noaa / NATIONAL OCEANIC AND

ATMOSPHERIC ADMINISTRATION

Office of Oceanic and 

Atmospheric Research

NOAA Technical Memorandum OAR PSD-314

SUMMARY OF METEOROLOGICAL CONDITIONS DURING THE ARCTIC

MECHANISMS FOR THE INTERACTION OF THE SURFACE AND ATMOSPHERE

(AMISA) INTENSIVE OBSERVATION PERIODS

P.O.G. Persson

Earth System Research Laboratory

Physical Sciences Division

Boulder, Colorado

February 2010

UNITED STATES

DEPARTMENT OF COMMERCE

Gary Locke

Secretary

NATIONAL OCEANIC AND

ATMOSPHERIC ADMINISTRATION

Dr. Jane Lubchenco

Under Secretary for Oceans

and Atmosphere/Administrator

Office of Oceanic and 

Atmospheric Research

Dr. Richard Spinrad

Assistant Administrator

NOAA Technical Memorandum OAR PSD-314

SUMMARY OF METEOROLOGICAL CONDITIONS DURING THE ARCTIC

MECHANISMS FOR THE INTERACTION OF THE SURFACE AND ATMOSPHERE

(AMISA) INTENSIVE OBSERVATION PERIODS

P. Ola G. Persson

Cooperative Institute for Research in the Environmental Sciences (CIRES)

NOAA Earth System Research Laboratory/Physical Sciences Division

325 Broadway, Boulder, CO 80305

Earth System Research Laboratory

Physical Sciences Division

Boulder, Colorado

February 2010
ii 

NOTICE 

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NOAA/Earth System Research Laboratory. Use of information from this publication concerning 

proprietary products or the test of such products for publicity or advertising purposes is not 

authorized. 

______________________________________________________ 

For sale by the National Technical Information Service, 5285 Port Royal Road 

Springfield, VA 22061
iii 

Contents 

1. Introduction......................................................................................... 1 

2. AMISA and ASCOS Instrumentation.........................................................3 

3. General Meteorological Conditions............................................................7 

4. AMISA Intensive Observation Periods.......................................................11 

4.1 Transit Flight; Aug. 8, 2008 (YD221)........................................................11 

4.2 IOP 1; Aug. 12-13, 2008 (YD225-226)......................................................19 

4.3 IOP 2; Aug. 15, 2008 (YD228)................................................................27 

4.4 IOP 3; Aug. 22, 2008 (YD235)................................................................35 

4.5 IOP 4; Aug. 23, 2008 (YD236)................................................................41 

4.6 IOP 5; Aug. 25, 2008 (YD238)................................................................47 

5. AMISA Summary and Science Issues.........................................................55 

6. References...........................................................................................57 
AMISA

Arctic Mechanisms of

Interaction between the

Surface and Atmosphere

Kiruna, Sweden · 2008

CU Boulder · NOAA/ESRL

NASA Dryden·Goddard·Langley

Stockholm University

University of Leeds

NSERC
1 

1. Introduction 

The Arctic Mechanisms for the Interaction of the Surface and Atmosphere (AMISA) field 

program utilized the NASA DC-8 research aircraft, based in Kiruna, Sweden, to obtain data over 

the Arctic pack ice during August 2008. The program was conducted jointly with the Arctic 

Summer Cloud-Ocean Study (ASCOS), which consisted of the deployment of the Swedish 

icebreaker Oden north of Svalbard from Aug. 1 to Sep. 9. The Oden drifted with the pack ice 

near 87.5N, 5W between Aug. 12 (YD225) and Sep. 2 (YD246) (Fig. 1.1). Five research 

missions and two transit flights were flown with the DC-8 (Table 1.1) between Aug. 8 and Aug. 

26. Of the 5 research missions, 4 were focused on collecting data in the vicinity of the Oden and 

one focused on collecting data near the ice edge in Fram Strait between Svalbard and Greenland. 

The transit flight from California to Sweden included a flyover of the Oden and some data 

collection in its vicinity. The transit flight back to the United States went across Greenland and 

included some radiometric measurements of a glacier on the west side of southern Greenland, 

and is not discussed further here. The location of the aircraft base and its range allowed 

approximately 4 hours of on-station time for the aircraft in the immediate vicinity of the Oden 

(Fig. 1.1). The on-station time in Table 1.1 includes the times for the first and last dropsondes; 

i.e., the time of mission-objective data collection from the aircraft. 

The meteorological conditions of the first transit flight and five research missions are 

described here. The descriptions include a summary of the model forecasts for the mission, 

satellite images, some data from the aircraft, and some basic rawinsonde and remote sensing data 

Figure 1.1: ASCOS/AMISA Research Area Aug. 1 - Sep. 12, 2008. The white area shows sea ice extent on Sep. 3, 

2007. The magenta line shows median sea ice extent 1979-2000 (National Snow and Ice Data Center). 
2 

Table 1.1: List of AMISA DC8 science flight missions 

IOP Type Date Time (UTC) Cp (m/s) Sondes 

Transit Oden overpass Aug 8 

(YD221) 

0003-1215 

OS 0700-0840 

10.5/ 341° 5 

1 mapping, radiation, microphysics near 

Oden 

Aug 12-13 

(YD225-226) 

1802-0346, 

OS 2000-0130 

14.5/ 81 7 

2 mapping, radiation, microphysics, 

trajectory near Oden 

Aug. 15 

(YD228) 

0402-1510, 

OS 0500-1230 

13.9/175(all)

12.4/161(north)

4 

3 ice edge mapping, AMSR-E Aug. 22 

(YD235) 

0358-1210, 

OS 0530-1045 

10.3/191 3 

4 mapping, radiation, microphysics, 

trajectory near Oden 

Aug. 23 

(YD236) 

1204-2045, 

OS 1400-1830 

10.0/165 10 

5 mapping, radiation, microphysics, 

stratocumulus near Oden 

Aug. 25 

(YD238) 

0851-1923, 

OS 1100-1730 

15.8/254(upper)

5.0/290(lower) 

9 

from the Oden. Satellite-based estimates of system or cloud phase velocities valid during the onstation time are also presented. All times are given in Greenwich Mean Time (UTC), as this was 

the time used by the Oden. 

This report will first present a brief summary of the instrumentation on the DC-8 aircraft 

during AMISA and of the ASCOS instrumentation, followed by a section describing the general 

meteorological conditions during the ASCOS/AMISA field program. The fourth section, 

divided into six sub-sections, describes the meteorological environmental context of each 

research flight (or intensive observation period – IOP) and provides sample analyses. Data from 

the NASA DC-8, from the Oden, or from various meteorological services will be used to provide 

this meteorological context. The last section summarizes the accomplishments of AMISA and 

provides a synopsis of suggested scientific analyses possible from the various IOPs. Hence, this 

report provides a meteorological overview of the AMISA field program and the meteorological 

background of the individual flights necessary for researchers addressing the specific AMISA 

research objectives. Descriptive flight summaries produced by the NASA flight crew are 

available at http://www.nasa.gov/centers/dryden/home/AMISA_mission_science_report.html. 
3 

2. AMISA and ASCOS Instrumentation 

Because this summary of meteorological conditions will utilize data from the various 

instrument groups on board the DC-8, a brief summary of these instruments will be presented 

here. An extensive suite of radiometers was installed on the DC-8 aircraft (Fig. 2.1 and Table 

2.1). This included a scanning nadir-facing PSR/A imaging radiometer, a C-band radiometer, a 

Figure 2.1: The six basic instrument groups on the NASA DC-8 research aircraft during AMISA. 

temperature profiling radiometer, and a L-band salinity radiometer. Two radiometers had both a 

zenith and a nadir facing pair. These were dual-channel integrated water vapor and cloud liquid 

water radiometers and broadband shortwave and longwave radiometers. Dropsondes developed 

in conjunction with Yankee Environmental Systems were dropped from a chute in the rear of the 

aircraft. The Clark probe mounted on the right side of the fuselage allowed direct sampling of 

aerosol particles by the Volatile Aerosol Concentration and Composition (VACC) system, 

operated by the University of Leeds, and by the Langley Aerosol Research Group Experiment 

(LARGE). A Cloud, Aerosol, and Precipitation Spectrometer (CAPS) probe was mounted near 

the tip of the right wing of the aircraft. This probe also included a hot-wire cloud liquid water 

probe. 

During ASCOS, the atmosphere near and above the Oden was sampled by a suite of 

surface-based remote sensors and in-situ sensors providing information on the atmospheric 

thermodynamic, kinematic, and turbulent structure. These sensors included a 5-mm (60 GHz) 

scanning radiometer providing temperature profiles up to 1 km at time resolutions of 1 s to 10 

minutes; a 449 MHz wind profiler providing profiles of wind speed, wind direction, and 

turbulence intensity to about 6 km every 6-30 minutes; a Doppler S-band cloud and precipitation 

radar providing cloud macrophysical structure, fall velocity, and spectral width in both clouds 
4 

Table 2.1: List of instruments mounted on the NASA DC-8 aircraft during AMISA. 

