masses derived by each method agree within the combined uncertainties,
which they estimate to be about ±20% for each method when masses are
integrated over geometric diameters D~p~\<3 μm. Results are expressed as
slopes of linear regression fits obtained when comparing pairs of
methods for 15 cases ranging from clean to polluted (total masses 5 to
40 μg m^-3^). For example, they find that, on average, masses for
D~p~\<3 μm derived from TDMPS/APS number-size distributions were 23%
larger than corresponding masses determined gravimetrically from
impactor samples. Analogously, chemical masses for D~p~\<3 μm were on
average 2% larger than the corresponding gravimetric masses. Results are
also given for size classes corresponding to four or five impactor
stages. Relative mass differences and uncertainties were found to depend
on size class, but were independent of the degree of pollution.

Also for Sagres-50 data Philippin et al. (1998; personal communication)
performed tests of local optical closure for the dry submicrometer
aerosol by comparing measured scattering and backscattering coefficients
at wavelength 550 nm with values calculated from measured size
distributions and chemical compositions. For scattering coefficients
they found best agreement when they modeled the aerosol as an internal
mixture of sulfate and nonvolatile carbon with size-resolved mass
fractions from three impactor stages.

From samples taken aboard R/V Vodyanitskiy (Table 2d) at 10 m asl,
Novakov et al. (2000) found concentrations of aerosol organic carbon
(OC) that averaged 0.89 μg m^-3^ for submicrometer aerosols during
polluted conditions. This average is similar to the averages for OC
measured at Sagres (0.61 μg m^-3^) and Punta del Hidalgo (0.64 μg m^-3^)
during polluted conditions (Putaud et al., 2000). By combining measured
submicron nonseasalt sulfate (nss SO~4~^2-^) and black carbon (BC),
Novakov et al. (2000) found nss SO~4~^2-^/BC ratios that averaged 12
over the ACE-2 Vodyanitskiy cruise, very similar to the average
SO~4~^2-^/BC ratio of 11 measured off the eastern US coast in aircraft
samples at altitudes between 100 and 3000 m asl during TARFOX (Novakov
et al., 1997; Hegg et al., 1997). (The distinction between nss SO~4~^2-^
and total SO~4~^2-^ was unimportant for the TARFOX samples, because the
TARFOX inorganic analysis yielded sulfate as the only anion present
above trace levels, and mass budget closure was obtained within 10% by
using only sulfate and carbonaceous measurements compared to total
masses from filters.)

In contrast, ratios of sulfate to total carbon (TC) differed
significantly between ACE-2 Vodyanitskiy samples and TARFOX samples.
Vodyanitskiy nss SO~4~^2-^/TC ratios averaged 5.3±2.9 for submicron
aerosol samples and 2.9±1.3 for submicron plus supermicron samples.
TARFOX SO~4~^2-^/TC ratios were negatively correlated with altitude,
averaging 1.6±0.7 at the lowest sampling altitudes (100- 300 m asl), 1.2
over all TARFOX filter sampling altitudes (100-3000 m), and 0.6±0.6
above 2500 m. Since the TARFOX aerosol intake system collected particles
with D~p~\<\~5 μm, it is most appropriate to compare the Vodyanitskiy
submicron plus supermicron SO~4~^2-^/TC ratio of 2.9±1.3 to the TARFOX
ratio of 1.6±0.7 at 100-300 m. Even with this selected comparison, the
TARFOX SO~4~^2--^/TC ratio is significantly less than the Vodyanitskiy
ratio, indicating larger aerosol organic carbon fractions in TARFOX than
in the Vodyanitskiy samples. It is interesting to note that at Izaña
(2360 m asl, Table 2g), Putaud et al. (2000) measured submicron nss
SO~4~^2-^/TC of 0.71 in background conditions and 0.36 in flows from
North America. These values suggest that both increasing altitude and a
North American origin tend to reduce nss SO~4~^2-^/TC, reflecting larger
aerosol organic carbon fractions.

By combining shipboard measurements of aerosol light scattering and
absorption (for D~aero~\<10 μm, at RH 55% and wavelength 550 nm), Quinn
et al. (2000) obtained single scattering albedo values that had mean and
standard deviation 0.95±0.03 in continental flows (range 0.81 to 0.99)
and 0.98±0.01 in marine flows (range 0.93 to 0.99). Their technique for
measuring absorption, which used a Particle Soot Absorption Photometer,
included an empirically-derived correction factor to account for the
small (1 to 1.5%) positive artifact caused by instrumental
interpretation of scattering as absorption. Quinn et al. (2000) also
report a significant relationship between air mass origin and the
wavelength dependence of aerosol light scattering, σ~sp~(λ).
Specifically, the Ångström exponent (a ≡ -dlnσ~sp~(λ)/dlnλ) between 550
and 700 nm for D~aero~\<10 μm at 55% RH was 1.2±0.3 in continental flows
and 0.24±0.26 in marine flows. This reflects the increased importance of
scattering by submicrometer aerosols in continental flows. At Sagres-50
for RH 27% and D~aero~\<10 μm, Carrico et al. (2000) found Ångström
exponents of 1.48±0.26 and 0.57±0.34 during pollution outbreaks and
"clean" periods, respectively.

Carrico et al. (2000) combined nephelometer measurements of aerosol
light scattering and aethalometer derived light absorption estimates for
particles with D~aero~\<10 μm (RH \< 30%) to obtain single scattering
albedos ω(550 nm). Their best estimate of ω(550 nm) at RH 27% during
pollution outbreaks at Sagres-50 is 0.94 with an uncertainty of 0.02.
During "clean" periods the corresponding best estimate was 0.93 with the
same uncertainty. Their measured effects of aerosol hygroscopic growth
on light scattering increased ω(550 nm) by about 0.01, assuming light
absorption is independent of RH. Given uncertainties in the aethalometer
measurement (Heintzenberg et al., 1997) and the range of air masses and
RH at Sagres-50, they estimate the range of ω(550 nm) there as 0.91 to
0.97.

*3.2. Profile and column data*

At Sagres 50 and onboard the research vessel multiwavelength lidar
profiles were taken throughout the ACE-2 experiment, spanning conditions
from clean marine aerosol in a shallow boundary layer through European
pollution filling most of the first 3 km altitude range. From the
Sagres-50 profiles height-dependent in-situ aerosol size distributions
were inverted (Wagner et al., 1998). The lidar profiles also yielded
boundary layer heights and limits of elevated aerosol layers which
compared very well with concurrent local radiosonde temperature
profiles.

Welton et al. (2000) present micropulse lidar measurements of upslope
aerosols and African dust layers over Izaña on Tenerife (Table 2g). They
use an iterative algorithm that incorporates simultaneous sunphotometer
optical depth measurements to derive height-independent
backscatter-to-extinction ratios at the single lidar wavelength (523 nm)
and thereby obtain vertical profiles of aerosol extinction and optical
depth. Comparisons between an independent optical depth measurement on
the Teide summit (3570 m asl, Table 2h, Formenti et al., 2000) and the
lidar value at that altitude yielded agreement to within 0.01, in both
upslope and dust-layer conditions (optical depth range 0.003 to 0.075).
Comparison to an airborne sunphotometer profile (Schmid et al., 2000)
within the dust layer yielded differences of ±0.02 or less at all
altitudes (\~2500-3800 m asl), over which optical depth decreased from
0.22 to 0.05.

Powell et al. (2000) report measurements of marine boundary layer and
desert dust aerosols made with the micropulse lidar at Las Galletas on
the southern tip of Tenerife (Table 2f). They used the slant-sensing
technique of measuring profiles at several zenith angles, which,
together with an assumption of horizontal and temporal homogeneity
during the scanning period, yields layer optical depths and
backscatter-to-extinction ratios. This information was then employed
when the lidar was vertically pointing to obtain the temporal evolution
of backscatter, extinction, and optical depth profiles. The attenuation
of horizontal lidar profiles was also used to determine the extinction
coefficient at the lidar altitude. Comparisons to airborne sunphotometer
measurements of layer optical depth (Schmid et al., 2000) produced
differences of ±0.01 for dust and boundary-layer aerosol optical depths
(which were 0.24 and 0.05, respectively, at the lidar wavelength of 530
nm).

Flamant et al. (2000) report airborne lidar measurements and closure
studies for a European pollution outbreak sampled by the ARAT aircraft
(Table 2l). The lidar mapped vertical profiles of the pollution plume
and the marine boundary layer aerosol as the plume was carried from the
coast of Portugal near Sagres over the ship and beyond over the Atlantic
Ocean. Particle extinction profiles were derived from the lidar data
using an extinction coefficient at a reference height and parameterized
model profiles of backscatter-to-extinction ratio (BER). The reference
extinction was obtained using free-tropospheric nephelometer
measurements on the ARAT; model BER profiles were obtained using size
distribution spectra measured on the ship and on the ARAT. Lidar-derived
extinction profiles at 0.55 μm differed from nephelometer-measured
scattering profiles by \~0.03 km^--1^ or less. Values of aerosol optical
depth (AOD) derived from the lidar ranged from 0.055 to 0.10. When
compared to ship sunphotometer measurements, differences were 0.02 or
less, within the combined lidar and sunphotometer uncertainties. In
contrast, AODs derived from METEOSAT radiances exceeded the lidar values
by 0.01 to 0.08, with the largest differences in the area where the
pollution plume contributed most to column optical depth. Flamant et al.
suggest that the difference may be caused by large uncertainties
associated with the Meteosat sensitivity for small AODs or by the
presence of thin scattered clouds.

At all Sagres sites multiwavelength sun and sky photometry yielded
aerosol optical thickness spectra, sky brightness distributions and
phase functions (Bugalho et al., 1998; Vitale et al., 2000; von
Hoyningen-Huene, 1998). The Sagres photometer measurements were also
used to derive columnar amounts of precipitable water (Tomasi et al.,
2000). At Sagres-50 a star photometer for the first time provided night
time aerosol optical thickness spectra which were complementary and
consistent with the daytime data yielding diurnal in situ aerosol
optical variations over the whole experiment (von Hoyningen-Huene et
al., 1998; personal communication). These data show, for example, that
wind shifts associated with the diurnal cycle in land-sea air exchange
were accompanied by systematic changes in both aerosol optical thickness
and its wavelength dependence. In particular, when wind shifted from WNW
to ENE during evening and night hours, the aerosol optical thickness δ
at wavelength 1 μm decreased and the wavelength exponent (α ≡
-dln δ(λ)/dlnλ) increased.

von Hoyningen-Huene et al. (1998; personal communication) also combined
measurements of optical depth wavelength dependence, sky brightness
angular dependence, and radiative fluxes at Sagres-900 (Table 2c) to
obtain best-fit values for the single scattering albedo ω of the ambient
(hydrated) column aerosol, averaged over all solar wavelengths. In this
way they obtained ω = 0.98±0.03 for maritime-influenced conditions (8
cases) and 0.90±0.04 for polluted continental conditions (6 cases). (All
cases were without African dust.) They also found that, for
maritime-influenced cases at both Sagres-50 and Sagres-900, the aerosol
phase functions they derived from sky brightness measurements could be
fitted better with a scattering theory for non-spherical particles than
with the Mie theory for homogeneous spheres. Measured scattering phase
functions for maritime-influenced cases with low relative humidity
(RH\<78%) differed more from Mie phase functions than did measured
maritime-influenced phase functions for high-humidity periods (RH\>78%).
They attributed these results to asphericity of seasalt particles,
especially in low-humidity conditions. In continental air masses
Mie-theory phase functions fitted the measured phase functions well.

Tenerife sun and sky photometer measurements from within the boundary
layer and in the free troposphere are reported by Smirnov et al. (1998),
Formenti et al. (2000), and Elias et al. (2000). They provide results
for optical depth, wavelength dependence, and column aerosol phase
functions, documenting the systematic changes that occurred on the
several occasions when African dust was carried over Tenerife (e.g.,
increasing optical depth, decreasing wavelength dependence, decreased
polarized phase function at 60° scattering angle).

Shipboard sunphotometer measurements of aerosol optical depth (AOD)
spectra and column water vapor (CWV) are reported by Livingston et al.
(2000). Comparisons between CWV measured by sunphotometer and by
radiosonde yielded good agreement, with an rms difference of 0.09 g
cm^-2^ in 7 samples having a CWV range of 1.6 to 3.2 g cm^-2^. AODs
inferred from shipboard aerosol lidar backscatter measurements during
one day were consistent with those measured by the shipboard
sunphotometer, but the uncertainties associated with deriving optical
depth from the shipboard lidar data were large (\~factor 2) because of
the need to assume an extinction-to-backscatter ratio that differed for
maritime and continental-influenced aerosols. Livingston et al. (2000)
also performed column closure tests between AODs measured by
sunphotometer and computed by combining shipboard particle size
distribution measurements with models of hygroscopic growth and
radiosonde humidity profiles (using the assumption that dry particle
size distribution and composition were independent of height in the
boundary layer). These closure tests often produced big discrepancies,
in large part because of their great sensitivity to models of
hygroscopic growth, which vary considerably and have not been validated
over the necessary range of particle size/composition distributions. The
wavelength dependence of shipboard sunphotometer AODs was compared with
the corresponding dependence of aerosol extinction calculated from
shipboard measurements of aerosol size distribution and of total
scattering measured by a shipboard integrating nephelometer. Results of
these comparisons were highly variable, illustrating again the great
difficulty of deriving column values from point measurements.

Profile data from the Pelican aircraft (Table 2i) have been used in a
variety of ways to study both boundary-layer and free-tropospheric
aerosols. For example, Collins et al. (2000) combine vertical profiles
of Pelican-measured particle number-versus-size spectra with
size-resolved chemical compositions to derive scattering, hemispheric
backscattering, and extinction coefficient profiles and compare them to
the measurements of Öström and Noone (2000), Gassó et al., (2000) and
Schmid et al. (2000). The size-resolved chemical compositions used in
each case are based on boundary-layer and free-tropospheric measurements
made at Punta del Hidalgo and Izaña (Tables 2e, 2g; Putaud et al., 2000)
and are also consistent with the size-integrated compositions measured
on the Pelican aircraft and reported by Schmeling et al. (2000). Collins
et al. use the hygroscopic properties of the aerosol constituents to
derive size-resolved particle densities and refractive indices and
thereby account for the sampling processes that affect each particle
prior to detection (e.g., inlet aerodynamic size selection, evaporation
by ram-air and sheath-air heating) as well as the size calibration of
optical particle counters. This permits reconstructing the ambient
aerosol that existed before its distortion by sampling processes (as is
needed for comparison to, e.g., sunphotometer measurements---see below),
as well as the aerosol within dried and humidified nephelometers at
specified humidities (e.g., Gassó et al., 2000; Öström and Noone, 2000).

Schmeling et al., (2000) report aerosol chemical composition
measurements from samples collected aboard the Pelican. They derive
spectra of ambient aerosol refractive index for each sample by combining
their aerosol species results with the Howell and Huebert (1998)
parameterization for water vapor uptake and with published species
refractive index spectra. They note, however, that their imaginary
refractive index results are subject to underestimation, because
sampling constraints resulted in detection limits for elemental carbon
that were between 1% and 3% of total sample mass, and in fact all
samples had carbon below the detection limit.

