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ATD Achievements - Research Select from: Strategic Initiatives Community Research

DRAFT - TO BE PUBLISHED 12/18

Strategic Initiatives - Select From: Water Cycle Biogeosciences UT/LS Wildfire

Water Cycle Across Scales

The NCAR Water Cycle Across Scales initiative has as its primary goal to understand how water vapor, precipitation, and land-surface hydrology interact across scales to define the hydrological cycle, and to use this information to improve both large and small scale weather prediction and climate models. For more information on the initiative, visit NCAR's Water Cycle webpage.

IHOP Research

Utilizing funding from the NCAR USWRP, NCAR Watercycle Across Scales program and base ATD NSF funding ATD Scientist Jim Wilson conducted the research and submitted a paper to a special IHOP issue of Monthly Weather Review. The paper is entitled Summary of Convective Storm Initiation and Evolution During IHOP: Observational and Modeling Perspective. Please see the RAP IHOP research section for a discussion of this research.

The dropsonde humidity data have not been fully utilized due to lack of knowledge of performance of the dropsonde humidity sensor. The performance of dropsonde humidity sensor is evaluated by using dropsonde data collected from DYCOMS-II and IHOP_2002. The evaluation found no systematic dry bias in dropsonde humidity data as suggested by previous studies.

ATD scientists Dave Parsons and June Wang worked with other investigators in NCAR's Climate & Global Dynamics Division (CGD) to compare these detailed observations taken during IHOP_2002 against similar simulations of the region conducted with the Community Climate System Model. A particular point of interest is to understand why the diurnal cycle in the climate model has an afternoon rainfall maximum instead of the region's well known nocturnal maximum in order to improve the performance of the climate model. The observed and simulated diurnal cycles in humidity are also quite different. The model performance on the wind and temperature appears much more promising.

Parsons and Wang are also working on understanding why nocturnal convective systems can occur over the arid western portions of the Southern Great Plains despite a stability profile that is not conducive to the presence of deep convection. The work is focusing on undular bores showing that such features are quite common over this region and appear to work to maintain nocturnal convective systems by creating a more favorable environment through widespread lifting ahead of these systems.

The S-Pol radar refractivity retrieval uses return from ground targets to provide a map of low-level refractivity, a proxy for low-level moisture. ATD scientists Jim Wilson, Tammy Weckwerth, Crystal Pettet worked to validate the S-Pol radar refractivity retrieval using a variety of diverse measurements from IHOP. Comparisons convincingly show that the retrieval provides an accurate representation of low-level atmospheric refractivity. Under most daytime summertime conditions, radar refractivity measurements are representative of a ~250-m deep layer. Wilson, Weckwerth and Pettet also performed analysis on the utility of refractivity for short-term forecasting applications. They found that the refractivity field may detect low-level boundaries prior to the more traditional radar reflectivity and Doppler velocity fields showing their existence. Data from two days in which convection initiated within S-Pol refractivity range suggest that the refractivity field may exhibit some potential utility in forecasting convection initiation. This study suggests that unprecedented advances in mapping near-surface water vapor and subsequent improvements in predicting convective storms could result from implementing the radar refractivity retrieval on the national network of operational radars.

Other Water Cycle research includes:

Using S-Pol and mobile Doppler radar, radiosonde, TAOS, mobile mesonet, fixed surface station, and airborne water vapor DIAL data from IHOP to understand details and evolution of horizontal and vertical distributions of water vapor in the quiescent boundary layer;

• Using serial radiosonde ascents from many sites to assess the representativeness and evolution of soundings which are typically used to forecast daily convective potential
• Evaluating a convection initiation case study of low-level internal gravity waves intersecting an outflow boundary.

Wang, working with new ATD scientist Liz Zhang, hypothesized that the intersection regions result in increased boundary layer moisture and stronger updrafts and thus a greater likelihood of convection initiation at those locations. A project, entitled “Deriving a Global, 2-Hourly Atmospheric Precipitable Water Dataset from GPS Measurements and its Scientific Applications”, is supported by NCAR Director Office Opportunity fund. The goals of the project are to develop an analysis technique for deriving a near real-time, global, 2-hourly data set of atmospheric precipitable water (PW) using existing ground-based GPS measurements of zenith path delay (ZPD) and to use the PW data to study global PW diurnal variations and quantify errors/biases in global radiosonde humidity data.The development of the analysis technique is nearly complete.The preliminary analysis of one-year PW data shows the potentials for using the dataset to monitor the quality of global radiosonde humidity data, which has always been a challenge.