Instrument Description Observables

Polarimetric Scanning 

Radiometer (PSR) 

Multiband polarimteric 

radiometric imaging system; 

Airborne AMSR-E equivalent;

10, 18, 21, 37, and 89 GHz 

high resolution sea ice mapping; 

cloud cover; integrated water vapor 

Dual-channel 

radiometer (DCR) 

21/31 GHz, up/downlooking integrated water vapor & cloud 

liquid water above/below aircraft 

Temperature profiling 

radiometer 

50-57 GHz, downlooking Profiles of air temperature 

Scanning Low 

Frequency Microwave 

Radiometer (SLFMR) 

L-band salinity mapping L-band brightness; mapped salinity 

with ~5 ppt precision for 

lead/meltpond discrimination 

Cloud, aerosol, and 

precipitation 

spectrometer (CAPS) 

From Droplet Measurements 

Technology 

Cloud droplet and ice particle 

spectra, liquid water content, 

droplet/ice discrimination 

Expendable digital 

dropsondes 

Yankee Technology Sub-aircraft profiles of temperature, 

pressure, humidity, and wind 

OAT Rosemount probe Outside air temperature 

adjusted for Mach number 

Air temperature 

pyranometers and 

pyrgeometers 

Hemispheric integrating 

thermopile irradiance sensors 

Up- and downwelling shortwave 

and longwave radiative fluxes 

DMT Cloud Aerosol 

and Precipitation 

Spectrometer (CAPS) 

– three probes 

cloud (optical array) imaging 

probe (CIP), 

cloud aerosol spectrometer 

(CAS), 

hot-wire sensor (LWC-100) 

cloud particle images and sizes (25 

m – 1.55 mm, 25 m resolution) 

particle size distribution (0.6 m – 

50 m) 

liquid water content (0.01- 3.0 g m-3)

Volatile Aerosol 

Concentration and 

Composition (VACC) 

University of Leeds' system Aerosol number concentration 

spectra and aerosol composition 

and precipitation to 10 km; a 8 mm (Ka-band) cloud radar providing cloud reflectivity, vertical 

velocity, and spectral information to 10 km at 45 m resolution, a dual-channel radiometer (23.8 

and 31.4 mm), a ceilometer, and a Scintec phased array sodar. The sodar provides turbulence 

and winds to about 600 m. Other remote sensors deployed during ASCOS included a vertically 

pointing depolarization mini-lidar providing backscatter and phase-partitioning up to significant 

cloud water regions, and a scanning Marine-Atmosphere Emitted Radiance Interferometer (MAERI) providing radiometric spectra from both the surface and the atmosphere. Other than the 

sodar, the remote sensors were located on the Oden (Fig. 2.2). 

In-situ profiling data at ASCOS are provided by 4X daily rawinsondes and 210 hours of 

basic meteorology parameters, turbulence, and aerosol spectra data (56% of deployment period 

from 8/17 – 9/1) from a tethersonde system deployed up to heights of about 700 m. Other than 

the 4X daily rawinsondes, the profiling observations have a temporal resolution of ~1 min to 1 

hour. Time-height data of temperature, wind, cloud outlines, turbulence, and derived parameters 

(e.g., Richardson number) are combined from the different sensors and examined for basic 
5 

boundary-layer structures and transition events. In addition, profiles of surface-layer 

temperature, humidity, wind, and turbulent fluxes were obtained from two towers (20-m and 30-

m) located on the ice near the Oden. Surface measurements of downwelling and upwelling 

shortwave and longwave radiative fluxes were also made, and solar radiometric flux 

measurements were also made beneath the ice on the floe near the Oden. 

More information on the instrument systems and access to the ASCOS and AMISA data 

are available from both at http://www.ascos.se/. Only basic meteorological parameters from the 

in-situ aircraft sampling system and the airborne aerosol data are currently available at the 

ASCOS site. Data from the CAPS microphysics probe, the dropsondes, or the suite of airborne 

radiation sensors can be requested by contacting Dr. Ola Persson (opersson@cires.colorado.edu) 

or Prof. Albin Gasiewski (Al.Gasiewski@colorado.edu). 

Combining the airborne and ice-breaker based observations allows the examination of 

many structures and processes associated with the clouds, the Arctic boundary-layer, and the ice 

surface during ASCOS/AMISA. In this report, the basic in-situ and dropsonde measurements 

from the NASA DC-8 will be combined with some of the surface-based observations to provide 

an understanding of the synoptic and mesoscale atmospheric structure sampled by the aircraft 

during the AMISA IOPs. 

Figure 2.2: Location of many of the remote sensors on the Oden during ASCOS/AMISA. 

7 

3. General Meteorological Conditions 

During the first two-thirds of the ASCOS field program (Aug. 3-24; YD216-237), 

synoptic storms were frequent. These storms are typically marked by warm air above the main 

Arctic inversion near 0.5-2 km, the presence of deep humidity and clouds (Fig. 3.1), and lower 

surface pressure. The strongest in this series of storms occurred on YD226-228 (Fig. 3.1d), 

which were sampled by IOPs 1 and 2. From Aug. 25-Sep. 3 (YD238-YD247), the weather at the 

Oden was marked by drier air above 1 km, colder air and persistent stratocumulus clouds in the 

lowest 2 kms, and higher surface pressure. Because the AMISA field program ended on Aug. 26 

(YD239), the first 5 flights were flown during the period with active synoptic storms. IOP4 

sampled the storm ending the cold snap period. Only the last flight, flown on YD238, sampled 

the drier, colder freeze-up period dominated by stratocumulus clouds, though stratocumulus 

clouds were sampled in all of the other IOPs over the Oden with the exception of the transit 

flight. 

One of the important goals of AMISA was to sample the atmosphere and surface before 

and after the onset of freeze-up. This transition can be measured in several ways. One way is to 

use 7- or 14-day running medians of the near-surface air temperature (Ta) and different threshold 

temperatures. Using the data from the Oden's meteorological station, the end of the melt season 

occurred on YD 220 (Aug. 7), YD 229 (Aug. 16), or YD 234 (Aug 21) (Fig. 3.1c). If the 

criterion of Martin and Munoz (1997) is used (T2, 14d_med < -0.1° C), AMISA failed to sample the 

end of the melt season and the Oden failed to establish its drifting station before the freezeup. 

However, with any of the other three criteria [Rigor et al. (2000), T2, 14d_med < -1° C; Andreas and 

Ackley (1982), T2, 14d_med < -1.9° C; Persson and Solomon (2008), T2, 7d_med < -1.8° C] , the 

transit flight and IOPs 1 and 2 occurred before the onset of the freeze-up, while IOPs 4 and 5 

occurred after the onset. In addition, preliminary analysis of on-ice surface energy flux 

observations was used to characterize ASCOS period into a melt, cold snap, and freeze-up 

periods. This characterization agrees with the end-of-melt criteria of PS08 and AA82. Hence, 

AMISA was successful in achieving its sampling goal. 

Photographs of the ice surface near the Oden during IOPs 1 & 2 (Fig. 3.2) show clearly 

discernible melt ponds and leads that have some grease ice. During IOPs 4 and 5, the meltponds 

are more frozen over and covered by snow, especially during IOP5. For instance, most of the 

meltponds near the Oden are no longer discernible on Aug. 25. The leads are still discernible, 

though they have larger areas of grease ice. 

The more gradual nature of the freeze-up transition, in contrast to the onset of melt, is 

evident in the broad temporal scatter of the freeze-up date from the different criteria and the 

series of photographs in Fig. 3.2. While the AMISA field program may have succeeded in 

obtaining missions on both sides of the freeze-up date using three of the criteria, more distinct 

contrasts between the melt season and the freeze-up period would likely have been obtained with 

an earlier start date and a later end date to the field program. 
8 

 

 

Figure 3.1: Top panels (a,b): Time-height series of temperature and relative humidity wrt ice from the 145 Oden 

rawinsondes (red stars along abscissa). The white frames show the six DC8 research flights, while the vertical 

green bars demark the 21-day Oden ice drift period. In a), the 0 C isopleths are bold. Bottom panels(c,d):Surface 

air temperature and pressure from the meteorological station at 35 m on the Oden. The vertical black lines on the 

temperature plot show the end of the melt season according to the temperature criteria of Martin and Munoz (1997; 

MM97), Rigor et al (2000;RCM00), Persson and Solomon (2008;PS08), and Andreas and Ackley (1982; AA82). The 

melt period, cold snap, and freeze-up periods are delineated by the vertical blue dashed lines. 
9 

Figure 3.2: Photographs of the ice surface near the Oden during a) IOP1, b) IOP2, c) IOP4, and d) IOP5. 

11 

4. AMISA Intensive Observation Periods 

4.1 Transit Flight; Aug. 8 (YD221)

Aircraft Takeoff: 00:03:07 Landing:~1215 On Station: 0700-0840 

Oden Location when On Station:(82.91, -1.42) - (83.02, -2.04), at 0801 UTC (82.96, -1.76) 

Number of dropsondes: 5 

Sonde times: 0724 (84.86,-25.82), 0732 (84.51,-17.09), 0801 (82.94,-1.62), 0816 (82.28,+3.51) 

Meteorological system phase velocity: 10.5 m/s / 341

Times of direct overflight: 0806

The forecasts with lead times of 48 h or less (Figs. 4.1.1 and 4.1.2) were able to predict 

the general surface pressure structure with a primary low located east of Svalbard, and a trough 

Figure 4.1.1: Sea-level pressure and wind at 12 UTC Aug. 8 (YD221) from ECMWF forecasts of lead time a) 72 h, 

b) 48 h, and c) 24 h. Frame d) shows the analysis at 12 UTC Aug. 8. Oden is marked by the red "X". 
12 

a) 
13 

b)

Figure 4.1.2: a) (on previous page) 24-h forecast of sea-level pressure and 1000-500 hPa thickness from the GFS 

model valid at 12 UTC Aug. 8 (YD221). b) Canadian Weather Service sea-level pressure analysis with frontal 

interpretation at 06 UTC Aug. 8. The time-space-adjusted tracks for the DC8 (red) and Oden (blue) are seen (see 

description of Fig. 4.1.3). 

line with a secondary low extending northwestward from Svalbard over the region of the Oden, 

located at about 83N, 2W at this time. At the Oden, the near-surface wind was from the 

northwest. The satellite image sequence (Fig. 4.1.3) shows not only the low-pressure circulation 

center east of Svalbard (V1), but also two circulation centers NW of Svalbard. Center (V2) is 

moving southward from the NNW and dissipating, though at 06 UTC the circulation with this 

system is very clearly defined, and with an apparent frontal cloud band extending eastward north 
14 

of the Oden's location. Another circulation center (V3) is present at 06 and 09 UTC along the 

NE coast of Greenland, with a less distinct cloud band extending NE from its center. All three of 

these lows are marked on the 12 UTC analysis from ECMWF, though most forecasts did not 

produce the secondary lows. 