Gassó et al. (2000) report measurements of hygroscopic effects on
aerosol light scattering measured by a passive humidigraph on the
Pelican. The passive humidigraph uses two nephelometers, one designed to
operate below ambient RH, and the other above. Particle scattering
coefficients σ~sp~ at wavelength 530 nm from the two nephelometers are
used to solve for the exponent γ in the equation

> σ~sp~(RH) = k(1-RH\[%\]/100%)^--γ^. (1)

The value of γ is then used to estimate σ~sp~ at the ambient RH, and
also to estimate σ~sp~(80%)/σ~sp~(30%) (=\[0.7/0.2\]^γ^). Gassó et al.
note that since Eq. (1) does not account for deliquescence and
hysteresis effects, their approach is more applicable to aerosols where
these effects are expected to be small, or to dust aerosols, where
hygroscopicity is itself expected to be small. They present results for
a vertical profile of γ, obtained on a case when Pelican descended
through an African dust layer at 3800-2600 m ASL and into the polluted
marine boundary layer (1000-50 m asl); values of γ in the dust and
polluted marine layers were \~0.15 and 0.55, respectively. Over all
ACE-2 Pelican flights they obtained γ values that had mean and standard
deviation 0.23±0.05 for dust (7 samples), 0.57±0.06 for polluted marine
aerosols (37 samples), and 0.69±0.06 for clean marine aerosols (21
samples). Corresponding values of σ~sp~(80%)/σ~sp~(30%) are 1.33±0.07,
2.04±0.16, and 2.37±0.19. These results are in qualitative agreement
with previous results reported by Hegg et al. (1996), Covert et al.
(1972), Fitzgerald et al. (1982), and Kotchenruther et al. (1999).
However, they significantly exceed the results obtained at Sagres-50 by
Carrico et al. (2000), who performed increasing and decreasing
controlled RH scans with two nephelometers in series.

Schmid et al. (2000) compare airborne sunphotometer-measured optical
depth profiles to vertical integrals of the Collins et al. results.
Their sunphotometer optical depth profiles are also differentiated
vertically to yield extinction profiles, which are compared to the
profiles mentioned above. For the two cases in which an elevated African
dust layer was sampled, AOD values from sunphotometer and in situ size
distributions agreed to within 7.5% for wavelengths λ = 380 to 1060 nm.
However, at λ = 1558 nm, values from in situ size distributions exceeded
sunphotometer values by \~20%. Schmid et al. note that the difference
might be caused by an incorrect assumed refractive index at 1558 nm, but
that refractive index measurements covering the full 380-1558 nm range
are lacking. In the marine boundary layer both Schmid et al. and Collins
et al. note a tendency for extinction and optical depth values from in
situ size distributions to be somewhat less than sunphotometer values
(e.g., by 10%, 25%, and 15%, and on July 8, 10, and 17, respectively).
Although they both note that these differences are within the combined
uncertainties, Schmid et al. point out that the sign of the difference
(in situ \< sunphotometer) is the same as in several previous studies,
and they suggest possible reasons for this commonality (see "Summary and
conclusions", below).

Schmid et al. also compare their sunphotometer optical depths and
extinctions to those obtained from the nephelometer and absorption
photometer measurements of Gassó et al. (2000) and öström and Noone
(2000) on the same aircraft. Optical depth differences ∆AOD ranged from
+15% to --44%, significantly exceeding ∆AOD in the size
distribution/sunphotometer comparisons. Schmid et al. attribute the
larger differences to the fact that the nephelometer and absorption
photometer sampled the aerosol through a cyclone with aerodynamic cutoff
diameter 2.5 μm, whereas the size distribution measurements did not.
Although inlet cyclone correction factors were applied to the
nephelometer and absorption photometer values, the factors were
relatively large (e.g., 1.17-1.47 in the MBL and 2.8-3.2 in the dust),
and their uncertainties could have accounted for the AOD differences
obtained.

Schmid et al. also report comparisons between size distributions
measured in situ and retrieved from the wavelength dependence of
sunphotometer optical depths and extinctions. They note that agreement
was better in the MBL than in the elevated dust layer, with differences
in the dust layer possibly attributable to the lack of refractive index
information covering the full 380-1558 nm range noted above.

The Pelican measurements also demonstrated for the first time agreement
between vertical profiles of column water vapor (CWV) derived from
sunphotometer-measured transmission and obtained by integrating profiles
from radiosonde and airborne hygrometer. The agreement was typically
within ±0.15 g cm^--2^ in profiles from the surface to 3.8 km with CWV
values ranging from 0.2 to 1.7 g cm^--2^. The airborne sunphotometer CWV
profiles were also differentiated vertically to yield profiles of water
vapor density, producing values that agreed typically to within ±1 g
cm^--3^ with radiosonde and airborne hygrometer values that ranged from
0.1 to 17 g cm^--3^ (Schmid et al., 2000; Livingston et al., 2000).

Values of aerosol single scattering albedo ω determined from scattering
and absorption measurements made aboard Pelican (Öström and Noone, 2000)
varied considerably. Flight-leg means and standard deviations in the
boundary layer at altitudes 980 to 30 m ranged from 0.75±0.43 to
0.96±0.19 for the dry aerosol; corresponding upper limits for the
ambient aerosol at 90% RH ranged from 0.89 to 0.99. Flight-leg means
within African dust layers at altitudes 3250 to 3885 m varied from
0.73±0.12 to 0.91±0.11 (Öström and Noone, 2000).

*3.3. Satellite studies and comparisons*

(Durkee et al., 2000) present a regional view of ACE-2 aerosol
properties derived from Advanced Very High Resolution Radiometer (AVHRR)
radiance measurements on the NOAA--14 satellite and compare results to
those obtained in ACE-1 and TARFOX. They also compare AVHRR optical
depths at 630 and 860 nm with values measured in ACE-2 by a variety of
sunphotometers on land, ship, and the Pelican aircraft (e.g., Schmid et
al., 2000; Livingston et al., 2000). For the 23 cases that met
coincidence criteria (described in detail by Durkee et al.), the
correlation coefficient between AVHRR and sunphotometer optical depths
was 0.93 for 630 nm wavelength and 0.92 for 860 nm wavelength. The
standard error of estimate was 0.025 for 630 nm wavelength and 0.023 for
860 nm wavelength. Included in the comparison were three cases where
African dust was present. In these cases, AVHRR optical depths
systematically underestimated sunphotometer optical depths, by amounts
ranging from 0.01 to 0.08 (with optical depths ranging from \~0.3 to
0.4). As Durkee et al. note, agreement for the dust cases would be
improved by changing the nonabsorbing aerosol optical model used in the
AVHRR retrievals to an absorbing one; dust aerosol shape effects on the
scattering phase function should also be considered (e.g., Mishchenko et
al., 1997). Because there were only 3 cases of African dust in the
intercomparison, they had little effect on the overall correlation and
rms difference reported above.

Using the AVHRR optical depths, Durkee et al. point out some interesting
features of the spatial patterns and frequency distributions of ACE-2
aerosol optical depths in comparison to those from ACE-1 and TARFOX. For
example, they note the rather wide range of ACE-2 aerosol optical
depths, from very clean to polluted. This produced, for example, an
ACE-2 mode optical depth at 630 nm of 0.095, actually less than the
ACE-1 mode of 0.115. The ACE-2 mean aerosol optical depth was 0.162,
falling between the ACE-1 and TARFOX values of 0.130 and 0.353,
respectively. And the ACE-2 standard deviation was 0.109, larger than
the ACE-2 mode (reflecting the broad, skewed ACE-2 distribution) and
nearly 4 times the ACE-1 standard deviation. Values quoted in this
paragraph are for wavelength 630 nm; similar contrasts with ACE-1 and
TARFOX were observed at 860 nm.

von Hoyningen-Huene et al. (1999; personal communication) present
results of a study comparing ground-based aerosol optical thickness
(AOT) measurements at Sagres-50, Sagres-500 (Monchique), and Sagres-900
(Mt. Foia) with retrievals from the Ocean Color and Temperature Sensor
(OCTS) on the ADEOS satellite (Table 2m). They first perform radiative
transfer calculations to predict top-of-atmosphere (TOA) radiances
measured in OCTS channels 1-8 (center wavelengths 0.412-0.865 μm). These
calculations use aerosol optical depths and scattering phase functions
derived from ground-based sun and sky radiometer measurements as
described by von Hoyningen-Huene et al. (1998; personal communication)
and summarized above. When they use the phase functions that best fit
their sky brightness measurements, they find root-mean-square
differences (RMSD) of \< 5% between calculated and OCTS-measured
radiances for OCTS channels 4-8 (0.520-0.865 μm), and somewhat larger
RMSD for channels 1-3. As noted above, these best-fit phase functions
are obtained using a scattering theory for nonspherical particles. In
contrast, using spherical-particle phase functions (for the marine
aerosol cases they consider) produces significantly different
relationships between TOA radiance and AOT. They report that using these
spherical-particle relationships in AOT retrievals from TOA radiances
would yield AOTs too large by a factor of \~2 in the near-infrared
channels (6-8). By using look-up tables of TOA radiance vs. AOT based on
their nonspherical particle phase functions they retrieve AOT spectra
over the ocean for OCTS channels 4-8 on three days (14, 16, and 18 June
1997). Results are presented as images of the Ångström fitting
parameters α and β defined by AOT(λ) = β (λ\[μm\])^--α^, where β is
AOT(1 μm). Comparisons of α and β values measured by sunphotometer at
Sagres-50, Sagres-500, and Sagres-900 with corresponding OCTS-retrieved
values at nearby pixels over the ocean yielded differences of typically
±0.2 in α and ±0.03 in β.

**4. Summary and conclusions**

CLEARCOLUMN provided a detailed data set of clear sky aerosol properties
at many surface sites of the ACE-2 area reaching from Tenerife to South
West Portugal and including ship borne measurements. The near-sea-level
data were complemented by measurements at mountain sites at different
altitudes up to 3570 m asl. Aircraft measurements connected the surface
based data and extended the data set in the vertical. The aerosol
characteristics are available for different air masses ranging from
clean marine air comparable to the ACE-1 environment to polluted air
masses from the European continent. In the southernmost part of the
working area, Saharan dust outbreaks were encountered on several
occasions. The combined data set includes the three-dimensional
variability of physical and chemical aerosol characteristics as a
function of particle size and aerosol type, thus providing the basic
information for regional assessments of aerosol effects.

While many of the aerosol characteristics were derived at reduced
relative humidities, large data sets on particle growth and change of
optical parameters with humidity were obtained at several sites and on
the Pelican aircraft. With that information the data set can in
principle be converted to ambient thermodynamic conditions. However, the
fact that particle growth measurements could usually be made only for
diameters up to 250 nm, coupled with some unexplained disagreements
between different measures of hygroscopic effects on light scattering,
calls for further study.

With the volumetric aerosol data several closure tests were made. At
Sagres-50 a 3-way comparison of size-resolved mass concentrations from
gravimetric, chemical, and number distributions (Neusüß et al., 2000)
produced agreement within state of the art experimental uncertainties
(estimated at ±20% for each method for mass integrated over all D~p~ \<
3 μm).

State of the art columnar optical aerosol measurements were made at the
CLEARCOLUMN sites. Beyond the usual spectral and angular parameters,
polarization characteristics were measured on Tenerife extending the
range of aerosol information and connecting the ground based optical
data to satellite borne polarisation measurements with the POLDER
instrument (Elias et al., 2000). At several surface and airborne
positions aerosol parameters were retrieved with different methodologies
from remotely sensed optical measurements with inversion and retrieval
algorithms, thus deriving ambient size distributions and intensive
particle properties such as their refractive index as a function of
aerosol types (e.g., von Hoyningen-Huene et al., 1998; personal
communication; Wagner et al., 1998; Schmid et al., 2000). In a few
experiments these derived aerosol properties were compared to volumetric
aerosol measurements to test the quality of the retrieval. Among the
difficulties in these comparisons were the technical limitations in
measuring supermicrometer aerosol properties from an aircraft.

CLEARCOLUMN determined aerosol single scattering albedos ω by a variety
of techniques in a wide range of aerosol conditions. Values determined
from dry (27% RH) aerosol light scattering and absorption measurements
at the Sagres-50 ground site in Portugal yielded ω(550 nm) = 0.94±0.02
and 0.93±0.02 for pollution outbreaks and "clean" periods, respectively
(Carrico et al., 2000). Considering measurement uncertainties and the
range of air masses and RH at Sagres-50, they estimate the range of
ambient ω(550 nm) there as 0.91 to 0.97. Shipboard measurements of
aerosol scattering and absorption at 55% RH yielded a somewhat larger
difference in ω(550 nm) between cases of continental flow and marine
flow, with values of 0.95±0.03 and 0.98±0.01, respectively (Quinn et
al., 2000). Also, ω derived from best fits of calculated to measured
solar radiative fluxes (von Hoyningen-Huene et al., 1998; personal
communication) yielded values for the hydrated, ambient column aerosol
of 0.90±0.04 for polluted continental cases and 0.98±0.03 for
maritime-influenced cases (both without African dust).

The differences in single scattering albedo obtained by different
techniques (e.g., 0.90±0.04 to 0.95±0.03 for nominally polluted cases)
may not be statistically significant given the quoted uncertainties and
variabilities. Nevertheless, aerosol single scattering albedos of 0.90
and 0.95 can yield significantly different aerosol climatic effects over
realistic surfaces (e.g., Haywood and Shine, 1995; Hansen et al., 1997;
Russell et al., 1997). Thus it is important to determine whether the
differences in ω reflect different aerosols or different measurement and
analysis techniques. This points to a need for increased emphasis in
future experiments on (a) simultaneous measurements of the same air mass
by different techniques, and (b) standardized methods of deriving ω
from, e.g., in situ scattering and absorption measurements (Anderson and
Ogren, 1998; Bond et al., 1999), so that measurements made at different
times and places can be compared directly.

ACE-2 tests of column closure produced a wide range of results. Tests
that produced relatively small discrepancies included comparisons of:
(1) African dust extinction and optical depth spectra (λ = 380 to 1060
nm) determined by airborne sunphotometer to those computed from measured
size distributions using multicomponent size-resolved compositions based
on ACE-2 measurements (Collins et al., 2000; Schmid et al., 2000), (2)
Aerosol optical depths for the humid marine boundary layer (RH\>80%) as
measured by sunphotometer to those retrieved from radiances measured by
the satellite sensors AVHRR and OCTS (Durkee et al., 2000; Schmid et
al., 2000; Livingston et al., 2000; von Hoyningen-Huene et al., 1999;
personal communication), and (3) African dust aerosol optical depth
profiles measured by airborne sunphotometer and retrieved from lidar
backscatter (Schmid et al., 2000). In tests of type (1) and (2) closure
degraded for (1) African dust extinction and optical depth at λ = 1558
nm, owing possibly to refractive index errors at that wavelength, (2a)
African dust optical depths at 630 and especially 860 nm, possibly
caused by particle shapes and complex refractive indices not accounted
for in AVHRR retrieval algorithms and (2b) Relatively dry (RH\<78%)
marine boundary layer optical depths, attributed to particle asphericity
not accounted for in OCTS retrieval algorithms.

In the marine boundary layer optical depths or extinctions from airborne
in situ measurements (particle size spectrometer, nephelometer,
absorption photometer) were typically less than those from the airborne
sunphotometer. Although differences between AODs from in situ size
distributions and from sunphotometer were judged to be within the
combined uncertainties, those uncertainties were significant (often
\~30% or larger) and arose from many sources (the most important of
which were, in most cases, uncertainties in sizing by mobility and
optical analyzers, in aerosol mixing state (internal vs. external), in
heating within the optical sizer, in the hygroscopicity of organics, and
spatiotemporal variations of optical depth on the moving path between
sunphotometer and sun). Differences between AODs from the
nephelometer/absorption photometer combination and from the
sunphotometer were larger still, probably because of large uncertainties
in inlet cyclone correction factors. Nevertheless, as pointed out by
Collins et al. (2000), the degree of agreement that was obtained in the
aircraft vertical profiles is significant, because of the variety of
instruments on board, each of which was sensitive to different aspects
of the sampled aerosol. Agreement among this variety of measures limits
the degree to which potential multiple errors in the size distribution
and related analyses could simply offset one another, as might be the
case if comparisons were limited to a single measurement at a single
wavelength.