Biogeosciences (top)

The overarching objective of NCAR’s Biogeosciences Initiative is to incorporate relevant aspects of the biological sciences into geophysics and atmospheric research. In FY04, ATD has contributed in a number of ways to the objectives outlined in the Initiative, which is a 5-year NSF-funded collaborative project involving the University of Colorado, Colorado State University, University of Miami as well as NCAR’s ATD, Atmospheric Chemistry Division (ACD) and MMM.

Airborne Carbon Dioxide and Carbon Monoxide Measurements

Collaboration between ATD, CGD, and the Biogeosciences Initiative has been in place for several years to fund development and field support of airborne facility in situ trace gas instruments. Supported developments include water vapor and fast-response ozone measurements in addition to carbon dioxide and carbon monoxide. The activities have been successful on several fronts in maintaining and improving the quality of requestable instrumentation and data sets.

The airborne CO2 instrument was modified to enable flux measurements by the eddy covariance method. Performance during the Gulf of Tehuantepec (Ocean Waves - also see GOTEX) and Airborne Carbon in the Mountains (ACME) experiments allowed assessment of measurement capabilities. Spectral analysis of Ocean Waves marine boundary layer data imply an instrument frequency response of 4-Hz, and time series analysis implied a mixing ratio measurement precision of 0.2 - 0.3 ppmv (1-? for a 1-second average). The flux artifact of this sensor due to air motion sensitivity was quantified in both marine and terrestrial boundary layer environments during both missions by introduction of calibration gas into the sample cell during a portion of a boundary layer transect. A small artifact due to correlated air motion sensitivity was observed in Ocean Waves data at frequencies lower than 2 Hz, however, the amplitude of these fluctuations is a factor of 50 smaller than the equivalent power spectral content of ambient data obtained in the marine boundary layer at the same altitude. Preliminary ACME results from intercomparison to analyses of flask samples (H. Graham, R. Keeling, Scripps Institute of Oceanography) imply an accuracy of ± 0.2 ppmv. This result has been reproduced by intercomparison to CME ground network working standards provided and analyzed by the CO2 calibration facility (B. Stephens, ATD).

Airborne Water Vapor Measurements

The commercial NCAR open path diode laser absorption hygrometer was modified to improve accuracy of lower tropospheric water vapor mixing ratio observations and to increase the time response of the instrument from an 8-Hz sampling rate to 18-Hz. The modified laser hygrometer performed well as an experimental measurement on the second Alliance Icing Research Study (AIRS-II) and Ocean Waves experiments. Results from the AIRS-II mission established confidence in the accuracy of clear sky water vapor measurements to be +/- 5%, relative to chilled mirror sensors on the same platform. Preliminary results from the Ocean Waves data have confirmed the capability of this sensor to measure vertical fluxes by the eddy covariance method. Spectral analysis of 18-Hz data from boundary layer transects agree well with lyman alpha hygrometer data.

To increase confidence in the absolute accuracy of all NCAR facility water vapor measurements, an accurate, large dynamic range water vapor calibration system was purchased. This commercial system includes a humidity generation system and a certified reference sensor with traceability to both the US and UK standards organizations. Both cover a dew point range of -80º to +20º C, and the reference sensor accuracy is ± 0.1º C in the -60º to +20º C range and ± 0.2º C in the -80º to -60º C region. These efforts are co-sponsored by NCAR's ACD, the Biogeosciences Strategic Initiative, and NCAR Directorate.

Wisconsin Tall-Tower Atmospheric O2 Measurements

ATD concluded three and half years of atmospheric O2 measurements at the WLEF tall tower research site, and returned equipment to the lab for reconditioning while future deployments are considered. Britt Stephens presented an invited seminar on these measurements at the APO Conference in Jena, Germany (poster) and several publications based on this work are in preparation.

Synthesis of Global Light Aircraft CO2 Data

In collaboration with Colorado State University, NOAA Climate Monitoring and Diagnostics Laboratory (CMDL), Le Laboratoire des Sciences du Climat et l'Environnement (LSCE - France), University of Heidelberg (Germany), Max Planck Institute for Biogeochemistry (Germany), Tohoku University (Japan), National Institute for Environmental Studies (NIES - Japan), and Commonwealth Scientific and Industrial Research Organisation (CSIRO - Australia), ATD has completed a synthesis of vertical profile CO2 data from 20 sites around the world to define the vertical distribution of CO2 in the atmosphere. These results have been compared to output from the 16 TransCom 3 Project models to test their representation of vertical tracer transport. B. Stephens presented an invited seminar on this project at NOAA CMDL and a publication based on this work is in preparation.