Figure 4.1.3: Satellite images at a) 0610 (IR), b) 0926 (IR), c) 0926 (Vis), and d) 1329 (IR) UTC Aug. 8 (YD 221) 

near Greenland, Svalbard, and the North Pole. The system-relative track of the DC8 aircraft (red) and the Oden 

(blue) are shown using a system phase velocity of 10.6 m s-1 from 347. The system-relative locations are shown by 

the marked hours for the DC8 and the 6-hourly locations for the Oden. The 10-min (hourly) positions are shown by 

the "x" ("o") for the DC8 (Oden) track. The dropsondes are marked by "D". In ), c), and d), the red (blue) wind 

barbs are those along the DC8 (Oden) track and height. In a), the red (blue) barbs are the system-relative winds 

along the respective tracks, and the black ones represent system-relative winds at 2 km from the dropsondes and the 

upsondes. The DC8 flew at 6850 m where wind barbs are marked, and above 11 km outside this area. The vortices 

V1, V2, and V3 are marked. 
15 

Utilizing features evident in the satellite images from 0610, 0926, and 1105 UTC, a 

system phase velocity of 10.5 m s-1 from 341 is estimated. Applying this phase velocity to 

adjust the locations of the DC8 and the Oden to the times of the respective satellite images, the 

positions of the two data platforms relative to the main synoptic features can be visualized (Fig. 

4.1.3). The aircraft descended to 6850 m shortly after 07 UTC and flew through the circulation 

center V2, dropping two dropsondes in the main cloud band (one sonde failed) and one 

dropsonde very close to the circulation center. Sonde 12 in the main cloud band showed the 

main cloud top to be at 4700 m, with the air being moist to the surface (Fig. 4.1.4). A layer of 

warm air (T ~ -1C) existed between 1300-2100 m, presumably through horizontal advection. 

The winds were between 300-355 from 500 m to the surface, with the strongest winds of 18 m 

s

-1 occurring between 1300-4000 m from 330-340. Note that no easterly flow, as might be 

expected by the orientation of the cloud band, occurred in this profile. After the circulation 

center, the aircraft passed through a cloud enhancement near the intersection of circulation V2 

and the cloud band extending from V3. The aircraft passed over the Oden in this region, 

dropping a sonde right over the Oden at 0806 UTC at the same time as an upsonde was launched 

from the Oden (Fig. 4.1.5). Compared to sonde 12, sonde 54 showed cooler air aloft, with a 

Figure 4.1.4: Dropsonde profiles from sonde 12 (the second sonde). Panel a) shows temperature (sold blue), dew 

point (dashed blue), potential temperature (solid red), and equivalent potential temperature (dashed red). 
16 

 

 

Figure 4.1.5: Comparisons of data from dropsonde 54 (blue) at 0801 UTC Aug. 8 with the collocated upsonde from 

the Oden (red) showing a) air temperature, b) relative humidity, c) wind speed, and d) wind direction. 

primary cloud deck top at 2 km and a secondary moist layer near 5 km. After dropping one more 

sonde at 0818 UTC, the aircraft ascended at 0840 UTC. Because of a course correction by the 

aircraft, the DC8 flew along the time-adjusted track of the Oden for nearly 15 minutes (0754-

0810 UTC). The Oden sampled this track between 07-10 UTC.

One objective of the simultaneous sondes was to compare the new, Yankee Technology 

dropsondes with the upsondes from the Oden, as done in Fig. 4.1.5. These particular sondes 

showed the dropsonde to be about 1° C warmer than the upsonde, the relative humidity to be 

biased low in the high-humidity region near the surface, and the wind profiles to be in excellent 

agreement. Future intercomparisons of aircraft, dropsonde, upsonde, tethersonde, and remote 

sensing data will determine whether these differences in this case are representative of other 

cases. The low humidity bias of the AMISA dropsondes in the moist regions has been noted in 

other cases.

The track of the Oden crossed the aircraft track near the cloud band from V3 and the 

cloud enhancement in this region. The track then continued northward, east of the aircraft track, 

passing through the E-W cloud band from V2 between 15-17 UTC, though the band had 

weakened by that time (Fig. 4.1.3d). The time-height section from the S-band cloud radar and 

serial rawinsondes on board the Oden show the vertical structure of the cloud features along the 

Oden's track (Fig. 4.1.6). The low and upper-level clouds sampled by the DC8 dropsonde are 

evident, as is the fact that the aircraft was flying along the tops of the mid-level clouds. Note that 

the spectral width of these clouds was quite low, suggesting that they would contain very little 
17 

Figure 4.1.6: Time-height sections from the S-band radar and serial rawinsondes of a) SNR (color), e isopleths 

(C), wind barbs, b) vertical velocity and air temperature (C), and c) spectral width and mixing ratio ( g kg-1). The 

time that the DC8 was over the Oden is marked by a vertical black line. Between 07-10 UTC, the DC8 flew the 

same line as sampled by the Oden, as seen in the satellite images. Regions of potential instability are shaded in a). 

The red stars on the abscissa mark the Oden rawinsondes. 
18 

turbulence and probably very little liquid water. The time period of coincident ship and aircraft 

track (07-10 UTC ship sampling time) included a period of low-level boundary-layer clouds with 

a mid-level cloud deck and a period of more active (perhaps precipitating) clouds extending to 2-

3.5 km altitude. The ship's passage through the cloud band from V2 is marked by two active 

cloud bands near 15 UTC and 17 UTC, with cloud tops reaching up to 5 km, consistent with the 

earlier aircraft sonde showing high moisture up to 4.7 km in this band further to the west. 

The serial rawinsonde ascents show significant layering in the very complex frontal 

structure. The region of enhanced clouds and precipitation near the intersection of circulation 

V2 and the cloud band from V3 (0820-1130 in Fig. 4.1.6) appears to mark a cold-frontal feature 

below 1.5 km, as marked by the 14C e isotherm (Fig. 4.1.6a). However, the cloud band 

marked by the enhanced clouds and precipitation extending eastward from V2 has warm, moist 

air just to its north in an elevated layer between 2.5 - 4.0 km (Fig. 4.1.6b, c). This is in rough 

agreement with dropsonde 12 which sampled this cloud band 10 h earlier and further to the west. 

On the other hand, the e analysis suggests that warm/moist air is located in a layer between 2.5-

5.0 km between the precipitation band at 1130 and that at 1700, apparently contradicting the 

conceptual notion that warmer/moister air is located north of the second precipitation band 

suggested by Figs. 4.1.6b,c). This contradiction may result from temporally interpolating the 

rawinsonde data which has poor temporal resolution. Other remote sensors on the Oden may 

resolve this issue. Stratocumulus clouds with a NNE wind are present north of the cloud band 

extending east from V2, with cloud tops near the top of the strong stable layer. The 60 GHz 

scanning radiometer data (Fig. 4.1.7) show the strong inversion near the tops of the 

stratocumulus clouds at 200-400 m before 08 UTC, and the lifting of this stable layer to 700 m 

and above with the passage of the front at 0830-1130 UTC. 

Though many of the airborne measurement systems were not operating during this transit 

case (e.g., microphysics data), the array of dropsondes and Oden upsondes lends itself to a 

synoptic analysis of the dynamical structure of a complex Arctic frontal system, and an analysis 

of the dynamic forcing of the clouds observed by the remote sensing instruments on the Oden. 

Figure 4.1.7: Time-height series reflectivity from Ka-band radar in lowest 2 km and the retrieved potential 

temperature (K) from the 60 GHz radiometer in the lowest 1 km on YD221 (Aug. 8, 2008). 
19 

4.2 IOP 1; Aug. 12-13 (YD225-226)

Aircraft Takeoff: 18:02:07 Landing:~0346 On Station: 2000-0125 

Oden Location when On Station: (87.5, -1.76) 

Number of dropsondes: 6 ; 

Sonde times(ddhhmmss): 12200519, 12202901, 12204147, 12205703, 13003537, 13010830, 

13012017 

Meteorological system phase velocity from sat images: 14.5 m/s / 81

Low-level cloud (~1 km) phase velocity: 

Times of direct overflight: 22:17:25 (1614 m), 00:06:00 (114 m), 00:35:50 (2388 m) 

After waiting for the Oden to find a solid floe, IOP1 was flown on the evening of Aug. 12 

and the morning of Aug. 13, only a few hours after the Oden had moored at 87.5 N, 1.8 W. 

The objectives of IOP1 were 1) to provide spatial atmospheric sampling near the Oden as a 

major storm system passed over and 2) to obtain a characterization of the ice conditions near the 

Oden drift site using the remote sensors before the end of the summer melt. The major lowpressure system moved from northwestern Siberia over the pack ice between Svalbard, passing 

nearly directly over the Oden and producing a strong low-level flow of warm, moist air from 

Eurasia over the North Pole (Figs. 4.2.1, 4.2.2, 4.2.3, and 4.2.4). The edge of this plume of 

Figure 4.2.1: Canadian Weather Service sea-level pressure analyses at a) 00 UTC Aug. 12, b) 12 UTC Aug. 12, c) 

00 UTC Aug. 13, and d) 12 UTC Aug. 13. The Oden is the reporting station at 87.5 N, 2 W. 
20 

Figure 4.2.2: Forecasts and analysis of sea-level pressure and 10-m winds valid at 00 UTC Aug. 13 from the 

ECMWF model. Shown are a) 72 forecast, b) 48 h forecast, c) 24 h forecast, and d) analysis. 

warm, moist air was forecast to pass over the Oden at about 1.5 km above the surface near 00 

UTC Aug. 13 with reasonable accuracy with 24-48 h lead time (Figs. 4.2.3 and 4.2.4), which 

validations showed to actually happen. 

The sequence of satellite images and satellite-derived winds is used to estimate the 

locations of the surface (or near-surface) fronts (Fig. 4.2.5). In addition, the DC-8 and Oden data 

are used to refine this analysis. During the afternoon of Aug. 12, warm, moist air flowed from 

northern Siberia over first open water and then pack ice in the open wave porion of the frontal 

system. This air was lifted by the warm front and in a diffluent flow, producing clouds in the 

anticyclonic flow above the warm front over the Siberian and Chukchi Seas as well as in the 

cyclonic flow over the Oden. The satellite image at 2142 UTC (Fig. 4.2.5c) shows the classical 

“T-bone” structure (Shapiro and Keyser 1990) of the clouds with this system, which suggests 

that the system developed in an environment of weak barotropic shear. The Oden was located at 

the top of the stem of the “T”. Before the low-pressure center arrived near the Oden, the 

occluded portion of the front passed over the Oden near 2330 UTC Aug. 12 (Fig. 4.2.5c), while 
21 

Figure 4.2.3: Forecasts and analysis of 850 hPa temperature (color) and winds, and sea-level pressure (isopleths) 

valid at 00 UTC Aug. 13 from the GFS model. Shown are a) 72 forecast, b) 48 h forecast, c) 24 h forecast, and d) 

analysis. 

the low passed just south of the Oden near 06 UTC Aug. 13 (Fig. 4.2.5e). The sequence of 

surface winds at the Oden shows the passage of the low just to its south (Fig. 4.2.5c), and the 

intensity of this low is revealed by the strong surface winds and the low central pressure (Fig. 