It is noteworthy that in the great majority of the ACE-2 Pelican
comparisons, the sign of the AOD difference (∆AOD = AOD~in\ situ~ -
AOD~sunphotometer~) is negative, as was obtained in several previous
studies (e.g., Clarke et al., 1996; Hegg et al., 1997; Remer et al.,
1997; Hartley et al., 2000; Kato et al., A comparison of the aerosol
optical thickness derived from ground-based and airborne measurements,
submitted to *Journal of Geophysical Research*, 1999). Although reasons
for these differences are currently speculative, some phenomena reported
in the literature might provide at least partial explanations. These
phenomena include (a) loss of semivolatile material (e.g., organics) in
direct sampling (e.g., Eatough et al., 1996), (b) gas absorption that
might be present but is not accounted for in the sunphotometer analyses
(e.g., Halthore et al., 1998), and/or (c) aerosol hygroscopic changes
that can be greater than in the models used (e.g., Saxena et al., 1995).

Attempts to demonstrate closure between boundary layer optical depth
spectra from sunphotometer and from shipboard dry particle size
distributions grown using radiosonde humidity profiles often yielded
large discrepancies (Livingston et al., 2000). A primary reason is the
lack of validated hygroscopic growth models covering the necessary range
of particle sizes and compositions. In general ACE-2 results point to
unresolved differences between the hygroscopic changes in particle size
and light scattering described by various measurements and models.
Uncertainties in single scattering albedo also result in part from lack
of knowledge of the effects of changing humidity on aerosol light
absorption, another area that requires further investigation.

Taken together, the ACE-2 CLEARCOLUMN data set provides a large
collection of new information on the properties of the aerosol over the
northeast Atlantic Ocean. CLEARCOLUMN studies have also pointed to
improved techniques for analyzing current and future data sets
(including satellite data sets) that will provide a more accurate and
comprehensive description of the Atlantic-European-African aerosol.
Several ongoing studies to harmonize the underlying aerosol models used
by remote retrieval algorithms with the corresponding measured aerosol
properties will help in this regard. When these ongoing improvements and
validations are complete, the combined volumetric and columnar data sets
will provide the information for a regional quantification of radiative
forcing by anthropogenic aerosols.

**5. Acknowledgements**

This research was conducted as part of the second Aerosol
Characterization Experiment (ACE-2), which is a contribution to the
International Global Atmospheric Chemistry (IGAC) core project of the
International Geosphere-Biosphere Programme (IGBP). Financial support
for the measurements and analyses was provided by the DGXII of the
European Commission (contracts Nr. ENV4-CZ95-0032 and Nr.
ENV4-CT95-0108), by the Institute for Tropospheric Research, Leipzig,
the UK Meteorological Office, and by the US National Oceanic and
Atmospheric Administration, National Aeronautics and Space
Administration, National Science Foundation, and Office of Naval
Research. We gratefully acknowledge the extensive logistic support by
the station Radio Naval of Sagres, which hosted the central CLEARCOLUMN
site in the Sagres area.

REFERENCES

Anderson, T. L, and Ogren, J. A. 1998. Determining aerosol radiative
properties using the TSI 3563 integrating nephelometer. *Aer. Sci. Tech.
29*, 57-69.

Bates, T., Quinn, P., Covert, D. S., Coffman, D. J., and Johnson, D.
2000. Aerosol properties and controlling processes in the lower marine
boundary layer: A comparison of ACE-1 and ACE-2. *Tellus* B, this issue.

Bergstrom, R. W., and Russell, P. B. 1999. Estimation of aerosol
radiative effects over the mid-latitude North Atlantic region from
satellite and in situ measurements. *Geophys. Res. Lett*., *26*,
1731-1734.

Bond, T. C, Anderson, T. L., and Campbell, D. 1999. Calibration and
intercomparison of filter-based measurements of visible light absorption
by aerosols. *Aer. Sci. Tech. 30*, 582-600.

Brenguier, J.-L., and co-authors 2000. An overview of the ACE-2
CLOUDYCOLUMN closure experiment. *Tellus* B, this issue.

Bugalho, M.L., Silva, A.M., and von Hoyningen-Huene, W. 1998. Evaluation
of spectral aerosol properties from sun-photometry and nephelometer
measurements during ACE 2 CLEARCOLUMN. *J. Aerosol Sci.*, 29, S263-S264.

Carrico, C. M., Rood, M. J., Ogren, J. A., Neusüß, C., Wiedensohler, A.,
and Heintzenberg, J. 2000. Aerosol light scattering properties measured
at Sagres, Portugal, during ACE-2. *Tellus* B, this issue.

Clarke, A. D., Porter, J. N., Valero, F. P. J., and Pilewskie, P., 1966.
Vertical profiles, aerosol microphysics, and optical column closure
during the Atlantic Stratocumulus Transition Experiment: Measured and
modeled column optical properties. *J. Geophys. Res. 101*, 4443-4453.

Collins, D. R., Jonsson, H. H., Seinfeld, J. H., Flagan, R. C., Gassó,
S., Hegg, D., Russell, P. B., Livingston, J. M., Schmid, B., Öström, E.,
Noone, K. J., and Russell, L. M. 2000. In situ aerosol size
distributions and clear column radiative closure during ACE-2. *Tellus*
B, this issue.

Covert, D.S., Charlson, R. J. and Ahlquist, N.C. 1972. A study of the
relationship of chemical composition and humidity to light scattering by
aerosols. *J. App. Met. 11*, 968-976.

Durkee, P. A., Nielsen, K. E., Russell, P. B., Schmid, B., Livingston,
J. M., Collins, D., Flagan, R. C., Seinfeld, H. H., Noone, K. J.,
Öström, E., Gassó, S., Hegg, D., Bates, T. S., Quinn, P. K., and
Russell, L. M. 2000. Regional aerosol properties from satellite
observation: ACE-1, TARFOX and ACE-2 results. *Tellus* B, this issue.

Eatough, D. J., Eatough, D. A., and Lewis, E. A. 1995. Fine particulate
chemical composition and extinction apportionment at Canyonlands
National Park using organic particulate material concentrations obtained
with a multi-system, multichannel diffusion denuder sampler. *J.
Geophys. Res. **101***, 19515.

Elias, T., C, Devaux, P. Goloub, D. Tanré and M. Herman, 2000.
Polarising properties of the aerosols in the north-eastern tropical
Atlantic Ocean, with emphasis on the ACE-2 period, *Tellus* B, this
issue.

Fitzgerald, J.W., Hoppel, W.A. 1982. The size and scattering coefficient
of urban aerosol particles at Washington, DC as a function of relative
humidity.*, J. Atmos. Sci. 39, 1838-1852.*

Flamant, C., Pelon, J., Chazette, P., Trouillet, V., Bruneau, D., Quinn,
P., Frouin, R., Bruneau, D., Leon, J. F., Bates, T. Johnson, J., and
Livingston, J. 2000. Airborne lidar measurements of aerosol spatial
distribution and optical properties over the Atlantic Ocean during a
European pollution outbreak of ACE-2. *Tellus* B, this issue.

Formenti, P., Andreae, M. O., and Lelieveld, J. 2000. Measurements of
aerosol optical depth in the North Atlantic free troposphere: results
from ACE-2. *Tellus* B, this issue.

Gassó, S., Hegg, D. A., Covert, D. S., Noone, K., Öström, E., Schmid,
B., Russell, P. B., Livingston, J. M., Durkee, P. A., and Jonsson, H.
2000. Influence of humidity on the aerosol scattering coefficient and
its effect on the upwelling radiance during ACE-2. *Tellus* B, this
issue.

Halthore, R. N., Nemesure, S., Schwartz, S. E., Imre, D. G., Berk, A.,
Dutton, E. G., and Bergin, M. H. 1998. Models overestimate diffuse
clear-sky surface irradiance: A case for excess atmospheric absorption.
*Geophys. Res. Lett. **25***, 3591-3594.

Hansen, J. M., Sato, M., and Ruedy, R. 1997. Radiative forcing and
climate response. *J. Geophys. Res. 102*, 6831-6864.

Hartley, W. S., Hobbs, P. V., Ross, J. L., Russell, P. B., and
Livingston, J. M., 2000. Properties of aerosols aloft relevant to direct
radiative forcing off the mid-Atlantic coast of the United States. *J.
Geophys. Res.*, in press.

Haywood, J. M., and K. P. Shine, The effect of anthropogenic sulfate and
soot aerosol on the clear sky planetary radiation budget, Geophys. Res.
Lett., 22, 603-606, 1995.

Hegg, D. A. , Covert, D.S., Rood, M.J., Hobbs, P. V . 1996. Measurement
of the aerosol optical properties in marine air. *J. Geophys. Res., 96,
12883-12903.*

Hegg, D. A., Livingston, J., Hobbs, P. V., Novakov, T. and Russell, P.
B. 1997. Chemical apportionment of aerosol column optical depth off the
mid-Atlantic coast of the United States, *J. Geophys. Res., 102,*
25,293-25,303,.

Heintzenberg, J., Charlson, R. J., Clarke, A. D., Liousse, C.,
Ramaswamy, V., Shine, K. P., Wendisch, M. and Helas, G. 1997.
Measurements and modeling of aerosol single-scattering albedo: Progress,
problems, and prospects, *Beitr. Phy. Atmosph*., 70, 4, 249-263.

Henning, S., Weise, D., Birmili, W., Wiedensohler, A., and Covert, D. S.
1998. The particle size distribution and total number concentration for
different air masses at the south-western edge of Europe. J. Aerosol
Sci. **29**, S273-S274.

Howell, S. G., and Huebert, B. J., 1998. Determining marine and aerosol
scattering characteristics at ambient humidity from size-resolved
chemical composition. *J. Geophys. Res.* 103, 1391-1404.

Johnson, D., and co-authors 2000. LAGRANGIAN experiments in ACE-2: an
overview. *Tellus* B, this issue.

Kotchenruther, R.A., Hobs, P.V., Hegg, D. A. 1999. Humidification
factors for atmospheric aerosol off the mid-Atlantic coast of United
States. *J. Geophys. Res. , 104, No. D2, 2239-2251.*

Livingston, J. M., Kapustin, V. N., Schmid, B., Russell, P. B., Quinn,
P. K., Bates, T. S., Durkee, P. A., and Freudenthaler, V. 2000.
Shipboard sunphotometer measurements of aerosol optical depth spectra
and columnar water vapor during ACE-2. *Tellus* B, this issue.

Mishchenko, M. I., Travis, L. D., Kahn, R. A., and West, R. A. 1997.
Modeling phase functions for dustlike tropospheric aerosols using a
shape mixture of randomly oriented polydisperse spheroids. J. Geophys.
Res. 102, 16831-16847.

Neusüß, C., Weise, D., Birmili, W., Wiedensohler, A., and Covert, D.
2000. Size-Segregated Chemical, Gravimetric and Number Distribution
derived Mass Closure of the aerosol in Sagres, Portugal)during ACE-2.
*Tellus* B, this issue.

Novakov, T., Bates, T. S., and Quinn, P. K. 2000. Shipboard measurements
of the concentration and properties of carbon aerosols during ACE-2.
*Tellus* B, this issue.

Novakov, T., Hegg, D. A., and Hobbs, P. V. 1997. Airborne measurements
of carbonaceous aerosols on the east coast of the United States, *J.
Geophys. Res.*, *102* , 30,023-30,030.

Öström, E., and Noone, K. J. 2000. Vertical profiles of aerosol
scattering and absorption measured in situ during the North Atlantic
Aerosol Characterization Experiment ACE-2. *Tellus* B, this issue.

Philippin, S., Neusüß, C., Wiedensohler, A., Heintzenberg, J., Carrico,
C. M., and Rood, M. J. 1998. Optical properties of anthropogenically
influenced aerosols in a marine atmosphere: An optical closure
experiment. *J. Aer. Sci.* *29*, S1151-S1152.

Powell, D. M., Reagan, J. A., Rubio, M. A., Erxleben, W. H. and
Spinhirne. J. D. 2000. ACE-2 multiple angle Micro-Pulse Lidar
observations from Las Galletas, Tenerife, Canary Islands. *Tellus* B,
this issue.

Putaud, J. P., Van Dingenen, R., Mangoni, M., Virkkula, A., Raes, F.
Maring, H., Prospero, J.M., Swietlicki, E., Berg, O.H., Hillamo, R. and
Makela, T. 2000. Chemical mass closure and origin assessment of the
submicron aerosol in the marine boundary layer and the free troposphere
at Tenerife during ACE-2. *Tellus* B, this issue.

Quinn, P., Coffman, D. J., Bates, T. S., and Covert, D. S. 2000.
Chemical and optical properties of ACE-2 aerosol. *Tellus* B, this
issue.

Quinn, P. K., Anderson, T. L., Bates, T. S., Dlugi, R., Heintzenberg,
J., Hoyningen-Huene von, W., Kulmala, M., Russell, P. B., and
Swietlicki, E. 1996. Closure in tropospheric aerosol-climate research: a
review and future needs for addressing aerosol direct shortwave
radiative forcing. *Contr. Atmos. Phys.* **69**, 547-577.

Raes, F., Bates, T., Mcgovern, F., van Liedekerke, M., 2000. The Second
Aerosol Characterization Experiment (ACE-2): general overview and main
results. *Tellus* B, this issue.

Remer, L. A., Gassó, S., Hegg, D. A., Kaufman, Y. J., and Holben, B. N.
1997. Urban/industrial aerosol: Ground-based Sun/sky radiometer and
airborne in situ measurements, *J. Geophys. Res.* 102, 16,849-16,859.

Russell, P. B., Kinne, S., and Bergstrom, R. 1997. Aerosol climate
effects: Local radiative forcing and column closure experiments, *J.
Geophys. Res. 102*, 9397-9407.

Saxena, P., Hildemann, L. M., McMurry, P. H., and Seinfeld, J. H., 1995.
Organics alter hygroscopic behavior of atmospheric particles*. J.
Geophys. Res.100*, 18,755-18,770.

Schmeling, M., Russell, L. M., Erlick, C., Collins, D., Flagan, R. C.,
Seinfeld, J. H., Jonsson, H., Wang, Q., Kregsamer, P., and Streli, C.
2000. Aerosol particle chemical characteristics measured from aircraft
in the lower troposphere during ACE-2. *Tellus* B, this issue.

Schmid, B., Livingston, J. M., Russell, P. B., Durkee, P. A., Collins,
D. R., Flagan, R. C., Seinfeld, J. H., Gassó, S., Hegg, D. A., Öström,
E., Noone, K. J., Welton, E. J., Voss, K., Gordon, H. R., Formenti, P.,
and Andreae, M. O. 2000. Clear sky closure studies of lower tropospheric
aerosol and water vapor during ACE-2 using airborne sunphotometer,
airborne in-situ, space-borne, and ground-based measurements. *Tellus*
B, this issue.

Smirnov, A., Holben, B. N., Slutsker, I., Welton, E. J., and Formenti,
P. 1998. Optical properties of Saharan dust during ACE-2. *J. Geophys.
Res.* **103D**, 28079-28092.

Swietlicki, E., Zhou, J., Berg, O. H., Hameri, K., Vakeva, M., Makela,
J., Covert, D. S., Dusek, U., Busch, B., Wiedensohler, A., and
Stratmann, F. 2000. Hygroscopic properties of aerosol particles in the
eastern Northern Atlantic during ACE-2. *Tellus* B, this issue.

Tang, I. N., Tridico, A. C., and Fung, K. H., 1997. Thermodynamic and
optical properties of sea salt aerosols. J. Geophys. Res., 102,
23,269-23,275.

Tomasi, C., Marani, S., Vitale, V., Wagner, F., Cacciari, A., and
Lupi,A. 2000. Precipitable water evaluations from infrared
sun-photometric measurements analysed using the atmospheric hygrometry
technique. *Tellus* B, this issue.