Wildfire (top)

A long term objective of the NCAR Wildland Fire Initiative is to acquire a research quality data set that will address outstanding scientific questions being investigated by fire researchers. In FY04, ATD's Julie Haggerty, NCAR's Mesoscale & Microscale Meteorology Division's (MMM) Janice Coen, and NCAR's Research Application Program's (RAP) Jeff Cole began development of a preliminary experimental plan and logistical strategy. Motivation for conducting such an experiment includes:

1. acquisition of a comprehensive data set with appropriate spatial and temporal resolutions to be used as input for and verification of fire behavior models;
2. corroboration of previous data sets;
3. better characterization of atmospheric conditions than is available from previous experiments.

The experimental plan lists desired measurements (e.g., fuel inventories, emissions, and atmospheric conditions) and proposes types of platforms and sensors that should be used to acquire the necessary measurements. Required spatial and temporal resolutions are also defined. The major challenges involved in deploying sensors in a burning environment are considered. Discussions continue with interested scientists in the Wildland Fire Initiative and in the larger Wildland Fire Collaboratory; refinements to the experimental plan will continue in FY05.

Upper Troposphere-Lower Stratosphere Strategic Initiative (top)

The Upper Troposphere and Lower Stratosphere (UT/LS) region is of critical importance for understanding long-term climate change. Here ozone is an effective greenhouse gas, and water vapor, cirrus clouds, and aerosols have a strong influence on radiation balance. It is also a region where transport processes that couple the stratosphere and troposphere occur on a multitude of scales and where multiphase chemistry and cloud microphysical processes influence the variability of ozone and water vapor, and hence affect long term climate change. The joint ATD/ACD Analytical Photonics & Optoelectronics Laboratory (APOL) addresses the development and employ of new advanced technologies, instruments, and advanced algorithms for improved ground-based and airborne measurements of various trace gases, which supports the UT/LS Initiative. For more detail on this effort, visit APOL.

Community Collaborations/Ongoing Research - Select From: Terrain-induced Waves and Rotors Scanning Radar Wind Field Measurements Boundary Layer Turbulence and Fluxes Airflow in Complex Terrain VTMX Data Analysis Satellite Icing Retrievals Tropospheric Photochemistry ICE Melt Pond - Arctic Sea Ice

  In addition to our state-of-the-art observing facilities, field support and data services, ATD plays another important role in the atmospheric research community - that of collaborative scientific research and analysis of data gathered from field projects. In FY 04, ATD collaborated with scientists from all over the globe to further understand such atmospheric phenomena as terrain-induced waves and rotors, airflow across rugged terrain, turbulence and fluxes in the boundary layer, ambient formaldehyde, and ice propagation.

Remote Sensing of Terrain-Induced Waves and Rotors (top)

Terrain -Induced Waves and Rotors can pose severe aeronautical hazards and have been cited as contributing to numerous aircraft upsets and accidents involving commercial, military and civilian aviation. Rotors can pose severe aeronautical hazards and have been cited as contributing to numerous aircraft upsets and accidents involving commercial, military and civilian aviation. To aid in our understanding of this sometimes costly and dangerous phenomena, ATD scientists Steve Cohn and Bill Brown collaborated with investigator Dr. Vanda Grubisic from the Desert Research Institute (DRI) as well as the Naval Postgraduate School (NPS) in the Terrain-Induced Rotors experiment (T-REX), of which the Sierra Rotors project is a part. ATD's research focused on studying the ability of remote sensors to diagnose wave and rotor motions. Continuous periods of upward or downward motion seen in the vertical beam of a wind profiler are indicative of a mountain (stationary) wave. Broad spectral widths, observed as the second moment of a clear air Doppler spectrum or as the fading time of a spaced antenna measurement, indicate large velocity variance with the radar integration volume. This large variance can be due to turbulence associated with rotors.

The figure to the left (click for full-sized image) shows vertical wind speed and spectral width measured with MAPR on a 3 day period of the Sierra Rotors project when mountain waves were forecast. Velocities shown in the upper frame are colored red for strong upward motion and blue for strong downward motion. These strong motions indicate waves. The lower frame shows the spectral width during the same period. Most broad widths (red) correspond to times and altitudes where wave motion is also seen. The presence of vertical motion without broad widths may indicate weaker waves that are not generating a rotor circulation. Periods of broad width with little vertical motion may indicate that the stationary wave above the profiler has a near zero phase.

