![](media/image1.pct){width="5.833333333333333in"
height="4.402777777777778in"}

**Figure 2.** Sunphotometer channel wavelengths (vertical lines with
arrows) in relation to atmospheric spectra. The spectra of ln(1/T) were
calculated for the transmission T of the direct solar beam at sea level
using MODTRAN-3/Version 1.2 with a US Standard atmosphere, a
spring-summer tropospheric aerosol model, and the sun at the zenith.
Current center wavelengths of channel filters are 380.3, 448.3, 453.0,
499.4, 524.7, 605.4, 666.8, 711.8, 778.6, 864.4, 939.5,1018.7, 1059.0,
1557.5 nm for AATS-14 and 380.1, 450.7, 525.3, 863.9, 941.4, 1020.7 nm
for AATS-6. Filter full widths at half-maximum (FWHM) are 5 nm, except
for the 448, 453, and 1558 nm channels, which have FWHM 0.94, 2.17, and
30 nm, respectively.

![](media/image2.pct){width="4.059722222222222in"
height="6.0465277777777775in"}

**Figure 3.** Latitude transects of aerosol optical depth and Ångström
wavelength exponent as derived from the AATS-6 sunphotometer aboard the
UW C-131A, the ATSR-2, and the AVHRR. (a) AVHRR retrieved aerosol
optical depth for channel 1 (0.64 µm) and sunphotometer derived aerosol
optical depth at 0.64 µm. (b) same as (a) but for ATSR-2 retrieved
aerosol optical depth at 0.525 µm and sunphotometer derived aerosol
optical depth at this wavelength; (c) Ångström wavelength exponent as
derived from AVHRR and from sunphotometer data; (d) same as (c) but for
Ångström wavelength exponent as derived from ATSR-2 and from
sunphotometer data (Veefkind et al., 1999).

![](media/image3.pct){width="5.513888888888889in"
height="3.8069444444444445in"}![](media/image4.pct){width="5.513888888888889in"
height="4.041666666666667in"}

**Figure 4.** Aerosol optical thickness measured by sunphotometer
(AATS-6) aboard the C-131A aircraft and derived from MAS data as a
function of wavelength. Top frame: Comparison at 37.49°N/74.16°W around
1830UTC. Bottom frame: The sunphotometer data were acquired over point
at 38.20°N/73.98°W at 1842UTC. The optical thicknesses derived from the
MAS are averaged over a geographical area defined by points located at
38.17°N/74.0°W and 38.27°N/74.1°W; the time of the acquisition was
around 1830UTC (Tanre et al., 1999).

![](media/image5.pct){width="6.3590277777777775in" height="7.225in"}

**Figure 5**. (a) Scatter diagram of aerosol optical depth retrieved
from AVHRR on the NOAA-14 satellite versus that measured by various
photometers at the surface (Durkee et al., 2000). (b) Comparison of
aerosol optical depth spectra measured in ACE-2 by AATS-14 on the
Pelican aircraft and AVHRR on the NOAA-14 Satellite, July 17, 1997.
(Livingston et al., 2000; Schmid et al., 2000). (c) As in (b), for
AATS-6 on the R/V Vodyanitskiy ship, AATS-14 on the Pelican aircraft,
and AVHRR on the NOAA-14 Satellite, July 10, 1997.

![](media/image6.pct){width="5.997222222222222in"
height="7.738888888888889in"}

**Figure 6**. Left panel: Profiles of aerosol optical depth at four
selected AATS-14 wavelengths (380, 500, 864 and 1558 nm) measured in
ACE-2 south of the coast of Tenerife. Right panel: Aerosol extinction
profiles derived by differentiating the profiles in the left panel.
(Schmid et al., 2000b)

![](media/image7.pct){width="5.997916666666667in"
height="4.4in"}**Figure 7**. Comparison of aerosol optical depth spectra
for the marine boundary layer (31-1111 m) during Pelican flight tf20 in
ACE 2 on July 8, 1997 (Schmid et al., 2000).

![](media/image7.pct){width="5.997916666666667in" height="4.50625in"}

**Figure 8**. Comparison of marine boundary layer aerosol size
distributions from in situ measurements and inverted from AATS-14
extinction spectra measured on Pelican flight tf15 in ACE 2 on July 17,
1997. Dashed lines indicate uncertainty of the in situ results (Schmid
et al., 2000).

![](media/image8.pct){width="5.999305555555556in"
height="4.963888888888889in"}

**Figure 9**. Left panel: Profile of the columnar water vapor above the
Pelican aircraft measured in ACE-2 south of the coast of Tenerife. Right
panel: Water vapor density derived by differentiating the profile in the
left panel. Also shown for comparison is the profile obtained by
combining readings of a humidograph and outside temperature on Pelican
(humidograph data courtesy of S. Gasso, University of Washington).
(Schmid et al., 2000)

![](media/image7.pct){width="7.495833333333334in"
height="5.634722222222222in"}

**Figure 10**. Scatter diagram of columnar water vapor calculated from
radiosonde measurements and from AATS-6 measurements during ACE-2. Each
AATS-6 data point represents the mean calculated over the time period
spanned by the radiosonde measurements; horizontal bars show the
corresponding standard deviation (wide ticks) and the range (narrow
ticks) for that time period (Livingston et al., 2000).

![](media/image9.pct){width="6.5in" height="4.555555555555555in"}

**Figure 11**. Aerosol single-scattering albedo profiles determined for
TARFOX flight 1728 (July 17, 1996) by two techniques. [Solid
line]{.underline}: derived by Redemann et al. (2000b) using *in situ*
particle size distributions and aerosol layer complex refractive index
estimates from Redemann et al. (2000a) that produce best agreement among
profiles of lidar backscatter, sunphotometer extinction, and relative
size distribution. Values were used in the first band of the Fu-Liou
radiative transfer model (0.2 µm \< \< 0.7 µm). [Dashed
line]{.underline}: derived by Hartley et al. (2000) at 450 nm by
combining in situ scattering, absorption, and size distribution
measurements. The gray-shaded area represents their uncertainty
estimates based on one standard deviation plus instrumental error.

![](media/image10.pct){width="7.135416666666667in" height="6.0in"}

**Figure 12**. Comparison between aerosol-induced change in downwelling
solar flux derived from C-130 pyranometer measurements (data points) and
calculated (curves) for size distributions retrieved from sunphotometer
optical depth spectra using an aqueous sulfate real refractive index and
a range of imaginary indexes to give the (550) values shown. The error
bar (cross) shows the uncertainty in flux change and broadband visible
optical depth determined from the C-130 pyranometer measurements
(Russell, et al., 1999b).