Verver G., Raes, F., Vogelezang, D., Johnson, D. 2000. The second
AerosolCharacterization Experiment (ACE-2): meteorological and chemical
context, *Tellus*.

Vitale, V., Tomasi, C., von Hoyningen-Huene, W., Bonafe\', U., Marani,
S., Lupi, A., Cacciari, A., and Ruggeri, P. 2000. Spectral measurements
of aerosol particle extinction in the 0.4 - 3.7 um wavelength range,
performed at Sagres with the IR-RAD sun-radiometer. *Tellus* B, this
issue.

von Hoyningen-Huene, W., Schmidt, T., Herber, A., and Silva, A. M. 1998.
Climate-relevant columnar optical aerosol parameters obtained during
ACE-2 CLEARCOLUMN and their influence on the shortwave radiative
balance. *J. Aerosol Sci, 29*, S269-S270.

von Hoyningen-Huene, W., Schmidt, T., Freitag, M., Burrows, P., and
Silva, A. M. 1999. Closures between ground-based and spaceborne data for
the development of retrieval procedures for aerosols properties, *J.
Aerosol Sci, 30*, S431-S432.

Wagner, F., Müller, D., Ansmann, A., Weise, D., and Althausen, D. 1998.
*Comparison of aerosol properties derived from lidar, sun photometer and
in situ observations during the Aerosol Characterization Experiment 2*.
[19th International Laser Radar Conference]{.underline}, Annapolis,
NASA/CP-1998-207671/PT1, p.457-460.

Welton, E. J., Voss, K. J., Gordon, H. R., H. Maring, Smirnov, A.,
Holben, B., Schmid, B., Livingston, J. M., Russell, P. B., Durkee, P.
A., Formenti, P., Andreae, M. O., and Dubovik, O. 2000. Ground-based
lidar measurements of aerosols during ACE-2: Instrument description,
results, and comparisons with other ground-based and airborne
measurements. *Tellus* B, this issue.

Table 1 Coordinates of land sites used in CLEARCOLUMN

  ------------------------- ----------- ----------- ----------- ----------
  Site                      Acronym     Longitude   Latitude    Altitude
                                                                (m asl)

  Sagres-50                 S50         8º 57\'W    36º 59\'N   50

  Sagres-500                S500        8º 37\'W    36º 19\'N   500

  Sagres-900                S900        8º 37\'W    36º 19\'N   900

  Las Galletas              LG          16º 39\'W   28º 0\'N    25

  San Cristobal de La       SCLL        16º 29\'W   28º 29\'N   600
  Laguna                                                        

  Santa Cruz                SC          16º 14'W    28º 29'N    10

  Punta del Hidalgo         PDH         16º 19\'W   28º 34\'N   42

  Izaña                     IZO         16º 30\'W   28º 18\'N   2360

  Teide                     TEI         16º 36\'W   28º 16\'N   3570
  ------------------------- ----------- ----------- ----------- ----------

Table 2a Measurements made at the Sagres 50 site

+---+------------------------+----------------+-----------------+--------+
|   | Property measured      | Principal      | Institution     |        |
|   |                        | Investigator   |                 |        |
+---+------------------------+----------------+-----------------+--------+
| # |                        |                |                 |        |
| # |                        |                |                 |        |
| # |                        |                |                 |        |
|   |                        |                |                 |        |
| A |                        |                |                 |        |
| e |                        |                |                 |        |
| r |                        |                |                 |        |
| o |                        |                |                 |        |
| s |                        |                |                 |        |
| o |                        |                |                 |        |
| l |                        |                |                 |        |
|   |                        |                |                 |        |
| C |                        |                |                 |        |
| h |                        |                |                 |        |
| e |                        |                |                 |        |
| m |                        |                |                 |        |
| i |                        |                |                 |        |
| c |                        |                |                 |        |
| a |                        |                |                 |        |
| l |                        |                |                 |        |
+---+------------------------+----------------+-----------------+--------+
|   | Aerosol ionic mass,    | C. Neusüß      | Institute for   |        |
|   | size segregated        |                | Tropospheric    |        |
|   |                        |                | Research        |        |
+---+------------------------+----------------+-----------------+--------+
|   | Aerosol carbon mass,   | C. Neusüß      | Institute for   |        |
|   | size segregated        |                | Tropospheric    |        |
|   |                        |                | Research        |        |
+---+------------------------+----------------+-----------------+--------+
| * |                        |                |                 |        |
| A |                        |                |                 |        |
| e |                        |                |                 |        |
| r |                        |                |                 |        |
| o |                        |                |                 |        |
| s |                        |                |                 |        |
| o |                        |                |                 |        |
| l |                        |                |                 |        |
| P |                        |                |                 |        |
| h |                        |                |                 |        |
| y |                        |                |                 |        |
| s |                        |                |                 |        |
| i |                        |                |                 |        |
| c |                        |                |                 |        |
| a |                        |                |                 |        |
| l |                        |                |                 |        |
| A |                        |                |                 |        |
| n |                        |                |                 |        |
| d |                        |                |                 |        |
| O |                        |                |                 |        |
| p |                        |                |                 |        |
| t |                        |                |                 |        |
| i |                        |                |                 |        |
| c |                        |                |                 |        |
| a |                        |                |                 |        |
| l |                        |                |                 |        |
| * |                        |                |                 |        |
+---+------------------------+----------------+-----------------+--------+
|   | Aerosol size           | A.             | Institute for   |        |
|   | distributions (DMPS &  | Wiedensohler   | Tropospheric    |        |
|   | APS)                   |                | Research        |        |
+---+------------------------+----------------+-----------------+--------+
|   | Aerosol backscatter    | F. Wagner      | Institute for   |        |
|   | and extinction         |                | Tropospheric    |        |
|   | profiles (lidar)       |                | Research        |        |
+---+------------------------+----------------+-----------------+--------+
|   | RH controlled light    | M. Rood        | University of   |        |
|   | scattering             |                | Illinois        |        |
+---+------------------------+----------------+-----------------+--------+
|   | Aerosol optical depth  | V. Vitale      | FISBAT Bologna  |        |
|   | at 13 wavelengths      |                |                 |        |
|   | (IR-RAD)               |                |                 |        |
+---+------------------------+----------------+-----------------+--------+
|   | Ångström turbidity     | V. Vitale      | FISBAT Bologna  |        |
|   | parameter (IR-RAD)     |                |                 |        |
+---+------------------------+----------------+-----------------+--------+
|   | Aerosol optical depth  | V. Vitale      | FISBAT Bologna  |        |
|   | at 12 wavelengths      |                |                 |        |
|   | (UVISIR-1)             |                |                 |        |
+---+------------------------+----------------+-----------------+--------+
|   | Ångström turbidity     | V. Vitale      | FISBAT Bologna  |        |
|   | parameter (UVISIR-1)   |                |                 |        |
+---+------------------------+----------------+-----------------+--------+
|   | Aerosol optical depth  | W. von         | University of   |        |
|   | at 10 wavelengths (sun | H              | Leipzig         |        |
|   | and star photometry)   | oyningen-Huene |                 |        |
+---+------------------------+----------------+-----------------+--------+
|   | Ångström turbidity     | W. von         | University of   |        |
|   | (sun and star          | H              | Leipzig         |        |
|   | photometry)            | oyningen-Huene |                 |        |
+---+------------------------+----------------+-----------------+--------+
|   | Normalized sky         | W. von         | University of   |        |
|   | brightness             | H              | Leipzig         |        |
|   |                        | oyningen-Huene |                 |        |
+---+------------------------+----------------+-----------------+--------+

+---+------------------------+----------------+-----------------+--------+
|   | Property measured      | Principal      | Institution     |        |
|   |                        | Investigator   |                 |        |
+---+------------------------+----------------+-----------------+--------+
| # |                        |                |                 |        |
| # |                        |                |                 |        |
|   |                        |                |                 |        |
| M |                        |                |                 |        |
| e |                        |                |                 |        |
| t |                        |                |                 |        |
| e |                        |                |                 |        |
| o |                        |                |                 |        |
| r |                        |                |                 |        |
| o |                        |                |                 |        |
| l |                        |                |                 |        |
| o |                        |                |                 |        |
| g |                        |                |                 |        |
| i |                        |                |                 |        |
| c |                        |                |                 |        |
| a |                        |                |                 |        |
| l |                        |                |                 |        |
|   |                        |                |                 |        |
| A |                        |                |                 |        |
| n |                        |                |                 |        |
| d |                        |                |                 |        |
|   |                        |                |                 |        |
| O |                        |                |                 |        |
| t |                        |                |                 |        |
| h |                        |                |                 |        |
| e |                        |                |                 |        |
| r |                        |                |                 |        |
| s |                        |                |                 |        |
+---+------------------------+----------------+-----------------+--------+
|   | Vertical wind profiles | M. L. Bugalho  | University of   |        |
|   | (SODAR)                |                | Evora           |        |
+---+------------------------+----------------+-----------------+--------+
|   | Surface meteorology    | M. L. Bugalho  | University of   |        |
|   |                        |                | Evora           |        |
+---+------------------------+----------------+-----------------+--------+
|   | Radio soundings        | F. Wagner      | Institute for   |        |
|   | (Sagres)               |                | Tropospheric    |        |
|   |                        |                | Research        |        |
+---+------------------------+----------------+-----------------+--------+
|   | Radio soundings (S.    | M. L. Bugalho  | University of   |        |
|   | Teotonio)              |                | Evora           |        |
+---+------------------------+----------------+-----------------+--------+
|   | Radiative fluxes       | A. M. Silva,   | University of   |        |
|   | (downwelling global    |                | Evora           |        |
|   | and diffuse)           | W. von         |                 |        |
|   |                        | H              | University of   |        |
|   |                        | oyningen-Huene | Leipzig         |        |
+---+------------------------+----------------+-----------------+--------+

Table 2b. Measurements made at the Sagres-500 site

+---+------------------------+----------------+----------------------+---+
|   | Property measured      | Principal      | Institution          |   |
|   |                        | Investigator   |                      |   |
+---+------------------------+----------------+----------------------+---+
| # |                        |                |                      |   |
| # |                        |                |                      |   |
|   |                        |                |                      |   |
| A |                        |                |                      |   |
| e |                        |                |                      |   |
| r |                        |                |                      |   |
| o |                        |                |                      |   |
| s |                        |                |                      |   |
| o |                        |                |                      |   |
| l |                        |                |                      |   |
|   |                        |                |                      |   |
| o |                        |                |                      |   |
| p |                        |                |                      |   |
| t |                        |                |                      |   |
| i |                        |                |                      |   |
| c |                        |                |                      |   |
| a |                        |                |                      |   |
| l |                        |                |                      |   |
+---+------------------------+----------------+----------------------+---+
|   | Aerosol optical depth  | V. Vitale      | FISBAT Bologna       |   |
|   | at 7 wavelengths       |                |                      |   |
|   | (UVISIR-2)             |                |                      |   |
+---+------------------------+----------------+----------------------+---+
|   | Ångström turbidity     | V. Vitale      | FISBAT Bologna       |   |
|   | parameter (UVISIR-2)   |                |                      |   |
+---+------------------------+----------------+----------------------+---+
|   | Aerosol optical depth  | W. von         | University of        |   |
|   | at 10 wavelengths (sun | H              | Leipzig              |   |
|   | photometry)            | oyningen-Huene |                      |   |
+---+------------------------+----------------+----------------------+---+
|   | Ångström turbidity     | W. von         | University of        |   |
|   | (sun photometry)       | H              | Leipzig              |   |
|   |                        | oyningen-Huene |                      |   |
+---+------------------------+----------------+----------------------+---+
|   | Normalized sky         | W. von         | University of        |   |
|   | brightness             | H              | Leipzig              |   |
|   |                        | oyningen-Huene |                      |   |
+---+------------------------+----------------+----------------------+---+