Although there is some ambiguity in interpreting profiler data alone, rawinsonde measurements are available to show gross vertical motion, an array of surface meteorological stations show flow reversal from rotors, and modeling studies will assist in interpretation of this data. The figure to the left (click for full-size) shows the ascent rate of a rawinsonde released from the MAPR site. The typical ascent rate of about 4 ms-1 is drastically modified as the balloon is carried first up at more than 10 ms-1 and then down at more than 4 ms-1 by wave motions. A mobile ISS (MISS) was also deployed to make measurements from alternate locations around the valley.

Scanning Radar Wind Field Measurements (top)

A series of experiments involving scanning a radar with multiple receiving antennas was completed in FY2004. A normal scanning radar with a single receiver can only make direct wind measurements along the beam of the radar (using the Doppler effect), and can only make a full 3-D wind measurement using derived techniques such as target tracking or dual-Doppler (requiring two radars). This experiment used the ISS group’s MAPR wind profiler to investigate techniques to make direct full 3-D wind measurements using multiple receivers. MAPR uses spaced antenna techniques to make a cross beam wind measurement, as well as along beam wind measurement using Doppler shift. Normally MAPR just points vertically; for this experiment it was mounted on a pedestal, tilted and slowly scanned in the azimuth direction to produce a simple scanning radar. The beam width of MAPR is about 10 degrees, much broader than a traditional scanning radar, and the range was limited to about 20 km, however the radar did prove to be a useful platform for testing wind measuring techniques.

An example of preliminary results from the radar is shown at the left (click image for full size.) In this case the radar was scanning through a nearby rain shower, stopping to dwell along selected beam directions to obtain wind measurements (left panel). Wind measurements from the dwell direction with the strongest reflectivity are shown as a elevation cross-section in the center panel and compare well with a sounding taken in nearby Denver about half an hour previously (right panel). Analysis of the observations is continuing.

Boundary Layer Turbulence and Fluxes (top)

A recent field project in support of the Advanced Technology Solar Telescope, DASH04, revealed the existence of errors in the measurement of inertial range turbulence by sonic anemometers. The errors are caused by the finite time intervals between the pulses emitted sequentially by the three measurement axes of a sonic anemometer. ATD scientist Tom Horst has investigated and quantified these pulse sequence delay errors, as well as path averaging errors, for the non-orthogonal sonic path geometries used by the CSAT3 and Solent sonic anemometers.

Investigation of Sulfur Chemistry in the Antarctic Troposphere (ISCAT)

Analysis of ISFF measurements taken at the South Pole in the Antarctic summer of 2000 show that NO fluxes emitted from the ice pack are significantly larger than those in the Greenland ice pack, though not by enough to explain the much higher ambient levels of NO at the South Pole. Here, NO is thought to control OH, which determines the rate of oxidation of sulfur that is used to document climatic events. To interpret these results, a method was developed to compute the height of the atmospheric boundary-layer (which contains much of the NO) from tower-based measurements of turbulent velocity spectra. A clear anticorrelation between the NO levels and the boundary-layer height was seen, indicating that boundary-layer structure is critical in controlling NO concentrations.

Left: The vertical Profile and Turbulence Sensors used to calculate fluxes of NO.

Energy Balance Experiment (EBEX)

An international team led by scientists from the University of Bayreuth, Germany, University of Basel, Switzerland, KNMI, the Netherlands, and NCAR/ATD continues to analyze data collected during the surface EBEX in August 2000. This study aims to understand why energy balance closure is difficult, especially over vegetative canopies that also could explain closure problems that have been found for carbon budget studies. Sensor and data handling comparisons have found good agreement between most data subsets and spatial composites have been able to mitigate sampling problems. However, a daytime imbalance of about 15% is still observed. There is some evidence that this could be due to mesoscale heat advection.

Left: The central EBEX tower site during the sensor intercomparison period.

Airflow in Complex Terrain (top)

ATD Scientist Steve Cohn, in association with NCAR's Research Applications Program (RAP), is conducting research into air flows measured around the rugged terrain of Juneau, Alaska. While the eventual goal of this project is development of a turbulence and wind shear alert system for aviation around Juneau, the data collected is also being examined to understand flows in the long, narrow Gastineau Channel (GC) and the high-latitude mountain-valley flow systems of Juneau. The photograph to the left shows the GC, looking to the southeast.