3.1d). 

The DC-8 collected data in the vicinity of the Oden between ~2000 UTC Aug. 12 and 

0130 UTC Aug. 13 during the time of the frontal passage. The track of the DC-8 and its array of 

dropsondes sampled the “bent-back” portion of the frontal cloud band, the occluded front passing 

over the Oden, and the low-pressure system (Fig. 4.2.5c). The analysis of the “lawnmower 

“flight pattern flown at ~1.6 km altitude shows the passage of the warm front aloft, with warmer 

temperatures and veering winds to the east, along with a significant band of precipitation (Fig. 

4.2.6). While the surface temperatures as recorded at the Oden warmed by less than 1 degree 

during the frontal passage, the temperatures at 1.6 km warmed by 7 degrees. The flow at this 

altitude is convergent, contributing to the lifting and generation of the clouds and precipitation. 
22 

Figure 4.2.4: Forecasts and analysis of temperature (color), winds and height (isopleths) at 850 hPa valid at 00 

UTC Aug. 13 from the FIM model. Shown are a) 60 h forecast, b) 36 h forecast, c) 24 h forecast, and d) analysis. 

The S-band cloud and precipitation radar images overlaid with thermodynamic analyses 

from the Oden rawinsondes show that the cloud tops were near 9 km, with the generating cells 

for the warm frontal clouds aloft located in the low-stability warm air being lifted above the 

warm front (Fig. 4.2.7). Higher cloud tops and enhanced reflectivity occurs at the leading edge 

of the lower-e air that comes in after 2330 UTC, or behind the cold front aloft. A very stable 

layer develops near 1.2 km altitude near 21 UTC Aug. 12, and persists nearly 24 hours. This 

corresponds to the time that the air between 1-2 km is above freezing behind the warm front. 

This layer of warm air produces melting of hydrometeors, with freezing rain and sleet at the 

surface, and shows up as the higher fall velocities in Fig. 4.2.7b. The time-height sections of 

temperature from the scanning radiometer (Fig. 4.2.8) shows brief periods of less stable air at 

approximately the time the cold front passes over the Oden above the stable layer, suggesting 

that frontal passages above the surface influence the stability in the boundary layer. 
23 

 

 

 

Figure 4.2.5: Sequence of AVHRR satellite images showing the synoptic evolution of IOP1. The satellite-derived 

winds and the surface frontal features are shown in each image. The tracks of the DC-8 (green) and Oden (yellow) 

are shown in c) using a phase velocity of 14.5 m s-1 from 81°. 
24 

Figure 4.2.6: Flight level winds and temperature from DC8 between 212040-230320 UTC (red) and surface 

pressure, temperature, and winds from the Oden (blue). The 1.6 km temperature analysis is shown by black 

isopleths. The far right DC8 points are from 2336 and 0015 at ~1.5 km. The DC8 (red) and Oden (blue) tracks have 

been adjusted to the satellite image time of 2142 UTC Aug. 12 (see Fig. 4.2.5c above) using a system phase velocity 

of 14.5 m s-1 from 81. Oden surface data is plotted every 30 min between 2000-0100 UTC, while the DC8 data is 

plotted every 5 min. A composite of DC8 nose radar images between 2303-2339 UTC shows the weak (green) and 

more intense (yellow) precipitation echos. The background shows the cloud band associated with the occluded front 

in Fig. 4.2.5c. 

The enhanced spectral widths near the tops of the warm-frontal generating cells (Fig. 

4.2.7c) suggest enhanced turbulence and the possibility of liquid water in these regions. The 

DC-8 sampled the air above the warm front in some of the generating cells aloft (near 1930 UTC 

at 6.5 km and 2130 and 2220 UTC at 8 km), the air just below the warm front near the time of 

the passage of the cold front aloft and the formation of the low-level stable layer, and behind the 

cold front aloft and above the warm front and stable layers. The DC8 data could be used to 

further understand the formation of this stable layer and the detailed dynamical forcing during 

this crucial transition time. Furthermore, aerosol sampling in the warm air above the warm front 

and stable layer can permit an assessment of aerosol types and amounts emanating from Siberia 

and the near-coastal Arctic Ocean waters. 

During IOP1, the DC-8 made many passes directly over the Oden, and many more passes 

through air that passed over the Oden at times before or after the DC-8 was there (Table 4.2.1). 
25 

Figure 4.2.7: Time-height cross section of a) e (deg C), wind barbs, and S-band SNR; b) temperature (deg C) and 

S-band vertical velocity; and c) mixing ratio (g kg-1) and S-band spectral width. Each panel is overlaid with a 

frontal analysis based primarily on e (heavy red, blue, and purple lines), theDC-8 flight track data (heavy black 

line), radiosonde times (red stars on abscissa & vertical dashed lines), and dropsonde times and height coverage 

(vertical dashed blue lines). The heavy red isopleth in b) is the 0 C isotherm. 
26 

Figure 4.2.8: Time-height sections to 1 km height of the a) temperature and b) potential temperature from the 60 

GHz radiometer on YD 225 through YD226. 

Table 4.2.1: Times for which the time-space adjusted DC8 and Oden tracks are within ~1.4 km of each other for 

IOP1. A phase velocity of 14.5 m s-1 from 81 was used. The last 3 rows show the times when the proximity of the 

tracks occurred with the times within 30 s of each other, indicating a direct overflight. 

Oden Time DC8 Time Altitude (m) Distance(m)

1930-1945 210720-210900 5300-5842 127-1175 

2037-2042 215000-215050 1629-1641 97-1321 

2107-2120 215445-215625 1616-1622 107-1178 

2121-2127 205510-205540 7768-7771 383-934 

2207-2221 221720-221840 1612-1615 171-1336 

" 205030-205055 7754-7757 545-1099 

2231-2233 232030-232050 760-761 240-1336 

2256-2309 223400-223540 1606-1608 171-1216 

2311-2313 235520-235535 144-145 153-1255 

2330-2333 223820-223830 1601-1604 23-1050 

" 002820-002830 2358-2361 545-1034 

2348-2352 230445-230455 986-1048 296-1092 

" 204030-204035 7768-7769 511-895 

2359-0013 233155-233330 742-746 142-1323 

" 000600-000640 111-116 522-1213 

0026-0122 003440-004100 2384-2388 127-1318 

0125-0128 004120-004140 2383-2384 1065-1304 

0136 004235 2384 1291 

0144-0153 004325-004420 2380-2383 939-1296 

 

Direct Overflight (< 30s difference betw. the two times) 

2217 221725 1614 816 

0006 000620 114 643 

0036 003550 2388 487 
27 

4.3 IOP 2; Aug. 15 (YD228)

Aircraft Takeoff: 04:02:00 Landing:~1510 On Station: 0520-1225 

Oden Location when On Station: (87.5, -1.76) 

Number of dropsondes: 4 ; 

Sonde times (ddhhmmss): 15052249, 15070458, 15084038, 15121925 

Meteorological system phase velocity from sat images: 13.9 m/s / 175(all); 12.4/161(north)

Times of direct overflight: 0919, 1144 

Another objective of AMISA was to obtain air samples in airflow trajectories from the 

open water south of the Fram Strait to the Oden near the North Pole to assess whether aerosols or 

cloud condensation nuclei may arrive at the Oden from the marginal ice zone. IOP2 on Aug. 15 

was an attempt to sample such a case. The remnant low-pressure system from two days before 

had filled and positioned itself due north of Greenland (Figs. 4.3.1 and 4.3.2), producing weak 

southerly surface flow through the Fram Strait. This evolution was forecast reasonably well, 

though the verification showed the flow to be a little more from Svalbard rather than straight 

through the Fram Strait (Fig. 4.3.2). The timing suggested that the flow would be more through 

the Fram Strait before 12 UTC on Aug. 15 (Figs. 4.3.3 and 4.3.4). While the flow would be 

southerly, the temperatures at 1.5 km were forecast to be much colder than for IOP1 (Figs. 4.3.3 

and 4.3.4). 

The satellite images (Fig. 4.3.5) show a large vortex in the cloud field north of Greenland 

corresponding to the main surface low, with a cloud band emanating from the NE corner of 

Greenland associated with the front, separating flow through the Fram Strait from that circulating 

north of Greenland. The flight started with two aerosol stacks near the ice edge and another one 

over the pack ice approximately halfway to the Oden from the ice edge (Fig. 4.3.5). These 

aerosol stacks were comprised of 3 legs oriented perpendicular to the wind at ~ 250 m, 1100 m, 

and 1600 m. A third aerosol stack was done over the Oden, and tracks between the stacks 

consisted of slow ascent/descent profiles to ~8000 m, with a dropsonde released at the apex. 

 

Figure 4.3.1: Sea-level pressure and frontal analysis from Canadian Weather Service at 06 UTC and 12 UTC Aug. 

15 (YD228). 
28 

Figure 4.3.2: Forecasts and analysis of sea-level pressure and 10-m winds valid at 12 UTC Aug. 15 from the 

ECMWF model. Shown are a) 72 forecast, b) 48 h forecast, c) 24 h forecast, and d) analysis. 

After the aerosol stack was completed over the Oden, a truncated “lawnmower pattern” was 

flown to again characterize the sea ice conditions. 

Figures 4.3.5 and 4.3.6 show that the flux stacks were performed perpendicular to the 

southerly flow. The low-level cloudiness near stack #2 suggests that the conditions were perhaps 

not homogeneous from the ice edge to the Oden. The condensation nuclei (CN) concentrations 

sampled at the first two stacks show values of ~100-300 cm-3 (Fig. 4.3.6), suggesting that similar 

air was being sampled. The CN values obtained near the Oden within the frontal cloud band 

(Fig. 4.3.7b) show similar values on the east side of the front at 1.6 km altitude, while much 

higher values (~1500 cm-3) were observed on the western side of the cloud band. The 

temperature field at 1.6 km (Fig. 4.3.7a) shows the air to be warmer on the east side, while the 

slow westward movement of the band indicates that it is a warm front. The flow is diffluent at 

1.6 km (Fig. 4.3.7), indicating that the convergence producing the clouds and lifting must occur 

at another level. 