Table 2c*. Measurements made at the Sagres 900 site*

+---+---+------------------------+---+----------------+---+----------------+---+---------+
|   |   | Property measured      | P |                | I |                |   |         |
|   |   |                        | r |                | n |                |   |         |
|   |   |                        | i |                | s |                |   |         |
|   |   |                        | n |                | t |                |   |         |
|   |   |                        | c |                | i |                |   |         |
|   |   |                        | i |                | t |                |   |         |
|   |   |                        | p |                | u |                |   |         |
|   |   |                        | a |                | t |                |   |         |
|   |   |                        | l |                | i |                |   |         |
|   |   |                        | I |                | o |                |   |         |
|   |   |                        | n |                | n |                |   |         |
|   |   |                        | v |                |   |                |   |         |
|   |   |                        | e |                |   |                |   |         |
|   |   |                        | s |                |   |                |   |         |
|   |   |                        | t |                |   |                |   |         |
|   |   |                        | i |                |   |                |   |         |
|   |   |                        | g |                |   |                |   |         |
|   |   |                        | a |                |   |                |   |         |
|   |   |                        | t |                |   |                |   |         |
|   |   |                        | o |                |   |                |   |         |
|   |   |                        | r |                |   |                |   |         |
+---+---+------------------------+---+----------------+---+----------------+---+---------+
| # |   |                        |   |                |   |                |   |         |
| # |   |                        |   |                |   |                |   |         |
|   |   |                        |   |                |   |                |   |         |
| A |   |                        |   |                |   |                |   |         |
| e |   |                        |   |                |   |                |   |         |
| r |   |                        |   |                |   |                |   |         |
| o |   |                        |   |                |   |                |   |         |
| s |   |                        |   |                |   |                |   |         |
| o |   |                        |   |                |   |                |   |         |
| l |   |                        |   |                |   |                |   |         |
|   |   |                        |   |                |   |                |   |         |
| C |   |                        |   |                |   |                |   |         |
| h |   |                        |   |                |   |                |   |         |
| e |   |                        |   |                |   |                |   |         |
| m |   |                        |   |                |   |                |   |         |
| i |   |                        |   |                |   |                |   |         |
| c |   |                        |   |                |   |                |   |         |
| a |   |                        |   |                |   |                |   |         |
| l |   |                        |   |                |   |                |   |         |
+---+---+------------------------+---+----------------+---+----------------+---+---------+
|   |   | Aerosol ionic mass     | C |                | I |                |   |         |
|   |   | (PM-10 sampler)        | . |                | n |                |   |         |
|   |   |                        | N |                | s |                |   |         |
|   |   |                        | e |                | t |                |   |         |
|   |   |                        | u |                | i |                |   |         |
|   |   |                        | s |                | t |                |   |         |
|   |   |                        | ü |                | u |                |   |         |
|   |   |                        | ß |                | t |                |   |         |
|   |   |                        |   |                | e |                |   |         |
|   |   |                        |   |                | f |                |   |         |
|   |   |                        |   |                | o |                |   |         |
|   |   |                        |   |                | r |                |   |         |
|   |   |                        |   |                | T |                |   |         |
|   |   |                        |   |                | r |                |   |         |
|   |   |                        |   |                | o |                |   |         |
|   |   |                        |   |                | p |                |   |         |
|   |   |                        |   |                | o |                |   |         |
|   |   |                        |   |                | s |                |   |         |
|   |   |                        |   |                | p |                |   |         |
|   |   |                        |   |                | h |                |   |         |
|   |   |                        |   |                | e |                |   |         |
|   |   |                        |   |                | r |                |   |         |
|   |   |                        |   |                | i |                |   |         |
|   |   |                        |   |                | c |                |   |         |
|   |   |                        |   |                | R |                |   |         |
|   |   |                        |   |                | e |                |   |         |
|   |   |                        |   |                | s |                |   |         |
|   |   |                        |   |                | e |                |   |         |
|   |   |                        |   |                | a |                |   |         |
|   |   |                        |   |                | r |                |   |         |
|   |   |                        |   |                | c |                |   |         |
|   |   |                        |   |                | h |                |   |         |
+---+---+------------------------+---+----------------+---+----------------+---+---------+
| # |   |                        |   |                |   |                |   |         |
| # |   |                        |   |                |   |                |   |         |
|   |   |                        |   |                |   |                |   |         |
| A |   |                        |   |                |   |                |   |         |
| e |   |                        |   |                |   |                |   |         |
| r |   |                        |   |                |   |                |   |         |
| o |   |                        |   |                |   |                |   |         |
| s |   |                        |   |                |   |                |   |         |
| o |   |                        |   |                |   |                |   |         |
| l |   |                        |   |                |   |                |   |         |
|   |   |                        |   |                |   |                |   |         |
| P |   |                        |   |                |   |                |   |         |
| h |   |                        |   |                |   |                |   |         |
| y |   |                        |   |                |   |                |   |         |
| s |   |                        |   |                |   |                |   |         |
| i |   |                        |   |                |   |                |   |         |
| c |   |                        |   |                |   |                |   |         |
| a |   |                        |   |                |   |                |   |         |
| l |   |                        |   |                |   |                |   |         |
|   |   |                        |   |                |   |                |   |         |
| A |   |                        |   |                |   |                |   |         |
| n |   |                        |   |                |   |                |   |         |
| d |   |                        |   |                |   |                |   |         |
|   |   |                        |   |                |   |                |   |         |
| O |   |                        |   |                |   |                |   |         |
| p |   |                        |   |                |   |                |   |         |
| t |   |                        |   |                |   |                |   |         |
| i |   |                        |   |                |   |                |   |         |
| c |   |                        |   |                |   |                |   |         |
| a |   |                        |   |                |   |                |   |         |
| l |   |                        |   |                |   |                |   |         |
+---+---+------------------------+---+----------------+---+----------------+---+---------+
|   | A |                        | A |                | I |                |   |         |
|   | e |                        | . |                | n |                |   |         |
|   | r |                        | W |                | s |                |   |         |
|   | o |                        | i |                | t |                |   |         |
|   | s |                        | e |                | i |                |   |         |
|   | o |                        | d |                | t |                |   |         |
|   | l |                        | e |                | u |                |   |         |
|   | s |                        | n |                | t |                |   |         |
|   | i |                        | s |                | e |                |   |         |
|   | z |                        | o |                | f |                |   |         |
|   | e |                        | h |                | o |                |   |         |
|   | d |                        | l |                | r |                |   |         |
|   | i |                        | e |                | T |                |   |         |
|   | s |                        | r |                | r |                |   |         |
|   | t |                        |   |                | o |                |   |         |
|   | r |                        |   |                | p |                |   |         |
|   | i |                        |   |                | o |                |   |         |
|   | b |                        |   |                | s |                |   |         |
|   | u |                        |   |                | p |                |   |         |
|   | t |                        |   |                | h |                |   |         |
|   | i |                        |   |                | e |                |   |         |
|   | o |                        |   |                | r |                |   |         |
|   | n |                        |   |                | i |                |   |         |
|   | ( |                        |   |                | c |                |   |         |
|   | D |                        |   |                | R |                |   |         |
|   | M |                        |   |                | e |                |   |         |
|   | P |                        |   |                | s |                |   |         |
|   | S |                        |   |                | e |                |   |         |
|   | ) |                        |   |                | a |                |   |         |
|   |   |                        |   |                | r |                |   |         |
|   |   |                        |   |                | c |                |   |         |
|   |   |                        |   |                | h |                |   |         |
+---+---+------------------------+---+----------------+---+----------------+---+---------+
|   | A |                        | A |                | U |                |   |         |
|   | e |                        | . |                | n |                |   |         |
|   | r |                        | M |                | i |                |   |         |
|   | o |                        | . |                | v |                |   |         |
|   | s |                        | S |                | e |                |   |         |
|   | o |                        | i |                | r |                |   |         |
|   | l |                        | l |                | s |                |   |         |
|   | a |                        | v |                | i |                |   |         |
|   | b |                        | a |                | t |                |   |         |
|   | s |                        | , |                | y |                |   |         |
|   | o |                        | M |                | o |                |   |         |
|   | r |                        | . |                | f |                |   |         |
|   | p |                        | L |                | E |                |   |         |
|   | t |                        | . |                | v |                |   |         |
|   | i |                        | B |                | o |                |   |         |
|   | o |                        | u |                | r |                |   |         |
|   | n |                        | g |                | a |                |   |         |
|   | c |                        | a |                |   |                |   |         |
|   | o |                        | l |                |   |                |   |         |
|   | e |                        | h |                |   |                |   |         |
|   | f |                        | o |                |   |                |   |         |
|   | f |                        |   |                |   |                |   |         |
|   | i |                        |   |                |   |                |   |         |
|   | c |                        |   |                |   |                |   |         |
|   | i |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | n |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
+---+---+------------------------+---+----------------+---+----------------+---+---------+
|   | A |                        | V |                | F |                |   |         |
|   | e |                        | . |                | I |                |   |         |
|   | r |                        | V |                | S |                |   |         |
|   | o |                        | i |                | B |                |   |         |
|   | s |                        | t |                | A |                |   |         |
|   | o |                        | a |                | T |                |   |         |
|   | l |                        | l |                | B |                |   |         |
|   | o |                        | e |                | o |                |   |         |
|   | p |                        |   |                | l |                |   |         |
|   | t |                        |   |                | o |                |   |         |
|   | i |                        |   |                | g |                |   |         |
|   | c |                        |   |                | n |                |   |         |
|   | a |                        |   |                | a |                |   |         |
|   | l |                        |   |                |   |                |   |         |
|   | d |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | p |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | h |                        |   |                |   |                |   |         |
|   | a |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | 1 |                        |   |                |   |                |   |         |
|   | 2 |                        |   |                |   |                |   |         |
|   | w |                        |   |                |   |                |   |         |
|   | a |                        |   |                |   |                |   |         |
|   | v |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | l |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | n |                        |   |                |   |                |   |         |
|   | g |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | h |                        |   |                |   |                |   |         |
|   | s |                        |   |                |   |                |   |         |
|   | ( |                        |   |                |   |                |   |         |
|   | U |                        |   |                |   |                |   |         |
|   | V |                        |   |                |   |                |   |         |
|   | I |                        |   |                |   |                |   |         |
|   | S |                        |   |                |   |                |   |         |
|   | I |                        |   |                |   |                |   |         |
|   | R |                        |   |                |   |                |   |         |
|   | - |                        |   |                |   |                |   |         |
|   | 1 |                        |   |                |   |                |   |         |
|   | ) |                        |   |                |   |                |   |         |
+---+---+------------------------+---+----------------+---+----------------+---+---------+
|   | Å |                        | V |                | F |                |   |         |
|   | n |                        | . |                | I |                |   |         |
|   | g |                        | V |                | S |                |   |         |
|   | s |                        | i |                | B |                |   |         |
|   | t |                        | t |                | A |                |   |         |
|   | r |                        | a |                | T |                |   |         |
|   | ö |                        | l |                | B |                |   |         |
|   | m |                        | e |                | o |                |   |         |
|   | t |                        |   |                | l |                |   |         |
|   | u |                        |   |                | o |                |   |         |
|   | r |                        |   |                | g |                |   |         |
|   | b |                        |   |                | n |                |   |         |
|   | i |                        |   |                | a |                |   |         |
|   | d |                        |   |                |   |                |   |         |
|   | i |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | y |                        |   |                |   |                |   |         |
|   | p |                        |   |                |   |                |   |         |
|   | a |                        |   |                |   |                |   |         |
|   | r |                        |   |                |   |                |   |         |
|   | a |                        |   |                |   |                |   |         |
|   | m |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | r |                        |   |                |   |                |   |         |
|   | ( |                        |   |                |   |                |   |         |
|   | U |                        |   |                |   |                |   |         |
|   | V |                        |   |                |   |                |   |         |
|   | I |                        |   |                |   |                |   |         |
|   | S |                        |   |                |   |                |   |         |
|   | I |                        |   |                |   |                |   |         |
|   | R |                        |   |                |   |                |   |         |
|   | - |                        |   |                |   |                |   |         |
|   | 1 |                        |   |                |   |                |   |         |
|   | ) |                        |   |                |   |                |   |         |
+---+---+------------------------+---+----------------+---+----------------+---+---------+
|   | A |                        | M |                | U |                |   |         |
|   | e |                        | . |                | n |                |   |         |
|   | r |                        | J |                | i |                |   |         |
|   | o |                        | . |                | v |                |   |         |
|   | s |                        | C |                | e |                |   |         |
|   | o |                        | o |                | r |                |   |         |
|   | l |                        | s |                | s |                |   |         |
|   | o |                        | t |                | i |                |   |         |
|   | p |                        | a |                | t |                |   |         |
|   | t |                        | , |                | y |                |   |         |
|   | i |                        |   |                | o |                |   |         |
|   | c |                        | A |                | f |                |   |         |
|   | a |                        | . |                | E |                |   |         |
|   | l |                        | M |                | v |                |   |         |
|   | d |                        | . |                | o |                |   |         |
|   | e |                        | S |                | r |                |   |         |
|   | p |                        | i |                | a |                |   |         |
|   | t |                        | l |                |   |                |   |         |
|   | h |                        | v |                |   |                |   |         |
|   | a |                        | a |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | 1 |                        |   |                |   |                |   |         |
|   | 4 |                        |   |                |   |                |   |         |
|   | w |                        |   |                |   |                |   |         |
|   | a |                        |   |                |   |                |   |         |
|   | v |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | l |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | n |                        |   |                |   |                |   |         |
|   | g |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | h |                        |   |                |   |                |   |         |
|   | s |                        |   |                |   |                |   |         |
|   | ( |                        |   |                |   |                |   |         |
|   | s |                        |   |                |   |                |   |         |
|   | u |                        |   |                |   |                |   |         |
|   | n |                        |   |                |   |                |   |         |
|   | p |                        |   |                |   |                |   |         |
|   | h |                        |   |                |   |                |   |         |
|   | o |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | o |                        |   |                |   |                |   |         |
|   | m |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | r |                        |   |                |   |                |   |         |
|   | y |                        |   |                |   |                |   |         |
|   | ) |                        |   |                |   |                |   |         |
+---+---+------------------------+---+----------------+---+----------------+---+---------+
|   | A |                        | M |                | U |                |   |         |
|   | e |                        | . |                | n |                |   |         |
|   | r |                        | B |                | i |                |   |         |
|   | o |                        | u |                | v |                |   |         |
|   | s |                        | g |                | e |                |   |         |
|   | o |                        | a |                | r |                |   |         |
|   | l |                        | l |                | s |                |   |         |
|   | s |                        | h |                | i |                |   |         |
|   | c |                        | o |                | t |                |   |         |
|   | a |                        | , |                | y |                |   |         |
|   | t |                        |   |                | o |                |   |         |
|   | t |                        | A |                | f |                |   |         |
|   | e |                        | . |                | E |                |   |         |
|   | r |                        | M |                | v |                |   |         |
|   | i |                        | . |                | o |                |   |         |
|   | n |                        | S |                | r |                |   |         |
|   | g |                        | i |                | a |                |   |         |
|   | a |                        | l |                |   |                |   |         |
|   | n |                        | v |                |   |                |   |         |
|   | d |                        | a |                |   |                |   |         |
|   | b |                        |   |                |   |                |   |         |
|   | a |                        |   |                |   |                |   |         |
|   | c |                        |   |                |   |                |   |         |
|   | k |                        |   |                |   |                |   |         |
|   | s |                        |   |                |   |                |   |         |
|   | c |                        |   |                |   |                |   |         |
|   | a |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | r |                        |   |                |   |                |   |         |
|   | i |                        |   |                |   |                |   |         |
|   | n |                        |   |                |   |                |   |         |
|   | g |                        |   |                |   |                |   |         |
|   | c |                        |   |                |   |                |   |         |
|   | o |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | f |                        |   |                |   |                |   |         |
|   | f |                        |   |                |   |                |   |         |
|   | i |                        |   |                |   |                |   |         |
|   | c |                        |   |                |   |                |   |         |
|   | i |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | n |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | s |                        |   |                |   |                |   |         |
|   | a |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | 3 |                        |   |                |   |                |   |         |
|   | w |                        |   |                |   |                |   |         |
|   | a |                        |   |                |   |                |   |         |
|   | v |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | l |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | n |                        |   |                |   |                |   |         |
|   | g |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | h |                        |   |                |   |                |   |         |
|   | s |                        |   |                |   |                |   |         |
+---+---+------------------------+---+----------------+---+----------------+---+---------+
|   | A |                        | W |                | U |                |   |         |
|   | e |                        | . |                | n |                |   |         |
|   | r |                        | v |                | i |                |   |         |
|   | o |                        | o |                | v |                |   |         |
|   | s |                        | n |                | e |                |   |         |
|   | o |                        | H |                | r |                |   |         |
|   | l |                        | o |                | s |                |   |         |
|   | o |                        | y |                | i |                |   |         |
|   | p |                        | n |                | t |                |   |         |
|   | t |                        | i |                | y |                |   |         |
|   | i |                        | n |                | o |                |   |         |
|   | c |                        | g |                | f |                |   |         |
|   | a |                        | e |                | L |                |   |         |
|   | l |                        | n |                | e |                |   |         |
|   | d |                        | - |                | i |                |   |         |
|   | e |                        | H |                | p |                |   |         |
|   | p |                        | u |                | z |                |   |         |
|   | t |                        | e |                | i |                |   |         |
|   | h |                        | n |                | g |                |   |         |
|   | a |                        | e |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | 1 |                        |   |                |   |                |   |         |
|   | 0 |                        |   |                |   |                |   |         |
|   | w |                        |   |                |   |                |   |         |
|   | a |                        |   |                |   |                |   |         |
|   | v |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | l |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | n |                        |   |                |   |                |   |         |
|   | g |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | h |                        |   |                |   |                |   |         |
|   | s |                        |   |                |   |                |   |         |
|   | ( |                        |   |                |   |                |   |         |
|   | s |                        |   |                |   |                |   |         |
|   | u |                        |   |                |   |                |   |         |
|   | n |                        |   |                |   |                |   |         |
|   | p |                        |   |                |   |                |   |         |
|   | h |                        |   |                |   |                |   |         |
|   | o |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | o |                        |   |                |   |                |   |         |
|   | m |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | r |                        |   |                |   |                |   |         |
|   | y |                        |   |                |   |                |   |         |
|   | ) |                        |   |                |   |                |   |         |
+---+---+------------------------+---+----------------+---+----------------+---+---------+
|   | Å |                        | W |                | U |                |   |         |
|   | n |                        | . |                | n |                |   |         |
|   | g |                        | v |                | i |                |   |         |
|   | s |                        | o |                | v |                |   |         |
|   | t |                        | n |                | e |                |   |         |
|   | r |                        | H |                | r |                |   |         |
|   | ö |                        | o |                | s |                |   |         |
|   | m |                        | y |                | i |                |   |         |
|   | t |                        | n |                | t |                |   |         |
|   | u |                        | i |                | y |                |   |         |
|   | r |                        | n |                | o |                |   |         |
|   | b |                        | g |                | f |                |   |         |
|   | i |                        | e |                | L |                |   |         |
|   | d |                        | n |                | e |                |   |         |
|   | i |                        | - |                | i |                |   |         |
|   | t |                        | H |                | p |                |   |         |
|   | y |                        | u |                | z |                |   |         |
|   | ( |                        | e |                | i |                |   |         |
|   | s |                        | n |                | g |                |   |         |
|   | u |                        | e |                |   |                |   |         |
|   | n |                        |   |                |   |                |   |         |
|   | p |                        |   |                |   |                |   |         |
|   | h |                        |   |                |   |                |   |         |
|   | o |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | o |                        |   |                |   |                |   |         |
|   | m |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | r |                        |   |                |   |                |   |         |
|   | y |                        |   |                |   |                |   |         |
|   | ) |                        |   |                |   |                |   |         |
+---+---+------------------------+---+----------------+---+----------------+---+---------+
|   | N |                        |   | W. von         |   | University of  |   |         |
|   | o |                        |   | H              |   | Leipzig        |   |         |
|   | r |                        |   | oyningen-Huene |   |                |   |         |
|   | m |                        |   |                |   |                |   |         |
|   | a |                        |   |                |   |                |   |         |
|   | l |                        |   |                |   |                |   |         |
|   | i |                        |   |                |   |                |   |         |
|   | z |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | d |                        |   |                |   |                |   |         |
|   | s |                        |   |                |   |                |   |         |
|   | k |                        |   |                |   |                |   |         |
|   | y |                        |   |                |   |                |   |         |
|   | b |                        |   |                |   |                |   |         |
|   | r |                        |   |                |   |                |   |         |
|   | i |                        |   |                |   |                |   |         |
|   | g |                        |   |                |   |                |   |         |
|   | h |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | n |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | s |                        |   |                |   |                |   |         |
|   | s |                        |   |                |   |                |   |         |
+---+---+------------------------+---+----------------+---+----------------+---+---------+
| # |   |                        |   |                |   |                |   |         |
| # |   |                        |   |                |   |                |   |         |
| # |   |                        |   |                |   |                |   |         |
| # |   |                        |   |                |   |                |   |         |
| # |   |                        |   |                |   |                |   |         |
| # |   |                        |   |                |   |                |   |         |
|   |   |                        |   |                |   |                |   |         |
| M |   |                        |   |                |   |                |   |         |
| e |   |                        |   |                |   |                |   |         |
| t |   |                        |   |                |   |                |   |         |
| e |   |                        |   |                |   |                |   |         |
| o |   |                        |   |                |   |                |   |         |
| r |   |                        |   |                |   |                |   |         |
| o |   |                        |   |                |   |                |   |         |
| l |   |                        |   |                |   |                |   |         |
| o |   |                        |   |                |   |                |   |         |
| g |   |                        |   |                |   |                |   |         |
| i |   |                        |   |                |   |                |   |         |
| c |   |                        |   |                |   |                |   |         |
| a |   |                        |   |                |   |                |   |         |
| l |   |                        |   |                |   |                |   |         |
|   |   |                        |   |                |   |                |   |         |
| A |   |                        |   |                |   |                |   |         |
| n |   |                        |   |                |   |                |   |         |
| d |   |                        |   |                |   |                |   |         |
|   |   |                        |   |                |   |                |   |         |
| O |   |                        |   |                |   |                |   |         |
| t |   |                        |   |                |   |                |   |         |
| h |   |                        |   |                |   |                |   |         |
| e |   |                        |   |                |   |                |   |         |
| r |   |                        |   |                |   |                |   |         |
| s |   |                        |   |                |   |                |   |         |
+---+---+------------------------+---+----------------+---+----------------+---+---------+
|   | 4 |                        | M |                |   | University of  |   |         |
|   | 8 |                        | . |                |   | Evora          |   |         |
|   | h |                        | B |                |   |                |   |         |
|   | o |                        | u |                |   |                |   |         |
|   | u |                        | g |                |   |                |   |         |
|   | r |                        | a |                |   |                |   |         |
|   | b |                        | l |                |   |                |   |         |
|   | a |                        | h |                |   |                |   |         |
|   | c |                        | o |                |   |                |   |         |
|   | k |                        | , |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | r |                        | A |                |   |                |   |         |
|   | a |                        | . |                |   |                |   |         |
|   | j |                        | M |                |   |                |   |         |
|   | e |                        | . |                |   |                |   |         |
|   | c |                        | S |                |   |                |   |         |
|   | t |                        | i |                |   |                |   |         |
|   | o |                        | l |                |   |                |   |         |
|   | r |                        | v |                |   |                |   |         |
|   | i |                        | a |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | s |                        |   |                |   |                |   |         |
|   | ( |                        |   |                |   |                |   |         |
|   | 8 |                        |   |                |   |                |   |         |
|   | 0 |                        |   |                |   |                |   |         |
|   | 0 |                        |   |                |   |                |   |         |
|   | , |                        |   |                |   |                |   |         |
|   | 9 |                        |   |                |   |                |   |         |
|   | 2 |                        |   |                |   |                |   |         |
|   | 5 |                        |   |                |   |                |   |         |
|   | , |                        |   |                |   |                |   |         |
|   | 1 |                        |   |                |   |                |   |         |
|   | 0 |                        |   |                |   |                |   |         |
|   | 0 |                        |   |                |   |                |   |         |
|   | 0 |                        |   |                |   |                |   |         |
|   | h |                        |   |                |   |                |   |         |
|   | P |                        |   |                |   |                |   |         |
|   | a |                        |   |                |   |                |   |         |
|   | ) |                        |   |                |   |                |   |         |
|   | a |                        |   |                |   |                |   |         |
|   | n |                        |   |                |   |                |   |         |
|   | d |                        |   |                |   |                |   |         |
|   | m |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | o |                        |   |                |   |                |   |         |
|   | r |                        |   |                |   |                |   |         |
|   | o |                        |   |                |   |                |   |         |
|   | l |                        |   |                |   |                |   |         |
|   | o |                        |   |                |   |                |   |         |
|   | g |                        |   |                |   |                |   |         |
|   | i |                        |   |                |   |                |   |         |
|   | c |                        |   |                |   |                |   |         |
|   | a |                        |   |                |   |                |   |         |
|   | l |                        |   |                |   |                |   |         |
|   | a |                        |   |                |   |                |   |         |
|   | n |                        |   |                |   |                |   |         |
|   | a |                        |   |                |   |                |   |         |
|   | l |                        |   |                |   |                |   |         |
|   | y |                        |   |                |   |                |   |         |
|   | s |                        |   |                |   |                |   |         |
|   | i |                        |   |                |   |                |   |         |
|   | s |                        |   |                |   |                |   |         |
|   | ( |                        |   |                |   |                |   |         |
|   | 9 |                        |   |                |   |                |   |         |
|   | 2 |                        |   |                |   |                |   |         |
|   | 5 |                        |   |                |   |                |   |         |
|   | , |                        |   |                |   |                |   |         |
|   | 1 |                        |   |                |   |                |   |         |
|   | 0 |                        |   |                |   |                |   |         |
|   | 0 |                        |   |                |   |                |   |         |
|   | 0 |                        |   |                |   |                |   |         |
|   | h |                        |   |                |   |                |   |         |
|   | P |                        |   |                |   |                |   |         |
|   | a |                        |   |                |   |                |   |         |
|   | ) |                        |   |                |   |                |   |         |
+---+---+------------------------+---+----------------+---+----------------+---+---------+
|   | R |                        |   | A. M. Silva,   |   | University of  |   |         |
|   | a |                        |   |                |   | Evora          |   |         |
|   | d |                        |   | W. von         |   |                |   |         |
|   | i |                        |   | H              |   | University of  |   |         |
|   | a |                        |   | oyningen-Huene |   | Leipzig        |   |         |
|   | t |                        |   |                |   |                |   |         |
|   | i |                        |   |                |   |                |   |         |
|   | v |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | f |                        |   |                |   |                |   |         |
|   | l |                        |   |                |   |                |   |         |
|   | u |                        |   |                |   |                |   |         |
|   | x |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | s |                        |   |                |   |                |   |         |
|   | ( |                        |   |                |   |                |   |         |
|   | d |                        |   |                |   |                |   |         |
|   | o |                        |   |                |   |                |   |         |
|   | w |                        |   |                |   |                |   |         |
|   | n |                        |   |                |   |                |   |         |
|   | w |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | l |                        |   |                |   |                |   |         |
|   | l |                        |   |                |   |                |   |         |
|   | i |                        |   |                |   |                |   |         |
|   | n |                        |   |                |   |                |   |         |
|   | g |                        |   |                |   |                |   |         |
|   | g |                        |   |                |   |                |   |         |
|   | l |                        |   |                |   |                |   |         |
|   | o |                        |   |                |   |                |   |         |
|   | b |                        |   |                |   |                |   |         |
|   | a |                        |   |                |   |                |   |         |
|   | l |                        |   |                |   |                |   |         |
|   | a |                        |   |                |   |                |   |         |
|   | n |                        |   |                |   |                |   |         |
|   | d |                        |   |                |   |                |   |         |
|   | d |                        |   |                |   |                |   |         |
|   | i |                        |   |                |   |                |   |         |
|   | f |                        |   |                |   |                |   |         |
|   | f |                        |   |                |   |                |   |         |
|   | u |                        |   |                |   |                |   |         |
|   | s |                        |   |                |   |                |   |         |
|   | e |                        |   |                |   |                |   |         |
|   | ) |                        |   |                |   |                |   |         |
+---+---+------------------------+---+----------------+---+----------------+---+---------+