One investigation is into the forcing of strong flows in the GC. Analogous to valley flows, candidate forcing mechanisms are due to thermal gradients, downward momentum transport from the overlying synoptic flow, forced channeling, and pressure driven channeling.

The figure to the left (click for full size) (top frame) shows the wind speed measured at the South Douglas pier within the GC with 1-minute resolution. This is during a 6-day case study period which includes three strong channeled flow events. The overlying synoptic pressure gradient has been found from synoptic analysis maps (every 12 hours). In the upper plot blue dots are the along-channel pressure gradient component, and green dots are the along channel component of the geostrophic wind. It is clear that, at least during this period, winds in the GC are driven by the overlying pressure gradient. They are not well correlated to direct forcing represented by the geostrophic wind component.

Vertical Transport and MiXing (VTMX) Data Analysis (top)

The analysis of VTMX data sets during FY04 has focused on understanding the link between mixing and orographic flows within the stable nocturnal boundary layer. To this end ATD scientists Bill Brown and James Pinto have collaborated with NOAA/ETL and DOE/Pacific Northwest National Laboratories (PNNL) on understanding how nocturnal flow evolves across the Great Salt Lake Basin and how it influences local stability (in press). Analysis of data collected with ATD (sodar, SABL, TAOS, and radiosondes) and PNNL (sonic anemometer) instrumentation revealed that a low-level downvalley jet formed at night about 50% of the time during the VTMX field experiment, which took place in October 2000. The vertical extent and dynamical characteristics (jet max speed, amplitude of wind speed oscillations) of the flow varied substantially from day to day. It was found that several downvalley jet events were characterized by large amplitude / low frequency variations or pulses in the jet strength. These cases were found to have an important feature in common – they all had surface energy budgets that were strongly negative allowing the surface to continue cooling and strengthen the surface-based inversion which often decoupled the surface from the flow aloft, particularly in sheltered areas such as those characterized by the data.

Pulses in the jet strength patterned mixing throughout the basin. At the leading edge of the jet, warm inversion-layer air is turbulently mixed down toward the surface. Behind the jet, mesoscale advection of cold air results in cooling throughout the jet.

Data from a number of sensors characterize the thermodynamic effects of the downvalley jet. Successive soundings obtained before (0427 UTC) and after (0702 UTC) the jet ensued indicate the strong warming in a shallow layer adjacent to the surface and cooling aloft. TAOS data reveal that the warming occurred briefly over a much deeper layer below the jet max in the region where one would expect a significant amount of shear driven turbulence. Data from two surface meteorological stations at different elevations indicate that mixing is delayed at the lower, more sheltered site.

Analysis of the bulk Richardson number and turbulence data from the sonic and sodar reveal that turbulent mixing of warm air down to the lower terrain sites is delayed until the local bulk Richardson number approached the theoretical critical number for the production of turbulence (0.25). That is, the production of turbulence via vertical shear must overcome the strong static stability of the surface-based inversion layer before mixing penetrates down to the surface. Increases in sodar vertical velocity variance prior to reaching the RiB and evidence in the SABL data reveal that waves may precede the vertical mixing by turbulence.

Analysis of research aircraft cloud measurements for assessment of satellite icing retrievals (top)

In conjunction with in-flight icing programs funded by the FAA and NASA, ATD scientists Julie Haggerty and Jothiram Vivekanandan analyzed research aircraft data for assessment of satellite-based cloud retrieval algorithms. Case studies with a variety of icing and non-icing cloud conditions were selected from various field experiments including AIRS-II and WISP04. Results thus far indicate some skill in satellite-based phase retrieval algorithms. Difficulties arise in situations where an overlying cirrus layer obscures supercooled liquid clouds. Partial results are described by Haggerty et al. (2004); additional cases are being examined as appropriate aircraft data are acquired.