The track of the Oden is very oblique to the front (Fig. 4.3.7), so the time-height sections 

provided by the Oden remote sensors and rawinsondes produce a much more gradual transition 
29 

Figure 4.3.3: Forecasts of temperature (color), winds and height (isopleths) at 850 hPa valid at 06 UTC Aug. 

15(a,c) (78 h & 54 h forecasts) and 18 UTC Aug. 15 (b,d) (90 h and 66 h forecasts) from the FIM model. 

Figure 4.3.4: Forecasts of 850 hPa temperature (color) and winds and sea-level pressure (isopleths) valid at 06 

UTC Aug. 15 (a,c) (54 h and 78 h forecasts) and 18 UTC Aug 15 (b,d) (66 h and 90 h forecasts) from the GFS 

model. 
30 

Figure 4.3.5: Visible (a) and infrared (b) satellite 

images showing the sampled system for IOP2. The 

complete flight track (red line), hour along flight track 

(green), 10-min markers("x"), and ice edge (blue) are 

shown. A wind barb at 1.6 km at the intermediate 

aerosol stack is also shown. No time-space adjustment 

is done to this track (it is geographically correct.) 

Figure 4.3.6: Flight track time-space adjusted to 0637 

UTC overlaid on visible satellite image at 0637 UTC. 

The green numbers show the cloud condensation nuclei 

concentration (cm-3). The heavy blue line shows the ice 

edge.

than would likely be produced with a cross-section perpendicular to the frontal band. 

Nevertheless, analysis of the serial rawinsondes shows the warm-frontal structure above a few 

hundred meters above the surface (Fig. 4.3.8). Multiple layers of potential instability and a 

complex frontal structure in the vertical (as seen on the transit flight case) produces multiple 

cloud layers. The cloud radar also shows variable reflectivity intensity in the low-level 
31 

Figure 4.3.7: Infrared (a) and visible (b) satellite images at 0953 UTC on Aug. 15 2008 showing the analysis of 

temperature (a) and condensation nuclei (CN) (b) at 1.6 km altitude from the aircraft data. The DC8 track (red) 

and Oden track (blue) are time-space adjusted to 0953 UTC using a phase velocity of 13.9 m s-1 from 175. Wind 

barbs from the aircraft (yellow) and Oden (blue) and the Oden hourly surface pressure are also shown. 

stratocumulus clouds, which seems to be correlated with the variability in the low-level 

temperature (Fig. 4.3.9). The only precipitation occurs between 0750-1000 UTC, which 

corresponds to a narrow region of deeper clouds only subtly discernible in the satellite images. 

However, the aircraft crosses this feature on all of its transverse legs (Fig. 4.3.7). 

The DC-8 also flies in various cloud layers, crossing the Oden track at twelve points and 

heights (Table 4.3.1 and Fig. 4.3.8b). If one assumes that the frontal features seen along the 

Oden cross-section in Fig. 4.3.8 are quasi-two-dimensional, the aircraft will cross the features 

from well to the left of the precipitation band to over the low-level stratocumulus on the right at 

the altitudes marked by a “D” in Fig. 4.3.8b. 

The analysis of RHw at 1.6 km shows the very moist conditions at this level, with water 

saturation occurring in a cloud layer at this level near the warm edge of the deeper clouds (Fig. 

4.3.10a). However, when the aircraft later flies eastward at 900 m below and eventually beyond 

this upper cloud layer (Fig. 4.3.10c) and in the top of a lower stratocumulus layer, saturation is 

present in the top of the lower cloud layer at approximately the eastern edge of the upper layer. 

Furthermore, the aircraft descent through this lower layer at an earlier time showed that it had 

near-neutral stratification with a very cold cloud top. [Note that this is the stratocumulus cloud 

for which the 60 GHz scanning radiometer showed strong cooling below 500 m as well (see Fig. 

4.3.9).] Furthermore, liquid water contents of > 15 cg m-3 were observed in the tops of these 

lower clouds at this location (Fig. 4.3.10b,d). This LWC was more than anywhere else during 

the flight. 

We interpret these measurements as indicating that strong cloud top radiative cooling 

occurred in the lower stratocumulus cloud layer in the region where it emerged from underneath 
32 

the upper cloud layers. When the upper cloud layers are present, radiative effects from this 

upper layer probably limit the cloud top radiative cooling possible in the lower cloud deck, hence 

illustrating a mechanism for cloud-layer interactions near frontal systems that can impact the 

cloud characteristics and the surface energy fluxes. The radiation data from the aircraft and at 

the surface will be valuable to further explore this hypothesis. 

Table 4.3.1: Times for which the time-space adjusted DC8 and Oden tracks are within ~1.4 km 

of each other for IOP2. A phase velocity of 13.9 m s-1 from 175 was used. The last 2 rows show 

the times when the proximity of the tracks occurred with the times within 30 s of each other, 

indicating a direct overflight. 

Oden Time DC8 Time Altitude (m) Distance(m)

0918-0920 091910-091925 116-117 301-1346 

0938-0940 093635-093650 740-741 308-1239 

0956-0958 095420-095430 1631-1632 207-1008 

1017-1018 100850-100905 1635-1636 415-1083 

1039-1041 102515-102525 1640-1642 232-1085 

1100-1102 103945-104000 1641-1642 323-1284 

1104 111200-111210 1639-1640 566-979 

1122-1124 105545-105600 1640 459-1337 

1124-1125 112635-112645 1639-1640 720-1220 

1143-1145 114410-114420 107-110 76-1111 

1205-1207 120210-120225 815-816 89-1217 

1427-1438 084020-084105 6988-6994 117-1282 

 

Direct Overflight (< 30s difference betw. the two times) 

0919 091915 117 301 

1144 114415 107 76 
33 

 

Figure 4.3.8: Time-height series analyses of Ka-band radar and rawinsonde data in the lowest 2 km on Aug. 15 

(YD228). Shown are a) reflectivity (color), e (blue), isotachs (red), and wind barbs; b) spectral width (color) and 

temperature (blue). The times and heights of coincident data from the DC-8 (Table 4.3.1) are shown by a "D" in b). 

Warm (red) and cold (blue) frontal analysis based on the e field are shown in both panels. Shaded areas depict 

regions of potential instability and vertical black dashed lines show the rawinsonde ascent times. 

 Figure 4.3.9: MMCR radar reflectivity (color) and potential temperature (0.5 K isopleths) from the 60 GHz 

radiometer for Aug. 15, 2008. 
34 

 

 

Figure 4.3.10: a) Horizontal plot of the aircraft track and relative humidity analysis at 1.6 km overlaid on the 

visible (Ch. 2) satellite image, time-space adjusted to 0953 UTC using a phase velocity of 12.4 m s-1/ 161. The 

Oden track from 08-14 UTC is shown in blue.; b) liquid water content (LWC, cg m-3) measured by the cloudaerosol spectrometer probe on the DC-8 between 115300 and 121000 UTC Aug. 15; c) analysis of relative humidity 

wrt water (RHw, %, thin black solid), virtual potential temperature (solid red, K), and temperature (C, dashed 

blue) using data projected to the cross-section along the black line in a) for data within 90 km of the line. Data 

from the aircraft track (thin blue dashed) and the Oden upsondes (thin blue solid) are used, along with Oden data at 

35 m MSL between 0807 and 1308 UTC. The cloud radar reflectivity from the Oden is also projected to the crosssection, though the observations before 0807 and after 1308 are further than 90 km from the line.; d) same as c), but 

showing cloud liquid water (red, cg m-3), RHw (black solid, %), and radar spectral width (color background). RHw 

> 100% is shaded. A 30-sec running mean filter is used on both RHw and LWC. On the DC-8 track, "x" marks a 10-

minute point, while hours are shown by black numbers. "U" and "D" indicate Oden upsondes and DC-8 dropsondes, 

respectively. 
35 

4.4. IOP 3; Aug. 22 (YD235)

Aircraft Takeoff: 03:58:03 Landing:~1210 On Station: 0530-1045 

Oden Location when On Station: (87.5, -1.76) 

Number of dropsondes: 3 

Sonde times (ddhhmmss): 22053137 22060640 22063724

Meteorological system phase velocity from sat images: 10.3 m s-1/ 191°

Times of direct overflight: Not in vicinity of Oden 

IOP3 was the only observing period not focused on providing data in the vicinity of the 

Oden. Instead, the purpose was to obtain measurements in a thick and uniform cloud band over 

both the pack ice and the open water. These measurements are intended to improve the “storm 

correction” portion of the AMSR-E sea-ice detection algorithm. Because of airspace issues, the 

only possible area for such measurements was in the Fram Strait, and an opportunity for such a 

flight occurred on Aug. 22, 2008, when a slow-moving thick band of clouds moved northward 

through the Fram Strait. A tongue of sea ice extended southward in the center of the Fram Strait 

(Fig. 4.4.1a), so the flight track was executed along the eastern edge of this ice tongue in the 

eastern half of the Fram Strait. The thick, nearly uniform cloud shield associated with this 

system at the time of the flight is shown in Fig. 4.4.1b. This cloud shield, though very coherent 

and fairly deep, was not associated with any major surface pressure perturbation. While a low 

pressure system is suggested to be located on the west side of this cloud band by the satellite 

image (Fig. 4.4.1b), surface analyses only show very weak surface minima along the east and 

north coasts of Greenland (Fig. 4.4.2). 

Figure 4.4.1: Images illustrating the location of the IOP3 flight. a) clear-sky visible satellite image from Aug. 17 

showing the ice edge (purple) and the geographically located flight track from Aug. 22; b) flight track on Aug. 22 

time-space adjusted to the time of the visible satellite image using a phase velocity of 10.3 m s-1 from 191°. The 

dropsonde locations (D) and the hours along the track are shown. The location of the cross-section in Fig. 4.4.3 is 

shown in a), and the location of the ice edge on Aug. 17 is overlain on the Aug. 22 image in b). 
36 

Figure 4.4.2: Surface pressure analyses at 12 UTC Aug. 22, 2008, from a) the Canadian Meteorlogical Service, and 

b) the ECMWF. 