Table 2d. Measurements made aboard the R/V Vodyanitskiy++

+---+------------------------+----------------+----------------+---------+
|   | Property measured      | Principal      | Institution    |         |
|   |                        | Investigator   |                |         |
+---+------------------------+----------------+----------------+---------+
| * |                        |                |                |         |
| A |                        |                |                |         |
| t |                        |                |                |         |
| m |                        |                |                |         |
| o |                        |                |                |         |
| s |                        |                |                |         |
| p |                        |                |                |         |
| h |                        |                |                |         |
| e |                        |                |                |         |
| r |                        |                |                |         |
| i |                        |                |                |         |
| c |                        |                |                |         |
| C |                        |                |                |         |
| h |                        |                |                |         |
| e |                        |                |                |         |
| m |                        |                |                |         |
| i |                        |                |                |         |
| c |                        |                |                |         |
| a |                        |                |                |         |
| l |                        |                |                |         |
| * |                        |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol ionic mass,    | P. Quinn       | PMEL NOAA      |         |
|   | coarse and fine        |                |                |         |
|   | fraction               |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol ionic mass,    | P. Quinn       | PMEL NOAA      |         |
|   | size segregated        |                |                |         |
|   | (Berner impactor)      |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol OC and EC,     | T. Bates       | PMEL NOAA      |         |
|   | coarse and fine        |                |                |         |
|   | fraction               |                |                |         |
+---+------------------------+----------------+----------------+---------+
| # |                        |                |                |         |
| # |                        |                |                |         |
|   |                        |                |                |         |
| A |                        |                |                |         |
| e |                        |                |                |         |
| r |                        |                |                |         |
| o |                        |                |                |         |
| s |                        |                |                |         |
| o |                        |                |                |         |
| l |                        |                |                |         |
|   |                        |                |                |         |
| P |                        |                |                |         |
| h |                        |                |                |         |
| y |                        |                |                |         |
| s |                        |                |                |         |
| i |                        |                |                |         |
| c |                        |                |                |         |
| a |                        |                |                |         |
| l |                        |                |                |         |
|   |                        |                |                |         |
| A |                        |                |                |         |
| n |                        |                |                |         |
| d |                        |                |                |         |
|   |                        |                |                |         |
| O |                        |                |                |         |
| p |                        |                |                |         |
| t |                        |                |                |         |
| i |                        |                |                |         |
| c |                        |                |                |         |
| a |                        |                |                |         |
| l |                        |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Particle number, Dp \> | T. Bates       | PMEL NOAA      |         |
|   | 15 nm                  |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol size           | T. Bates       | PMEL NOAA      |         |
|   | distribution           |                |                |         |
|   |                        |                |                |         |
|   | (Twin DMA+APS)         |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Hygroscopic growth     | B. Busch       | Institute for  |         |
|   | factors for Dp = 50 -  |                | Tropospheric   |         |
|   | 250 nm                 |                | Research       |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol total mass,    | P. Quinn       | PMEL NOAA      |         |
|   | coarse and fine        |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol scattering,    | P. Quinn       | PMEL NOAA      |         |
|   | backscattering, and    |                |                |         |
|   | backscattered fraction |                |                |         |
|   | at 3 wavelengths with  |                |                |         |
|   | Dp \< 1 µm             |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol scattering,    | P. Quinn       | PMEL NOAA      |         |
|   | backscattering         |                |                |         |
|   | coefficients at 3      |                |                |         |
|   | wavelengths with Dp \< |                |                |         |
|   | 10 µm                  |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol absorption,    | P. Quinn       | PMEL NOAA      |         |
|   | scattering, and single |                |                |         |
|   | scattering albedo at   |                |                |         |
|   | 550 nm.                |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol optical depth, | R. Frouin      | University of  |         |
|   | 4 wavelengths          |                | California at  |         |
|   |                        |                | San Diego      |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol optical depth, | P. Quinn       | PMEL NOAA      |         |
|   | 4 wavelengths          |                |                |         |
|   | (handheld              |                |                |         |
|   | sunphotometers)        |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol optical depth  | P. Russell     | NASA Ames      |         |
|   | at 5 wavelengths,      |                |                |         |
|   | water vapor column     |                |                |         |
|   | (AATS-6)               |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Lidar backscatter at   | V.             | University of  |         |
|   | 1064 nm                | Freudenthaler  | München        |         |
+---+------------------------+----------------+----------------+---------+

  -------------- ------------------------- ---------------- ----------------- ---------
                 Property measured         Principal        Institution       
                                           Investigator                       

  *Meteorology                                                                
  And Others*                                                                 

                 Radiosoundings            J. Johnson       PMEL NOAA         

                 Water-leaving radiance    R. Frouin        University of     
                                                            California at San 
                                                            Diego             
  -------------- ------------------------- ---------------- ----------------- ---------

++cf. (Johnson et al., 2000) for complete list

Table 2e. Measurements made at Punta del Hidalgo

  -------------- ------------------------- ---------------- ----------------- ---------
                 Property measured         Principal        Institution       
                                           Investigator                       

  *Atmospheric                                                                
  Chemistry*                                                                  

                 Aerosol ionic mass,       J. P. Putaud     Joint Research    
                 coarse and fine fraction                   Centre, Ispra     

                 Aerosol carbon mass, fine J. P. Putaud     Joint Research    
                 fraction                                   Centre, Ispra     

                 Aerosol ionic mass, size  A. Allen         University of     
                 segregated (MOUDI                          Birmingham        
                 impactor)                                                    

                 Aerosol ionic mass, size  H. Sievering     University of     
                 segregated (Sierra                         Colorado          
                 impactor)                                                    

                 Aerosol ionic mass,       N. Hewitt        University of     
                 coarse and fine fraction                   Lancaster         

                 Elemental aerosol         E. Swietlicki    University of     
                 concentration ratios of                    Lund              
                 H, C, N, O, K, Ca, V and                                     
                 Br to S (Dp \< 1 µm)                                         

  *Aerosol                                                                    
  Physical And                                                                
  Optical*                                                                    

                 Aerosol size              R. Van Dingenen  Joint Research    
                 distributions and                          Centre, Ispra     
                 integrated number,                                           
                 surface area and volume                                      
                 (DMA)                                                        

                 Aerosol size distribution E. Swietlicki    University of     
                 Dp \> 0.4 µm (TSI-APS)                     Lund              

                 Ratio of CCN (0.2 and     P. Aalto         University of     
                 0.5%) to CN at specific                    Helsinki          
                 dry sizes                                                    

                 Hygroscopic growth        E. Swietlicki    University of     
                 factors for Dp = 0.035 -                   Lund              
                 0.44 µm                                                      

                 Aerosol absorption        R. Van Dingenen  Joint Research    
                 coefficient - Equivalent                   Centre, Ispra     
                 Black Carbon                                                 
                 concentration                                                