Advances in Tropospheric Photochemistry Employing Airborne CH2O Measurements

The APOL group has been actively involved in efforts to advance our understanding of tropospheric photochemistry based upon our high quality ambient formaldehyde (CH2O) measurements acquired during various field campaigns. Last year’s ASR describes one aspect of this activity involving TRACE-P data. APOL is continuing with this endeavor this year with INTEX-NA data. Although it is far too early to formulate a comprehensive story, a preliminary first look at our data reveals a very important finding: namely, the persistence of elevated CH2O mixing ratios at high altitudes during the summer time over the continental United States. Persistent continental thunderstorm activity during the summer months vertically convects polluted boundary layer air to high altitudes where it eventually mixes with cleaner background air in the outflow of clouds. Although this process has been well established, vertical convection of soluble and reactive gases like CH2O has not been well characterized during such events. The flight tracks during the INTEX-NA study, which passed over natural and anthropogenic source regions of the south and mid-west United States, provided an excellent opportunity to study cloud outflow and cloud processing events.

ICE

Ice processes in clouds are poorly understood, especially processes that affect the initial formation and propagation of ice. This lack of understanding results in large uncertainties in numerical modeling work over a wide scope of atmospheric size and time scales, such as the production of precipitation and predicting climate changes. Recent advances in observational tools, laboratory cloud simulation chambers, numerical models, and computer hardware are providing new capabilities to understand and model ice initiation processes.

With support from the NCAR Opportunity Fund, scientists from ATD and MMM organized a community effort to address ice processes in clouds. This past year, a steering committee was formed, and the Ice Initiation Workshop was held in June at NCAR’s Foothills Lab. The workshop ran two days and had invited talks plus presentations by participants. There were 64 attendees from 32 institutions and 5 countries. The ultimate goal of this activity is to develop an NCAR strategic initiative, with NCAR providing scientific leadership to help organize field observations, lab, and modeling studies. Strong participation of the university community is expected, including graduate students. A Scientific Overview Document is being written to supplement proposals by university investigators. The scientific scope, participants, and activities of this project are summarized on the web. Another web page (MMM) summarizes the workshop and has presentations of the talks.

Melt Pond Coverage on Arctic Sea Ice (top)

In a collaborative effort between NCAR, the University of Colorado, and the US Army Cold Regions Research and Engineering Lab, and led by ATD's Mark Tshudi, photo mapping of melt pond coverage on sea ice was undertaken in the Arctic during the summer of 2004 using Aerosondes. Aerosondes are small, long endurance, unmanned aerial vehicles (UAV) that have a 3 m wingspan and can carry a 2.5 kg payload. They are designed to undertake a wide range of operations in a highly flexible and inexpensive mode. The aircraft, developed by a US-Australian consortium, are operated and are undergoing further development by Aerosonde Robotic Aircraft and Aerosonde North America.

Melt ponds have been identified as a key feature in determining the amount of solar insolation absorbed by sea ice, and hence is a primary controller of the melt rate of the ice through the summer. Sea ice models have, to date, crudely parameterized ponds, due in part to a lack of large-scale observations of their temporal and spatial evolution. This NASA-funded study uses observations from the EOS sensor MODIS to estimate pond fraction over a large portion of the Beaufort and Chukchi, by examining several spectral (visible and near-infrared) MODIS bands and deducing melt pond coverage from the known spectral properties of ponds.

The Aerosonde flights dedicated to the melt pond study were necessary to test the validity of the pond coverage estimated using the MODIS data. These flights utilized a downward-looking Olympus C-3030 digital camera, mounted within the Aerosonde, to photograph the sea ice. The digital photos are to be analyzed by the investigators to classify each photo according to the percentage cover of melt ponds, unponded ice, and open water. These estimates are compared to the values retrieved using MODIS for the same area of coverage. To enhance these comparisons, missions were flown with 10 km x 10 km grid patterns, with overlapping (along-track and cross-track) digital photos, which allow for comparison with 400 MODIS pixels (500 m resolution).

The image to the left is a MODIS image of sea ice (white), clouds (shaded in yellow), with an Aerosonde track flown (in red) the same day. Land is dark, with Barrow indicated by the “+”.

Additional missions were designed to examine the evolution of pond coverage over sea ice off the coast of Point Barrow, Alaska. The sea ice in this area of interest was fast ice (i.e. not drifting ice) and served as an area where melt ponds can be observed during formation and their evolution through the summer. The Aerosonde team flew several flights paralleling Point Barrow and overlapping in a pattern that provided contiguous digital camera images of the fast ice from shore to a few km off the coast. These flights were repeated several times during June, providing imagery that will assist investigators in determining how pond fraction changes over this period.

Table of Contents | Director's Message | Executive Summary | ATD Achievements
Education and Outreach | Community Service | Awards | Publications | People | ASR 2004 Home