The system phase velocity estimated from the satellite image sequence was 10.3 m s-1

from 191°. The flight track consisted of an upper-level pattern at 8100 m from over the open 

water to well in over the sea ice with 3 dropsondes placed over the open water, at the ice edge, 

and over the ice. These are used to characterize the atmospheric cloud structure. These passes 

were followed by a series of 9 passes in a “lawnmower” type pattern at 1700 m to map out the 

regional sea ice characteristics. At the end, a series of 3 passes at 150 m were then performed to 

characterize the details of the surface conditions (Fig. 4.4.3). At the end, an ascent-descentFigure 4.4.3: Photos taken from 150 m height at a) 0950 UTC and b) 1007 UTC at the NW and SE ends of the legs, 

respectively. a) shows pack ice with many meltponds and some leads, while b) shows open water with the edge of the 

pack ice in the distance. (Photos: R. Wilcox) 
37 

ascent leg oriented diagonally across the rectangle defined by the other legs was done to provide 

some microphysical profiling of the cloud band, with the apex of the first ascent occurring just 

above cloud top. Note that, because of the movement of the cloud system, the dropsondes, the 

1700 m legs, and the 150 m legs with the final ascent/descent/ascent diagonal were done in three 

different areas of the cloud system (Fig. 4.4.1b). Only if it is assumed that the cloud band was 

quasi-homogeneous in the along-band direction can we justify overlaying the data from the three 

different portions of the flight. If we assume that the ice edge is the primary determinator of the 

cloud structure, then the data was collected in the same cloud region.

The vertical cross-section from the sea ice to over the open water (Fig. 4.4.4) shows that 

the cloud top was fairly uniform near 3100 m, with slightly deeper clouds at the eastern edge 

(note that the dropsonde RH was low, with in-cloud values only reaching 90-95%; the aircraft insitu RH instruments were totally unbelievable during some legs and especially during the last 

ascent/descent/ascent profiles, and were hence not used in the cross-section analysis). The 

temperature field and the LWC measurements show indications of cloud top radiative cooling 

near the ice edge, but none further east. The temperature near 200-300 m is +4° C just east of the 

ice edge, with slightly cooler temperatures near the surface and further west (Fig. 4.4.4a). The 

airflow in this cloud band is uniformly from the ENE through its entire depth at the eastern edge, 

veering to southerly at the western edge of the cross-section and near and above cloud top. 

Horizontal fields at 1700 m show slightly greater RHw in the northwestern half of the 

measured rectangle (Fig. 4.4.5). The temperature field showed a weak maximum near the ice 

edge in the middle of the sampled rectangle. The winds show the weak easterly flow to the east 

and the stronger southerly flow at the western end of the domain. The horizontal temperature 

field at 150 m, where one would expect stronger impacts from the surface, shows again a slight 

maximum just SE of the ice edge (Fig. 4.4.6a), with slightly cooler temperatures to the NW over 

the sea ice. However, the temperatures are above freezing at this altitude even over the sea ice. 

Again, the wind field shows the weak easterlies at the SE end of the domain and the stronger 

southerlies over the sea ice. The fields of the main atmospheric parameters showed only very 

subtle spatial variations (e.g., temperature). However, CN showed large variations (Fig. 4.4.6b). 

Over open water, CN values were 300-500 cm-3, while over the sea ice values were up to an 

order of magnitude larger (1000-4500 cm-3). The source of the high CN values over the sea ice 

is unclear. 
38 

a) 

b) 

Figure 4.4.4: Cross -sections showing isopleths of a) RH wrt water (magenta), temperature (deg C; dashed blue), 

and LWC (cg m-3; green) and b) potential temperature (red; K) and wind direction (deg; blue). The aircraft flight 

track is shown in black and the dropsonde locations in dashed black. The RH field is determined solely from the 

dropsonde data and the shaded region shows RHw > 85%. The location of the cross-section is shown in Fig. 4.4.1a . 

The cross-section crosses the ice edge at about 150 km, with the over-ice region to the left. 
39 

Figure 4.4.5: Analysis of temperature (red isopleths) and wind barbs (blue) from horizontal legs at 1.7 km (0650-

0930 UTC) from DC-8 data on Aug. 22, 2008. The aircraft track (black lines) are shown and RHw > 95% are 

shaded. 
40 

a) 

b) 

Figure 4.4.6: Flight legs and data analysis at 150 m of a) air temperature (deg C) and b) CN (cm-3) between 0930-

1023 UTC Aug. 22. The physical position of the ice edge is shown, while the track is adjusted by the system phase 

velocity (10.3 m s-1/ 191°). The wind barbs (blue) are also shown in each panel. 
41 

4.5 IOP 4; Aug. 23 (YD236):

Aircraft Takeoff: 12:04:27 Landing:~2045 On Station: 1424-1831 

Oden Location when On Station: (87.5, -1.76) 

Number of dropsondes: 9 

Sonde times(ddhhmmss): 23142416, 23144336, 23151042, 23152113, 23153709, 23155219, 

23175312, 23181509, 23183031

Meteorological system phase velocity from sat images: 10 m s-1/ 165° 

Times of direct overflight: 1521, 1701, 1719, 1736 

IOP4 occurred the day after IOP3 and sampled the northwestern region of same cloud 

band as it moved northward over the Oden near 87.5° N (Fig. 4.5.1). A very weak low-pressure 

system, analyzed to be located just north of Greenland at this time (Fig. 4.5.2), is likely 

associated with this cloud system. The analysis of the two low-pressure centers in Fig. 4.5.1 is 

only based on the circulations evident in the cloud images. The e analysis based on the 

upsondes from the Oden suggests a very complex frontal structure with this system (Fig. 4.5.3). 

A shallow layer of cold air is capped by a warm front, which gradually brings in much warmer 

air at the surface, thereby ending the “cold snap” period discussed in the introduction. The 

leading edge of the northward moving cloud shield marks a weak cold front that is riding up over 

the warm front (i.e., a warm occlusion). The tethersonde provided extensive sampling of the 

low-level clouds (up to 400 m -- see Fig. 4.5.4) capped by the warm front between 08 and 14 

Figure 4.5.1: Visible satellite image at 1735 UTC Aug. 23 with the DC-8 flight track overlaid (red). A time-space 

adjustment was applied using a phase velocity of 10 m s-1 from 165°. The time-space adjusted Oden track is shown 

(thin blue, and preliminary frontal analyses at ~0.7 km altitude are also shown (heavy blue). The heavy black line 

A-B denotes the location of the vertical cross-sections shown in Fig. 4.5.5. 
42 

 

Figure 4.5.2: Surface pressure analyses at a) 18 UTC Aug. 23 from the Canadian Meteorological Service and b) 00 

UTC Aug. 24, from the ECMWF. 

UTC and in the warm sector after the warm front passed. The deeper clouds and precipitation 

arriving near 1630 UTC at the Oden are associated with a stronger cold front in the layer 1-3 km 

above the surface. This cold front is preceded by the classical low-level wind speed jetmaximum 

shortly after 15 UTC, as seen in the wind profiler data (Fig. 4.5.5). A third cold front arriving at 

about 20 UTC brings in even slightly colder air in the lowest 1.5 km. 

After dropping a dropsonde from 8 km altitude on approach to the Oden area, the DC-8 

aircraft flew a “Z-pattern” at 5.6 km altitude centered on the Oden, deploying dropsondes at the 

corners and the center of the pattern (Figs. 4.5.1 and 4.5.3). This dropsonde array was primarily 

located in the warm sector ahead of the second cold front, though the SW portion of it straddled 

the second cold front. Vertical profiles of dynamically-related parameters (e.g., vorticity, 

divergence, deformation) can be obtained from this dropsonde data, while radiative flux 

divergence of the cloud top at 4.5 km can be obtained from the airborne radiometer data. The 

aircraft then descended to about 100 m, starting a box of sawtooth patterns (slow ascent/descent 

on each side of the box) from 100 m to 3 km. This sawtooth box pattern was done after the 

warm front had passed the Oden and again encompassed primarily the air directly preceding the 

second cold front (Figs. 4.5.1 and 4.5.3). After the sawtooth box pattern, the aircraft performed 

two horizontal legs passing over the Oden and perpendicular to the airflow (and perpendicular to 

the Oden track), one at 100 m and the other at 1200 m (Figs. 4.5.1 and 4.5.4). Both of these were 

done as the clouds thickened and the precipitation began in association with the second cold 

front. Among other objectives, aerosol sampling with the VACC was done during these legs. A 

final pass of the aircraft over the Oden occurred with a slow descent to 100 m from 1200 m, 

followed by a slow ascent continuing to 5.6 km as the aircraft turned back towards the south. 
43 

Figure 4.5.3: Cross-section along the Oden track of e (isopleths) and reflectivity (color) from 00 UTC Aug. 23 to 

06 UTC Aug. 24, 2008. Shown are the DC-8 track (heavy black), the dropsondes (red dashed), the upsondes (blue 

dashed), and the cold and warm frontal analysis (blue and red solid, respectively). The aircraft track was 

calculated using the system phase velocity in Fig. 4.5.1 . The e field is determined from the upsonde data. 

Figure 4.5.4: Time-height section of temperature (thin solid black) from the soundings and the 60 GHz radiometer 

and Ka-band reflectivity (color) in the lowest 2 km along the Oden track in Fig. 4.5.1. The warm front (red) and the 

low-level cold front (blue) are marked. Locations of the upsondes (blue dashed) and dropsondes (red dashed) are 

shown. Also shown are the locations of aircraft ascent/descents (thicker black solid) and two horizontal aircraft 

legs(circled “X”) performed perpendicular to the cross-section. Tethersonde tracks are shown in cyan. 
44 

Figure 4.5.5 : Time-height cross section of isotachs in the lowest 2 km obtained from the 449 MHz wind profiler on 

Aug. 23, 2008 (YD236). 

The final ascent may have passed through some of the high reflectivity bands that were reported 

to have later produced very large snowflakes at the Oden and were generated near cloud top at 

~ 4 km (Fig. 4.5.3). This case also featured tethersonde data sampling the same low-level 

inversion and stratocumulus clouds sampled by the aircraft (Fig. 4.5.4). 