                 Aerosol optical depth     B. Holben        NASA Goddard      
                 spectra and sky radiance                                     
                 (AERONET Cimel)                                              
  -------------- ------------------------- ---------------- ----------------- ---------

Table 2f. Measurements made at Santa Cruz de Tenerife, San Cristobal de
La Laguna, and Las Galletas

+---+----------------------------+---+------------------+---+------------------+---+
|   | Property measured          |   | Principal        | I |                  |   |
|   |                            |   | Investigator     | n |                  |   |
|   |                            |   |                  | s |                  |   |
|   |                            |   |                  | t |                  |   |
|   |                            |   |                  | i |                  |   |
|   |                            |   |                  | t |                  |   |
|   |                            |   |                  | u |                  |   |
|   |                            |   |                  | t |                  |   |
|   |                            |   |                  | i |                  |   |
|   |                            |   |                  | o |                  |   |
|   |                            |   |                  | n |                  |   |
+---+----------------------------+---+------------------+---+------------------+---+
| * |                            |   |                  |   |                  |   |
| A |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| r |                            |   |                  |   |                  |   |
| o |                            |   |                  |   |                  |   |
| s |                            |   |                  |   |                  |   |
| o |                            |   |                  |   |                  |   |
| l |                            |   |                  |   |                  |   |
| O |                            |   |                  |   |                  |   |
| p |                            |   |                  |   |                  |   |
| t |                            |   |                  |   |                  |   |
| i |                            |   |                  |   |                  |   |
| c |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| l |                            |   |                  |   |                  |   |
| M |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| s |                            |   |                  |   |                  |   |
| u |                            |   |                  |   |                  |   |
| r |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| m |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| n |                            |   |                  |   |                  |   |
| t |                            |   |                  |   |                  |   |
| s |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| t |                            |   |                  |   |                  |   |
| S |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| n |                            |   |                  |   |                  |   |
| t |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| C |                            |   |                  |   |                  |   |
| r |                            |   |                  |   |                  |   |
| u |                            |   |                  |   |                  |   |
| z |                            |   |                  |   |                  |   |
| D |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| T |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| n |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| r |                            |   |                  |   |                  |   |
| i |                            |   |                  |   |                  |   |
| f |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| * |                            |   |                  |   |                  |   |
+---+----------------------------+---+------------------+---+------------------+---+
|   | Aerosol optical depth      |   | J. P. Diaz       | U |                  |   |
|   | (AOD) from sun photometry  |   |                  | n |                  |   |
|   |                            |   |                  | i |                  |   |
|   |                            |   |                  | v |                  |   |
|   |                            |   |                  | e |                  |   |
|   |                            |   |                  | r |                  |   |
|   |                            |   |                  | s |                  |   |
|   |                            |   |                  | i |                  |   |
|   |                            |   |                  | t |                  |   |
|   |                            |   |                  | y |                  |   |
|   |                            |   |                  | o |                  |   |
|   |                            |   |                  | f |                  |   |
|   |                            |   |                  | L |                  |   |
|   |                            |   |                  | a |                  |   |
|   |                            |   |                  | L |                  |   |
|   |                            |   |                  | a |                  |   |
|   |                            |   |                  | g |                  |   |
|   |                            |   |                  | u |                  |   |
|   |                            |   |                  | n |                  |   |
|   |                            |   |                  | a |                  |   |
+---+----------------------------+---+------------------+---+------------------+---+
|   | Aerosol optical depth      |   | T. Elias         | L |                  |   |
|   | spectra and polarized sky  |   |                  | a |                  |   |
|   | radiance (LOA Cimel)       |   |                  | b |                  |   |
|   |                            |   |                  | o |                  |   |
|   |                            |   |                  | r |                  |   |
|   |                            |   |                  | a |                  |   |
|   |                            |   |                  | t |                  |   |
|   |                            |   |                  | o |                  |   |
|   |                            |   |                  | i |                  |   |
|   |                            |   |                  | r |                  |   |
|   |                            |   |                  | e |                  |   |
|   |                            |   |                  | d |                  |   |
|   |                            |   |                  | \ |                  |   |
|   |                            |   |                  | ' |                  |   |
|   |                            |   |                  | O |                  |   |
|   |                            |   |                  | p |                  |   |
|   |                            |   |                  | t |                  |   |
|   |                            |   |                  | i |                  |   |
|   |                            |   |                  | q |                  |   |
|   |                            |   |                  | u |                  |   |
|   |                            |   |                  | e |                  |   |
|   |                            |   |                  | A |                  |   |
|   |                            |   |                  | t |                  |   |
|   |                            |   |                  | m |                  |   |
|   |                            |   |                  | o |                  |   |
|   |                            |   |                  | s |                  |   |
|   |                            |   |                  | p |                  |   |
|   |                            |   |                  | h |                  |   |
|   |                            |   |                  | e |                  |   |
|   |                            |   |                  | r |                  |   |
|   |                            |   |                  | i |                  |   |
|   |                            |   |                  | q |                  |   |
|   |                            |   |                  | u |                  |   |
|   |                            |   |                  | e |                  |   |
|   |                            |   |                  | , |                  |   |
|   |                            |   |                  | V |                  |   |
|   |                            |   |                  | i |                  |   |
|   |                            |   |                  | l |                  |   |
|   |                            |   |                  | l |                  |   |
|   |                            |   |                  | e |                  |   |
|   |                            |   |                  | n |                  |   |
|   |                            |   |                  | e |                  |   |
|   |                            |   |                  | u |                  |   |
|   |                            |   |                  | v |                  |   |
|   |                            |   |                  | e |                  |   |
|   |                            |   |                  | d |                  |   |
|   |                            |   |                  | Á |                  |   |
|   |                            |   |                  | s |                  |   |
|   |                            |   |                  | c |                  |   |
|   |                            |   |                  | q |                  |   |
|   |                            |   |                  | , |                  |   |
|   |                            |   |                  | F |                  |   |
|   |                            |   |                  | r |                  |   |
|   |                            |   |                  | a |                  |   |
|   |                            |   |                  | n |                  |   |
|   |                            |   |                  | c |                  |   |
|   |                            |   |                  | e |                  |   |
+---+----------------------------+---+------------------+---+------------------+---+
| # |                            |   |                  |   |                  |   |
| # |                            |   |                  |   |                  |   |
| # |                            |   |                  |   |                  |   |
| # |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| A |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| r |                            |   |                  |   |                  |   |
| o |                            |   |                  |   |                  |   |
| s |                            |   |                  |   |                  |   |
| o |                            |   |                  |   |                  |   |
| l |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| O |                            |   |                  |   |                  |   |
| p |                            |   |                  |   |                  |   |
| t |                            |   |                  |   |                  |   |
| i |                            |   |                  |   |                  |   |
| c |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| l |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| M |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| s |                            |   |                  |   |                  |   |
| u |                            |   |                  |   |                  |   |
| r |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| m |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| n |                            |   |                  |   |                  |   |
| t |                            |   |                  |   |                  |   |
| s |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| A |                            |   |                  |   |                  |   |
| t |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| S |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| n |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| C |                            |   |                  |   |                  |   |
| r |                            |   |                  |   |                  |   |
| i |                            |   |                  |   |                  |   |
| s |                            |   |                  |   |                  |   |
| t |                            |   |                  |   |                  |   |
| o |                            |   |                  |   |                  |   |
| b |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| l |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| d |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| L |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| L |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| g |                            |   |                  |   |                  |   |
| u |                            |   |                  |   |                  |   |
| n |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
+---+----------------------------+---+------------------+---+------------------+---+
| # |                            | # |                  |   | ###              |   |
| # |                            | # |                  |   | # Laboratoire d\ |   |
| # |                            | # |                  |   | 'Optique Atmosph |   |
| # |                            | # |                  |   | erique, Villeneu |   |
|   |                            |   |                  |   | ve dÁscq, France |   |
| A |                            | T |                  |   |                  |   |
| e |                            | . |                  |   |                  |   |
| r |                            |   |                  |   |                  |   |
| o |                            | E |                  |   |                  |   |
| s |                            | l |                  |   |                  |   |
| o |                            | i |                  |   |                  |   |
| l |                            | a |                  |   |                  |   |
|   |                            | s |                  |   |                  |   |
| o |                            |   |                  |   |                  |   |
| p |                            |   |                  |   |                  |   |
| t |                            |   |                  |   |                  |   |
| i |                            |   |                  |   |                  |   |
| c |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| l |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| d |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| p |                            |   |                  |   |                  |   |
| t |                            |   |                  |   |                  |   |
| h |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| s |                            |   |                  |   |                  |   |
| p |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| c |                            |   |                  |   |                  |   |
| t |                            |   |                  |   |                  |   |
| r |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| n |                            |   |                  |   |                  |   |
| d |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| p |                            |   |                  |   |                  |   |
| o |                            |   |                  |   |                  |   |
| l |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| r |                            |   |                  |   |                  |   |
| i |                            |   |                  |   |                  |   |
| z |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| d |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| s |                            |   |                  |   |                  |   |
| k |                            |   |                  |   |                  |   |
| y |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| r |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| d |                            |   |                  |   |                  |   |
| i |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| n |                            |   |                  |   |                  |   |
| c |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| ( |                            |   |                  |   |                  |   |
| L |                            |   |                  |   |                  |   |
| O |                            |   |                  |   |                  |   |
| A |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| R |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| f |                            |   |                  |   |                  |   |
| P |                            |   |                  |   |                  |   |
| o |                            |   |                  |   |                  |   |
| l |                            |   |                  |   |                  |   |
| , |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| C |                            |   |                  |   |                  |   |
| i |                            |   |                  |   |                  |   |
| m |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| l |                            |   |                  |   |                  |   |
| ) |                            |   |                  |   |                  |   |
+---+----------------------------+---+------------------+---+------------------+---+
| # |                            |   |                  |   |                  |   |
| # |                            |   |                  |   |                  |   |
| # |                            |   |                  |   |                  |   |
| # |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| A |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| r |                            |   |                  |   |                  |   |
| o |                            |   |                  |   |                  |   |
| s |                            |   |                  |   |                  |   |
| o |                            |   |                  |   |                  |   |
| l |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| O |                            |   |                  |   |                  |   |
| p |                            |   |                  |   |                  |   |
| t |                            |   |                  |   |                  |   |
| i |                            |   |                  |   |                  |   |
| c |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| l |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| M |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| s |                            |   |                  |   |                  |   |
| u |                            |   |                  |   |                  |   |
| r |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| m |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| n |                            |   |                  |   |                  |   |
| t |                            |   |                  |   |                  |   |
| s |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| A |                            |   |                  |   |                  |   |
| t |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| L |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| s |                            |   |                  |   |                  |   |
|   |                            |   |                  |   |                  |   |
| G |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| l |                            |   |                  |   |                  |   |
| l |                            |   |                  |   |                  |   |
| e |                            |   |                  |   |                  |   |
| t |                            |   |                  |   |                  |   |
| a |                            |   |                  |   |                  |   |
| s |                            |   |                  |   |                  |   |
+---+----------------------------+---+------------------+---+------------------+---+
|   | Aerosol backscatter and    |   | J. Reagan        | U |                  |   |
|   | extinction (Micro-Pulse    |   |                  | n |                  |   |
|   | Lidar)                     |   |                  | i |                  |   |
|   |                            |   |                  | v |                  |   |
|   |                            |   |                  | e |                  |   |
|   |                            |   |                  | r |                  |   |
|   |                            |   |                  | s |                  |   |
|   |                            |   |                  | i |                  |   |
|   |                            |   |                  | t |                  |   |
|   |                            |   |                  | y |                  |   |
|   |                            |   |                  | o |                  |   |
|   |                            |   |                  | f |                  |   |
|   |                            |   |                  | A |                  |   |
|   |                            |   |                  | r |                  |   |
|   |                            |   |                  | i |                  |   |
|   |                            |   |                  | z |                  |   |
|   |                            |   |                  | o |                  |   |
|   |                            |   |                  | n |                  |   |
|   |                            |   |                  | a |                  |   |
+---+----------------------------+---+------------------+---+------------------+---+
|   | Aerosol optical depth from |   | J. Reagan        | U |                  |   |
|   | sun photometry at 10       |   |                  | n |                  |   |
|   | wavelengths                |   |                  | i |                  |   |
|   |                            |   |                  | v |                  |   |
|   |                            |   |                  | e |                  |   |
|   |                            |   |                  | r |                  |   |
|   |                            |   |                  | s |                  |   |
|   |                            |   |                  | i |                  |   |
|   |                            |   |                  | t |                  |   |
|   |                            |   |                  | y |                  |   |
|   |                            |   |                  | o |                  |   |
|   |                            |   |                  | f |                  |   |
|   |                            |   |                  | A |                  |   |
|   |                            |   |                  | r |                  |   |
|   |                            |   |                  | i |                  |   |
|   |                            |   |                  | z |                  |   |
|   |                            |   |                  | o |                  |   |
|   |                            |   |                  | n |                  |   |
|   |                            |   |                  | a |                  |   |
+---+----------------------------+---+------------------+---+------------------+---+

Table 2g. Measurements made at Izaña+

+---+------------------------+----------------+----------------+---------+
|   | Property measured      | Principal      | Institution    |         |
|   |                        | Investigator   |                |         |
+---+------------------------+----------------+----------------+---------+
| * |                        |                |                |         |
| A |                        |                |                |         |
| t |                        |                |                |         |
| m |                        |                |                |         |
| o |                        |                |                |         |
| s |                        |                |                |         |
| p |                        |                |                |         |
| h |                        |                |                |         |
| e |                        |                |                |         |
| r |                        |                |                |         |
| i |                        |                |                |         |
| c |                        |                |                |         |
| C |                        |                |                |         |
| h |                        |                |                |         |
| e |                        |                |                |         |
| m |                        |                |                |         |
| i |                        |                |                |         |
| c |                        |                |                |         |
| a |                        |                |                |         |
| l |                        |                |                |         |
| * |                        |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | SO2 (LC)               | J. P. Putaud   | Joint Research |         |
|   |                        |                | Centre, Ispra  |         |
+---+------------------------+----------------+----------------+---------+
|   | Elemental aerosol      | E. Swietlicki  | University of  |         |
|   | concentration of H, C, |                | Lund           |         |
|   | N, O, S, K, Ca, V and  |                |                |         |
|   | Br (Dp \< 1 µm)        |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Single particle        | R. Van Grieken | University of  |         |
|   | elemental composition  |                | Antwerp        |         |
|   | and size               |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol ionic mass,    | J. P. Putaud   | Joint Research |         |
|   | coarse and fine        |                | Centre, Ispra  |         |
|   | fraction               |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol carbon mass,   | J. P. Putaud   | Joint Research |         |
|   | fine fraction          |                | Centre, Ispra  |         |
+---+------------------------+----------------+----------------+---------+
| * |                        |                |                |         |
| A |                        |                |                |         |
| e |                        |                |                |         |
| r |                        |                |                |         |
| o |                        |                |                |         |
| s |                        |                |                |         |
| o |                        |                |                |         |
| l |                        |                |                |         |
| P |                        |                |                |         |
| h |                        |                |                |         |
| y |                        |                |                |         |
| s |                        |                |                |         |
| i |                        |                |                |         |
| c |                        |                |                |         |
| a |                        |                |                |         |
| l |                        |                |                |         |
| A |                        |                |                |         |
| n |                        |                |                |         |
| d |                        |                |                |         |
| O |                        |                |                |         |
| p |                        |                |                |         |
| t |                        |                |                |         |
| i |                        |                |                |         |
| c |                        |                |                |         |
| a |                        |                |                |         |
| l |                        |                |                |         |
| * |                        |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol sub-µm size    | R. Van         | Joint Research |         |
|   | distribution and       | Dingenen       | Centre, Ispra  |         |
|   | integrated number,     |                |                |         |
|   | surface area and       |                |                |         |
|   | volume (DMA)           |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Hygroscopic growth     | J. Mäkelä      | University of  |         |
|   | factors for Dp = 10    |                | Helsinki       |         |
|   | and 50 nm              |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Volatility shrink      | J. Mäkelä      | University of  |         |
|   | factor for Dp = 10 and |                | Helsinki       |         |
|   | 50 nm                  |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol backscatter    | J. Welton      | University of  |         |
|   | and extinction         |                | Miami          |         |
|   | profiles (Micropulse   | (H. Gordon)    |                |         |
|   | Lidar)                 |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol optical depth  | B. Holben      | NASA Goddard   |         |
|   | spectra and sky        |                |                |         |
|   | radiance (AERONET      |                |                |         |
|   | Cimel)                 |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol optical depth  | T. Elias       | Laboratoire    |         |
|   | spectra and polarized  |                | d\'Optique     |         |
|   | sky radiance (LOA      |                | Atmospherique, |         |
|   | Cimel, RefPol)         |                | Villeneuve     |         |
|   |                        |                | dÁscq, France  |         |
+---+------------------------+----------------+----------------+---------+

+Partial list

Table 2h. Measurements made at Teide

  ---------- ------------------------- ---------------- ----------------- ---------
             Property measured         Principal        Institution       
                                       Investigator                       

  *Aerosol                                                                
  Physical                                                                
  And                                                                     
  Optical*                                                                

             Aerosol optical depth     M. Andreae       Max Planck        
             spectra (YES shadow-band                   Institute for     
             radiometer)                                Chemistry, Mainz  

             Aerosol optical depth     M. Andreae       Max Planck        
             spectra and sky radiance                   Institute for     
             (AERONET Cimel)                            Chemistry, Mainz  
  ---------- ------------------------- ---------------- ----------------- ---------

Table 2i. Measurements made aboard the Pelican aircraft

+---+------------------------+----------------+----------------+---------+
|   | Property measured      | Principal      | Institution    |         |
|   |                        | Investigator   |                |         |
+---+------------------------+----------------+----------------+---------+
| # |                        |                |                |         |
| # |                        |                |                |         |
|   |                        |                |                |         |
| A |                        |                |                |         |
| e |                        |                |                |         |
| r |                        |                |                |         |
| o |                        |                |                |         |
| s |                        |                |                |         |
| o |                        |                |                |         |
| l |                        |                |                |         |
|   |                        |                |                |         |
| C |                        |                |                |         |
| h |                        |                |                |         |
| e |                        |                |                |         |
| m |                        |                |                |         |
| i |                        |                |                |         |
| c |                        |                |                |         |
| a |                        |                |                |         |
| l |                        |                |                |         |
|   |                        |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol ionic mass,    | L. Russell     | Princeton      |         |
|   | carbon, and trace      |                | University     |         |
|   | metals in fine         |                |                |         |
|   | fraction \< 2.5 µm     |                |                |         |
+---+------------------------+----------------+----------------+---------+
| # |                        |                |                |         |
| # |                        |                |                |         |
|   |                        |                |                |         |
| A |                        |                |                |         |
| e |                        |                |                |         |
| r |                        |                |                |         |
| o |                        |                |                |         |
| s |                        |                |                |         |
| o |                        |                |                |         |
| l |                        |                |                |         |
|   |                        |                |                |         |
| A |                        |                |                |         |
| n |                        |                |                |         |
| d |                        |                |                |         |
|   |                        |                |                |         |
| C |                        |                |                |         |
| l |                        |                |                |         |
| o |                        |                |                |         |
| u |                        |                |                |         |
| d |                        |                |                |         |
|   |                        |                |                |         |
| P |                        |                |                |         |
| h |                        |                |                |         |
| y |                        |                |                |         |
| s |                        |                |                |         |
| i |                        |                |                |         |
| c |                        |                |                |         |
| a |                        |                |                |         |
| l |                        |                |                |         |
|   |                        |                |                |         |
| A |                        |                |                |         |
| n |                        |                |                |         |
| d |                        |                |                |         |
|   |                        |                |                |         |
| O |                        |                |                |         |
| p |                        |                |                |         |
| t |                        |                |                |         |
| i |                        |                |                |         |
| c |                        |                |                |         |
| a |                        |                |                |         |
| l |                        |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Size distributions     | D. Collins (R. | California     |         |
|   | (DMA)                  | Flagan/ J.     | Institute of   |         |
|   |                        | Seinfeld)      | Technology     |         |
+---+------------------------+----------------+----------------+---------+
|   | Size distributions     | H. Jonsson     | California     |         |
|   | (PCASP,FSSP)           |                | Institute of   |         |
|   |                        |                | Technology     |         |
+---+------------------------+----------------+----------------+---------+
|   | CCN spectra (0.1%      | P. Chuang (R.  | California     |         |
|   | supersaturation)       | Flagan/J.      | Institute of   |         |
|   |                        | Seinfeld)      | Technology     |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol scattering and | K. Noone       | Stockholm      |         |
|   | absorption             |                | University     |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol scattering,    | S. Gassó       | University of  |         |
|   | wet and dry            |                | Washington     |         |
+---+------------------------+----------------+----------------+---------+
|   | Aerosol optical depth  | P. Russell     | NASA Ames      |         |
|   | at 13 wavelengths and  |                | Research       |         |
|   | water vapor column     |                | Center         |         |
|   | (AATS-14)              |                |                |         |
+---+------------------------+----------------+----------------+---------+
| * |                        |                |                |         |
| M |                        |                |                |         |
| e |                        |                |                |         |
| t |                        |                |                |         |
| e |                        |                |                |         |
| o |                        |                |                |         |
| r |                        |                |                |         |
| o |                        |                |                |         |
| l |                        |                |                |         |
| o |                        |                |                |         |
| g |                        |                |                |         |
| i |                        |                |                |         |
| c |                        |                |                |         |
| a |                        |                |                |         |
| l |                        |                |                |         |
| A |                        |                |                |         |
| n |                        |                |                |         |
| d |                        |                |                |         |
| O |                        |                |                |         |
| t |                        |                |                |         |
| h |                        |                |                |         |
| e |                        |                |                |         |
| r |                        |                |                |         |
| * |                        |                |                |         |
+---+------------------------+----------------+----------------+---------+
|   | Position, meteorology  | H. Jonsson     | CIRPAS         |         |
+---+------------------------+----------------+----------------+---------+
|   | Radiative fluxes       | H. Jonsson     | CIRPAS         |         |
+---+------------------------+----------------+----------------+---------+
|   | T, RH, pressure        | S. Gassó       | University of  |         |
|   |                        |                | Washington     |         |
+---+------------------------+----------------+----------------+---------+

Table 2j. Measurements made aboard C-414 aircraft

  ---------- ------------------------- ---------------- ----------------- ---------
             Property measured         Principal        Institution       
                                       Investigator                       

  *Aerosol                                                                
  Optical*                                                                

             Spectral upwelling        M. Silva         University of     
             radiances at 230m and                      Evora             
             520m height (0.45-0.52;                                      
             0.52-0.60; 0.60-0.63;                                        
             0.63-0.69; 0.70-0.75;                                        
             0.91-1.05um) by                                              
             spectralradiometer                                           
  ---------- ------------------------- ---------------- ----------------- ---------

Table 2k. Measurements aboard the C-130 aircraft++

  ----------------- ------------------------- ---------------- ----------------- ---------
                    Property measured         Principal        Institution       
                                              Investigator                       

  *Atmospheric                                                                   
  Chemical*                                                                      

                    Aerosol ionic mass,       A. Andreae       Max Planck        
                    coarse and fine fraction                   Institute for     
                                                               chemistry, Mainz  

  *Aerosol And                                                                   
  Cloud Physical                                                                 
  And Optical*                                                                   

                    Particles, Dp \> 3 nm     D. Johnson       Meteorological    
                    (TSI 3025)                                 Research Flight,  
                                                               Farnborough       

                    Particles, Dp \> 100 nm   D. Johnson       Meteorological    
                    (PCASP)                                    Research Flight,  
                                                               Farnborough       

                    Particles, Dp \> 500 nm   D. Johnson       Meteorological    
                    (FSSP)                                     Research Flight,  
                                                               Farnborough       

                    Heated/Ambient aerosol    C. O\'Dowd       U. Sunderland     
                    size distributions                                           
                    (VACC/SMPS)                                                  

                    Aerosol scattering and    D. Johnson       Meteorological    
                    absorption                                 Research Flight,  
                                                               Farnborough       

                    CCN spectra               D. Johnson       Meteorological    
                                                               Research Flight,  
                                                               Farnborough       

  *Meteorological                                                                
  And Others*                                                                    

                    Broad Band Radiometers    D. Johnson       Meteorological    
                                                               Research Flight,  
                                                               Farnborough       
  ----------------- ------------------------- ---------------- ----------------- ---------

++See LAGRANGIAN overview paper (Johnson et al., 2000) for complete list

Table 2l. Measurements aboard the ARAT aircraft+++

  -------------- ------------------------- ---------------- ----------------- ---------
                 Property measured         Principal        Institution       
                                           Investigator                       

  *Aerosol &                                                                  
  Cloud Physical                                                              
  And Optical*                                                                

                 Particles \> 300 nm (PMS  J. Pelon         Institut National 
                 ASASP)                                     des Sciences de   
                                                            l\'Univers, Paris 

                 Aerosol extinction        J. Pelon         Institut National 
                 coefficient from airborne                  des Sciences de   
                 lidar LEANDRE                              l\'Univers, Paris 

  *Meteorology                                                                
  And Others*                                                                 

                 Position, winds,          J. Pelon         Institut National 
                 thermodynamics,                            des Sciences de   
                 radiation, etc.                            l\'Univers, Paris 
  -------------- ------------------------- ---------------- ----------------- ---------

+++See CLOUDYCOLUMN overview paper (Brenguier et al., 2000) for complete
list

Table 2m. Measurements made on satellites

+---+-----------------------------+------------------+-------------------+
|   | Property measured           | Principal        | Institution       |
|   |                             | Investigator     |                   |
+---+-----------------------------+------------------+-------------------+
|   | METEOSAT images 6-hourly,   | M. Van           | Joint Research    |
|   | VIS, IR and WV (GIF)        | Liedekerke       | Centre, Ispra     |
+---+-----------------------------+------------------+-------------------+
|   | METEOSAT full data; VIS, IR | M. Van           | Joint Research    |
|   | and WV channels             | Liedekerke       | Centre, Ispra     |
+---+-----------------------------+------------------+-------------------+
|   | Aerosol optical depth and   | F. Exposito      | University of La  |
|   | ratio Ch1/Ch2               |                  | Laguna, Tenerife  |
|   | (NOAA14-AVHRR, GIF)         |                  |                   |
+---+-----------------------------+------------------+-------------------+
|   | Aerosol optical depth,      | G. de Leeuw      | TNO-FEL, the      |
|   |                             |                  | Hague,            |
|   | ERS-2/ATSR                  |                  |                   |
|   |                             |                  | Netherlands       |
+---+-----------------------------+------------------+-------------------+
|   | Aerosol optical depth at    | P. Durkee        | Naval             |
|   | 630, 860 nm (NOAA-12, -14   |                  | Postgraduate      |
|   | AVHRR; METEOSAT imager)     |                  | School, Monterey, |
|   |                             |                  | CA                |
+---+-----------------------------+------------------+-------------------+
|   | Aerosol optical depth,      | D. Tanré         | Laboratoire       |
|   | ADEOS/POLDER                |                  | d\'Optique        |
|   |                             |                  | Atmospherique,    |
|   |                             |                  | Villeneuve dÁscq, |
|   |                             |                  | France            |
+---+-----------------------------+------------------+-------------------+
|   | Aerosol optical depth,      | T. Nakajima      | University of     |
|   | ADEOS/OCTS                  |                  | Tokyo             |
+---+-----------------------------+------------------+-------------------+

> Table 3. Periods initially chosen for CLEARCOLUMN data evaluation in
> the Sagres area. Julian day is defined here such that noon on February
> 1 equals Julian day 31.5.

+--------+------------+------------+--------+------+---------+------+
| Chosen | start      | end        | start  | time | end     | time |
| Day    |            |            |        |      |         |      |
|        | Julian day | Julian day | date   | GMT  | date    | GMT  |
+--------+------------+------------+--------+------+---------+------+
| 1      | 166.8      | 167.8      | 970616 | 1    | 970617  | 1    |
|        |            |            |        | 9:12 |         | 9:12 |
+--------+------------+------------+--------+------+---------+------+
| 2      | 170.8      | 171.4      | 970620 | 1    | 970622  | 9:36 |
|        |            |            |        | 9:12 |         |      |
+--------+------------+------------+--------+------+---------+------+
| 3      | 172        | 172.25     | 970622 | 0:00 | 970622  | 6:00 |
+--------+------------+------------+--------+------+---------+------+
| 4      | 174        | 174.3      | 970624 | 0:00 | 970624  | 7:12 |
+--------+------------+------------+--------+------+---------+------+
| 5      | 177.8      | 179.8      | 970627 | 1    | 970629  | 1    |
|        |            |            |        | 9:12 |         | 9:12 |
+--------+------------+------------+--------+------+---------+------+
| 6      | 180.5      | 181.2      | 970630 | 1    | 970701  | 4:48 |
|        |            |            |        | 2:00 |         |      |
+--------+------------+------------+--------+------+---------+------+
| 7      | 182.5      | 184        | 970702 | 1    | 970704  | 0:00 |
|        |            |            |        | 2:00 |         |      |
+--------+------------+------------+--------+------+---------+------+
| 8      | 188        | 189.3      | 970807 | 0:00 | 970709  | 7:12 |
+--------+------------+------------+--------+------+---------+------+
| 9      | 189.8      | 190.3      | 970907 | 1    | 970710  | 7:12 |
|        |            |            |        | 9:12 |         |      |
+--------+------------+------------+--------+------+---------+------+
| 10     | 190.3      | 190.9      | 971007 | 7:12 | 970710  | 2    |
|        |            |            |        |      |         | 1:36 |
+--------+------------+------------+--------+------+---------+------+
| 11     | 193.5      | 194.8      | 970713 | 1    | 970714  | 1    |
|        |            |            |        | 2:00 |         | 9:12 |
+--------+------------+------------+--------+------+---------+------+
| 12     | 197.5      | 198.5      | 970717 | 1    | 970718  | 1    |
|        |            |            |        | 2:00 |         | 2:00 |
+--------+------------+------------+--------+------+---------+------+
| 13     | 201.5      | 202.3      | 970721 | 1    | 970722  | 7:12 |
|        |            |            |        | 2:00 |         |      |
+--------+------------+------------+--------+------+---------+------+
| 14     | 202.3      | 202.75     | 970722 | 7:12 | 970722  | 1    |
|        |            |            |        |      |         | 8:00 |
+--------+------------+------------+--------+------+---------+------+
| 15     | 203        | 203.65     | 970723 | 0:00 | 970723  | 1    |
|        |            |            |        |      |         | 5:36 |
+--------+------------+------------+--------+------+---------+------+

Figure Captions

1.  Schematic overview of CLEARCOLUMN sites and platforms.

2\. Flow chart of the evaluation methodology of CLEARCOLUMN. Squares
mark input data. Ovals stand for processing steps and rounded rectangles
indicate deliverables.

![](media/image1.pct){width="5.222222222222222in"
height="3.263888888888889in"}

Fig. 1. Schematic overview of CLEARCOLUMN sites and platforms.

![](media/image2.pct){width="6.013888888888889in"
height="6.819444444444445in"}

Fig. 2 Flow chart of the evaluation methodology of CLEARCOLUMN. Squares
mark input data. Ovals stand for processing steps and rounded rectangles
indicate deliverables.