The horizontal legs over the Oden, the southern side of the sawtooth box, the final 

descent/ascent over the Oden, and the 1730 UTC Oden upsonde can be combined into one crosssection oriented nearly west-east (Figs. 4.5.1 and 4.5.6). Analysing the lowest 2 km of this 

cross-section shows that the second cold front produced clearing to the west and the denser 

clouds to the east above 600 m. A wedge of above freezing air was located between about 100 m 

and 500 m above the surface, with slightly warmer air to the east. (The dropsondes at both ends 

of this cross-sections show temperatures that seem displaced in the vertical by 200 meters or so, 

so they were not included in the analysis.) Liquid water amounts of up to 12 cg m-3 were found 

in the clouds above the second cold front, while only values to 5 cg m-3 were found in the clouds 

in the lowest 100-200 m (Fig. 4.5.6b). 

For IOP4, there were nine 2-4 minute periods when the DC-8 track was within 1.4 km of 

the Oden track, and there were 4 direct overpasses of the Oden with the DC-8 (Table 4.5.1). The 

direct overpasses occurred twice at ~134 m, once at 1233 m and once at 5582 m.
45 

Figure 4.5.6: Cross-sections of a) temperature (blue isopleths, deg C), b) potential temperature (red) and liquid 

water content (cg m-3; green), and c) isotachs (blue) and isohyetals (brown) along the line A-B shown in Fig. 4.5.1. 

In each, the regions with RHw>90% (95%) are lightly (darkly) shaded, and the approximate positions of two cold 

frontal surfaces are shown (heavy blue). In a), the temperature data used in the analysis are shown in tenths of a 

degree Celsius, except that the dropsonde data isn’t used in the analysis because of potential height offsets. The 

aircraft tracks are shown as thin grey solid lines in a) and dotted lines in b and c. 
46 

Table 4.5.1: Times for which the time-space adjusted DC8 and Oden tracks are within ~1.4 km 

of each other for IOP4. A phase velocity of 10 m s-1 from 165 was used. The last 4 rows show 

the times when the proximity of the tracks occurred with the times within 30 s of each other, 

indicating a direct overflight. 

Oden Time DC8 Time Altitude (m) Distance(m)

1312-1315 154605-154610 5578-5579 355-1081 

1453-1455 160830-160840 3264-3278 119-1014 

1525-1529 152055-152105 5582 367-1225 

1658-1700 170115-170125 133-134 496-986 

1721-1723 171845-171855 1233-1234 304-1100 

1728-1731 144950-144955 5574 632-1194 

1731-1734 173540-173555 128-143 421-1079 

1751-1754 163010-163020 3141-3229 357-1045 

 

Direct Overflight (< 30s difference betw. the two times) 

1521 152100 5582 

1701 170115 133 

1719 171855 1233 

1736 173555 134 
47 

4.6 IOP 5; Aug. 25 (YD238)

Aircraft Takeoff: 08:51:03 Landing:~1923 On Station: 1150-1700 

Oden Location when On Station: (87.5, -1.76) 

Number of dropsondes: 9 

Sonde times(ddhhmmss): 25110447, 25113048, 25114447, 25120521, 25122302, 25124021, 

25125911, 25165422, 25172139 

Meteorological system phase velocity from sat images: 15.8 m/s / 254(upper clouds),

Low-level cloud (~1 km) phase velocity: 5 m/s / 290(low clouds) 

Times of direct overflight: 1223, 1352, 1433, 1512, 1555, 1632 

The purpose of IOP5 was to sample a “pure stratocumulus” cloud case, with no frontal 

passages complicating the interpretation. The surface pressure analysis showed a weak pressure 

gradient over the Oden region, though with a surface flow pattern that was fairly complicated 

(Fig. 4.6.1). Forecasts of high humidity at low levels and weak pressure gradients made Aug. 25 

a likely candidate for obtaining a simple stratocumulus cloud field (Fig. 4.6.2). The sequence of 

infrared satellite images shows the non-descript grey signature of the low-level clouds over the 

Oden on this day (Fig. 4.6.3). Unfortunately, it also shows a patch of higher clouds, which in 

further analysis appears to be associated with a jet streak near 500 mb. This patch of higher 

clouds moves over the Oden between 0930 and 1430 UTC (Fig. 4.6.3c-d and Fig. 4.6.4) between 

Figure 4.6.1: Analyses of sea-level pressure from a) the Canadian Weather Service and b) the ECMWF at 12 UTC, 

Aug. 25, 2008. 
48 

 

 Figure 4.6.2: a) 12h forecast of the sea-level pressure and 850 mb mixing ratio (g kg-1) from the UK Met Office, b) 

24 h forecast of sea-level pressure, 925 mb relative humidity (%), and wind barbs from the NCEP GFS model, and 

c) 24 h forecast of sea-level pressure and 10-m winds from ECMWF. No 24-h forecast from the FIM model was 

available. All forecasts are valid at 12 Z Aug. 25, 2008. 
49 

3 and 6 km altitude. Since the DC-8 arrived in the vicinity of the Oden near 1130 UTC and left 

near 1630 UTC, the first 3 hours of the mission sampled while a double cloud deck existed, and 

the last two hours sampled conditions during a pure stratocumulus cloud deck. In addition, the 

transition from a double-layered cloud deck to a single-layered cloud deck was captured for this 

case. Because the phase velocity of the mid-level clouds were much different than that in the 

low-level stratocumulus clouds, two phase velocities are determined for this case. The purpose 

of the analysis determines which phase velocity is the relevant one. 

The first portion of the flight consisted of a “lawnmower” flight pattern at 8 km altitude 

near the back edge of the mid-level cloud deck. The purpose of this pattern was to document the 

Figure 4.6.3: Sequence of infrared satellite images showing the location of the Oden (blue circle) and the movement 

of the mid-level cloud patch on Aug. 25, 2008 (YD238). 

0825 0633 Ch5 0825 0949 Ch5 

0825 1335 Ch5 0825 1827 Ch5 
50 

spatial structure of the sea ice characteristics in the region of the Oden and to obtain a spatial 

array of dropsondes. Figure 4.6.5c shows the spatial location of this high-level flight pattern and 

the dropsondes using the phase velocity of the mid-level clouds. Figure 4.6.4 illustrates that 

many of these dropsondes penetrated both cloud layers. After the high-level pattern, the aircraft 

descended to ~110 m and began a sawtooth ascent/descent box pattern around the Oden starting 

at 13:23:53 UTC. With apices at ~1950 m, the top of this box was above the tops of the 

stratocumulus cloud deck. The north-northeast end of this box was underneath the mid-level 

cloud deck (Fig. 4.6.5c), while the south-southwest end was in only the stratocumulus deck 

After the sawtooth pattern, “racetrack” legs at 110 m, 630 m, and 1000 m were flown. The 

racetrack leg at 1000 m was only partially completed when icing conditions prevent good 

sampling from the LARGE and VACC, so a leg was flown at 1680 m. Another lower leg was 

then flown in the clear air at 1250 m above the stratocumulus clouds, before a final 

descent/ascent was done over the Oden into the low-level wind. The lower portion of the flight 

track projected onto the track of the Oden and the Ka-band cloud radar reflectivity field is shown 

in Fig. 4.6.6. Note that the time that the aircraft spent near the Oden corresponded to a time 

when the tops of the low-level stratocumulus clouds began an increase from their depth of about 

700 m to about 1600 m. At this time, the reflectivity field also shows a low-level clearing from 

~1340-1520 UTC. The tethersonde sampled many of the same clouds during this day up to a 

height of ~600 m. The profile centered on 17 UTC may be especially useful for comparison to 

the aircraft data. 

The wind shifted from SE to W in the boundary layer near 09 UTC, and from S to W 

above the boundary layer near 11 UTC (Fig. 4.6.7). For much of the day, the stratocumulus 

cloud layer had weak winds. However, the rise in the stratocumulus cloud tops corresponds to a 

time when a low-level jet of northwesterly flow forms below cloud top, eventually becoming 

centered between two distinct stratocumulus cloud layers by the end of the day. Hence, while 

Figure 4.6.4: Cross section along the Oden path of radar reflectivity from the Ka-band cloud radar on Aug. 25, 

2008 (IOP5). The aircraft track projected on the cross section is shown (blue solid), and the dropsonde and 

upsonde locations are shown as red and blue dashed lines, respectively. The track ahs been adjusted using the phase 

velocity of the upper-level clouds (15.8 m s-1 from 254 °) 
51 

Figure 4.6.5: Zoomed satellite images at 1335 UTC showing the aircraft flight track a) on a visible image using the 

phase velocity of the low-level clouds, b) infrared image with the low-level phase velocity, c) a visible image with 

the phase velocity of the upper-level clouds. Panels a) & b) show an analysis of temperature at ~630 m altitude, 

while panel c) shows LWC at ~630 m (100-300 m below cloud top of lower clouds). Panel d) is the same as c), 

except showing a LWC analysis using the phase velocity of the lower-level clouds. 
52 

Figure 4.6.6: A 2 km high cross section along the Oden path of radar reflectivity from the Ka-band cloud radar on 

Aug. 25, 2008 (IOP5). The aircraft track projected on the cross section is shown (blue solid), and the dropsonde 

and upsonde locations are shown as red and blue dashed lines, respectively. The track has been adjusted using the 

phase velocity of the lower-level clouds (5.0 m s-1 from 290 °). The tethersonde track is also shown (thin red solid). 

the stratocumulus clouds are the primary cloud structure during IOP5, synoptic or mesoscale 

changes appear to be linked to changes in the cloud characteristics and the kinematic structure. 

The temperature and wind field at the ~630 m height shows a slightly weaker wind with a 

more northwesterly component at the northern end of the pattern compared to the southern end 

(Fig. 4.6.5a,b). A weak temperature gradient existed, with the coldest temperatures at this 

height occurring in the middle of the pattern. The liquid water content was ~5-10 cg m-3 at this 

height (Fig. 4.6.5d), with most of the liquid water occurring in the area not under the upper-level 

cloud (Fig. 4.6.5c). Vertical cross-sections along the wind direction passing over the Oden (blue 

line in Fig. 4.6.5d) show that the coldest temperatures occur ~100 m below cloud top with a 

Figure 4.6.7: Isotachs( m s-1) and wind barbs from the low mode of the 449 MHz wind profiler in the lowest 2 km on 

Aug. 25, 2008. The heavy black lines mark the cloud edges from the MMCR reflectivity in Fig. 4.6.6. Note that the 

x-axis is reversed from Fig. 4.6.6, with the beginning of the day on the left side rather than the right. 
53 

strong inversion right at cloud top (Fig. 4.6.8a). Note that the cold temperatures rise in elevation 

as the cloud top rises. The v field shows only weak or near-neutral stability below cloud top 

(Fig. 4.6.8b), but quite strong stratification at and above cloud top. This holds true for the v

field derived from the scanning radiometer as well (Fig. 4.6.8c). A liquid water content 

maximum of 10-15 cg m-3 is seen ~100 m below cloud top on the aircraft descent profile and one 

of 5-10 cg m-3 on the ascent (Fig. 4.6.8b). 

During this flight, the DC-8 passed over the track of the Oden eleven times, with all but 

one of these passes having a duration of just a few seconds (Table 4.6.1). The aircraft 

descent/ascent over the Oden between 162045-163310 lasted for ~12.5 minutes, however. 

Direct overflights occurred on 6 occasions. 

 

Figure 4.6.8: A 2 km high cross section along the Oden path of radar reflectivity (a,c) and spectral width (b) from 

the Ka-band cloud radar from ~1030-1920 UTC on Aug. 25, 2008 (IOP5). The aircraft track along and within 5 km 

of the cross-section is projected on the cross section (magenta), and the dropsonde and upsonde locations are 

shown as red and blue dashed lines, respectively. The isopleths analyses utilize both the aircraft and the 

dropsonde/upsonde data and show fields of a) temperature (°C) and b) potential temperature (K) and LWC (cg m-3). 

In c), isopleths of potential temperature from the 60 GHz scanning radiometer are shown. The track has been 

adjusted using the phase velocity of the lower-level clouds (5.0 m s-1 from 290°). 
54 

Table 4.6.1: Times for which the time-space adjusted DC8 and Oden tracks are within ~1.4 km 

of each other for IOP5. A phase velocity of 5 m s-1 from 290 was used. The last 6 rows show the 

times when the proximity of the tracks occurred with the times within 30 s of each other, 

indicating a direct overflight. 

Oden Time DC8 Time Altitude (m) Distance(m)

1203-1709 162045-163310 138-1735 127-1175 

1210-1228 122250-122315 7946-7948 225-1180 

1225-1231 133200-133210 674-771 331-1168 

1310-1317 141300-141315 121-122 325-1084 

1345-1352 135145-135200 127-130 171-1336 

1351-1357 145215-145225 620-621 82-1347 

1429-1436 143235-143250 128-130 85-1305 

1436-1443 153850-153900 1641-1642 193-1250 

1510-1516 151200-151210 632-633 217-1216 

1544-1603 125235-125300 7926-7928 173-1270 

1553-1600 155520-155530 1643-1644 308-1160 

 

Direct Overflight (< 30s difference betw. the two times) 

1223 122300 7946 744 

1352 135145 129 1311 

1433 143250 128 865 

1512 151200 632 573 

1555 155520 1643 652 

1632 163145 730 1100 
55 

5. AMISA Summary and Science Issues 

The AMISA field program succeeded in collecting data useful for analyzing the ice 

surface characteristics, the synoptic/mesoscale atmospheric structure, the cloud microphysical 

structure, and the aerosol concentrations and types during six flights in August 2008. Five of the 

flights were directly in the vicinity of the Oden ice breaker and its associated ice camp near 87.5°

N, 5° W. and one was over the ice edge in the Fram Strait. This report summarizes the 

meteorological context of each flight and provides a first look at some of the meteorological 

data. Integration of the aircraft, ship, and satellite data is a key aspect for understanding the 

context of the data for each flight. Through the utilization of the phase velocity of the 

meteorological system obtained from either serial satellite images or from wind speeds at the 

steering level of the clouds, the system-relative position of the aircraft data and the Oden-based 

data can be mapped, and represents an illustration of the integration that has been begun. This 

report illustrates the importance of doing such integration. 

It is shown that the AMISA flights succeeded in bracketing the end of the summer melt 

season, which was a major objective. It has also been shown that the meteorological conditions 

for all flights, with the possible exception of IOP5, included significant impacts from synoptic 

weather disturbances. 

The first-look at the AMISA/ASCOS integrated data set suggests that observations exist 

to address the following science issues: 

1) Instrument intercomparisons: Through the use of a system phase velocity, data from all 

platforms can be placed in meteorological context and be compared to each other. Such an 

intercomparison is crucial for properly integrating the AMISA and ASCOS data sets and 

obtaining the most value from the data. Such an intercomparison will also provide useful 

information regarding the performance of various instrument systems. Data from all IOPs 

can be used for this purpose. 

2) Document the evolution of the surface characteristics during the end of the surface 

melt and onset of freeze-up: The flight patterns of IOPs 1, 2, 4, and 5 all contained 

components from which the ice surface characteristics can be obtained. 

3) Determine to which extent synoptic/mesoscale disturbances produce changes in the 

clouds, thermodynamic structure, and surface energy budget: Because all cases, except 

IOP3 and possibly IOP5, had obvious influences from synoptic/mesoscale disturbance, this 

issue can be examined in four or five of the IOPs, including the transit IOP. In addition, the 

successful collection of sub-hourly surface energy budget data during ASCOS (Sedlar et al. 

2010) will allow the assessment of the synoptic/mesoscale impact on the surface energy 

budget. IOP1 was an especially strongly synoptically forced case. 

4) Document quantitative measurements of radiative flux divergence, liquid water 

content, cloud radar parameters, and the thermal and kinematic atmospheric structure 

for stratocumulus clouds: Data from IOPs 2, 4, and 5 are especially well suited for this 

purpose. 

5) Assess the relative importance of dynamic and radiative forcing for cloud 

microphysical and thermodynamic structure of stratocumulus clouds: This objective 

depends on having obtained a well-placed array of dropsondes in a case of significant 
56 

amounts of stratocumulus clouds in order to assess the dynamical forcing. IOPs 4, and 5 had 

such arrays. IOP2 also obtained a good dropsonde array, but the amount of stratocumulus 

clouds were more limited. 

6) Assess the impact of synoptic/mesoscale flow and vertical mixing on aerosol 

types/concentrations near Oden site: IOP1 had obvious strong long-range transport to the 

free troposphere above the Oden. The transport of aerosol from the ice edge to the Oden was 

documented in IOP2. Flight legs appropriate for aerosol typing with VACC were also 

obtained in IOPs 4 and 5. 

7) Improve NASA AMSR-E algorithm "weather" corrections for satellite sensing 

of sea ice conditions: IOP3 was dedicated to this objective. 

Acknowledgements

The work of Dr. Albin Gasiewski, project PI, was key for the successful planning and execution 

of AMISA, with support from co-PIs Don Cavalieri and Michael Tjernström. The extraordinary 

efforts provided by Eric McIntyre, David Kraft, and Barbara Brooks were a major reason for the 

success of the data collection. The assistance of Ellen Sukovich, Ankita Chartuvedi, James 

McQuaid, Andreas Beyersdorf, and Terry Latham during the field program was essential. The 

enthusiastic and professional support of the crew and staff of the NASA DC-8, especially Chris 

Jennison, Richard Ewers, William Brockett, Ryan Lubinski, and Rick Shetter, is greatly 

appreciated. Their willingness to adapt to time and flight patterns helped us achieve the goals of 

the research missions. The aircraft proved to be a very reliable and capable platform for this 

research. Expert and enthusiastic ground support was provided by Peter Salomonsson and Kurt 

Maki. We are grateful for the loan of the CAPS and LARGE probes, facilitated by Bruce 

Anderson of NASA Langley. Ellen Sukovich processed some of the aircraft microphysical data 

used in this report. Processing of ASCOS data directly contributing to this report has been done 

by Matthew Shupe, Paul Johnston, Vladimir Leuski, and David Carter. Special-area, highresolution satellite data over the area of interest was made available to the AMISA project in real 

time by the Dundee, UK, Satellite Receiving Facility. Jeff Key at CIMSS, University of 

Wisconsin-Madison, provided Arctic-basin polar orbiter images and satellite winds. 

Meteorological surface analyses were graciously made available in real time by Nicole Bois at 

the Canadian Meteorological Center of Environment Canada. Special product forecast charts 

were provided in real time by the UK Met Office, Stan Benjamin at NOAA/ESRL (FIM model), 

and Esbjörn Olsson at the Swedish Meteorological and Hydrological Institute (ECMWF surface 

forecasts). Funding was provided by a grant from NASA to the University of Colorado. 
57 

6. References 

Andreas, Edgar L, and S. Ackley, 1982: On the differences in ablation seasons of Arctic and 

Antarctic sea ice. J. Atmos. Sci., 39, 440-447. 

Martin, S., and E. A. Munoz, 1997: Properties of the Arctic 2-m air temperature for 1979-present 

derived from a new gridded data set, J. Clim, 10, 1428-1440. 

Persson, P. O. G., and A. Solomon, 2008: “Impact of Synoptic and Mesoscale Disturbances 

on the Beginning and End of the Summer Melt Season over Sea Ice”, First-year annual 

progress report to the National Science Foundation, Sep. 2007- July 2008, NSF Grant ARC 

0714053. 

Rigor, I. G., R. L. Colony, and M. Seelye, 2000: Variations in surface air temperature 

observations in the Arctic, 1979-97. J. of Climate, 13 (5), 896-914. 

Sedlar, Joseph, Michael Tjernström, Thorsten Mauritsen, Matthew Shupe, Ian Brooks, Ola 

Persson, Cathryn Birch, Anders Sirevaag, and Caroline Leck, 2010: A transitioning 

Arctic surface energy budget: the impacts of solar zenith angle, surface albedo and cloud 

radiative forcing. In preparation for Clim. Dynamics. 

Shapiro, M. A. and D. Keyser, 1990: Fronts, jet streams and the tropopause. Extratropical 

Cyclones, The Erik Palmén Memorial Volume, C. W. Newton and E. O. Holopainen, Eds., 

Amer. Meteor. Soc., 167-191.