Climate studies

Antarctic Meteorological Research Center. Charles Stearns and John T. Young, University of Wisconsin. The Antarctic Meteorological Research Center (AMRC), one of three research centers in the Crary Science and Engineering Technology Center at McMurdo Station, is a resource for meteorological research and a test bed for improving operational synoptic forecasting. The Man-Computer Interactive Data Access System (McIDAS), a versatile computer-based system for organizing, manipulating, and integrating antarctic environmental data, forms the basis of AMRC. McIDAS not only captures the flow of meteorological information from polar-orbiting satellites, automatic weather stations (AWS), operational station synoptic observations, and research project efforts, but it also receives environmental data products, such as weather forecasts, from outside Antarctica and serves as a repository for existing archived databases. Developed at the University of Wisconsin in the mid-1970s, McIDAS ingests meteorological data from various sources, standard synoptic observations, radiosonde profiles, satellite-based visible and infrared imagery, atmospheric profiles inverted from multispectral scanning sensors, and nonstandard sources such as total ozone mapping spectrometer data, synthetic aperture radar sea-ice information, and the AWS network observations. The system automatically registers, calibrates, and locates (by geographical coordinates) the ingested information and allows a user at a work station to manipulate the database. The manipulations, which include sectorization, false color, enhancements, brightness stretching, overlays, and looping, are quite definitely keyed to synoptic meteorological research and weather forecasting. The antarctic system is based primarily on data streams provided by polar orbiters (AVHRR/ HRPT and DMSP), because the angles of sight for geostationary satellites are extremely low. The full use of McIDAS capabilities to produce meteorological data products for forecasting and research will include data-transfer and communications capability to, for example, the Australian Bureau of Meteorology, the University of Wisconsin Space Science and Engineering Center, the Fleet Numerical Oceanography Center in Monterey, and the European Center for Medium Range Weather Forecasts in Reading, United Kingdom. (S-202)

Antarctic halos and ice crystals. Walter Tape, University of Alaska. Our project is an experimental and theoretical study of ice crystals in the antarctic atmosphere and the halos that they produce. For reasons that are not currently known, the antarctic interior experiences more frequent and better developed halos than any other location on Earth. Our objectives are to observe natural halos at Amundsen­Scott South Pole Station and to sample ice crystals to validate computer models of light refraction and reflection in ice crystals. Such models have the potential for the remote sensing of atmospheric conditions. Controlled experiments, such as seeding the atmosphere with dry ice, will produce artificially generated but simple and well-formed single-species crystals. Our research provides a unique mechanism for examining the crystal growth and evolution process in the natural atmosphere. By observing halos through polarizing filters, we will also be able to examine the atmospheric ice-crystal orientation, shape, and size. The results of our project will advance our understanding of why well-formed ice crystals grow in the antarctic atmosphere but are not generally observed elsewhere. (S-208)

Chlorine- and bromine-containing trace gases in Antarctica. R.A. Rasmussen, Oregon Graduate Institute for Science and Technology. We are collecting air samples year-round at Palmer Station to investigate seasonal trends in trace-gas concentrations. The samples are analyzed in our laboratories for a number of trace components, especially chlorine-and bromine-containing gases. These trace constituents, which come from both natural and human sources, can alter the Earth's climate. They have even been implicated in the chemical processes that contribute to the austral spring depletion of the ozone layer over Antarctica. Our work will contribute to a better understanding of the buildup of trace constituents, particularly those of high-latitude marine origin. (S-254)

South Pole monitoring for climate change. AmundsenñScott South Pole Station: David Hofman, Climate Monitoring and Diagnostics Laboratory; Palmer Station: James T. Peterson, Environmental Research Laboratories, National Oceanic and Atmospheric Administration. The National Oceanic and Atmospheric Administration (NOAA) Climate Monitoring and Diagnostics Laboratory team will continue long-term measurements of trace atmospheric constituents that influence climate. Four scientists will work at the AmundsenñScott South Pole Station observatory during the austral summer, and two NOAA personnel will stay over the winter to measure carbon dioxide, water vapor, surface and stratospheric ozone, wind, pressure, air and snow temperature, and atmospheric moisture and other trace constituents from the station's clean-air facility. These measurements are part of NOAA's effort to determine and assess the long-term buildup of global pollutants in the atmosphere. The measurements will be used for time-series analyses of multiyear data records that focus on stratospheric ozone depletion, transantarctic transport and deposition, interplay of the trace gases and aerosols with solar and terrestrial radiation fluxes on the polar plateau, the magnitude of seasonal and temporal variations in greenhouse gases, and the development of polar stratospheric clouds over Antarctica. Other objectives of our research are to determine the rate at which concentrations of these atmospheric constituents change and to examine their sources, sinks, and budgets. Working with climate modelers and diagnosticians, we will use these data to determine how the rate of change of these parameters affects climate, particularly when the data are included in climate model studies. In support of this project, Palmer Station personnel also will collect carbon dioxide samples. (S-257A and S-257C)

Operation of an aerosol sampling system at Palmer Station. Gail dePlannque and Colin G. Sanderson, Environmental Measurements Laboratory, U.S. Department of Energy. In March 1990, a team from the U.S. Department of Energy, Environmental Measurements Laboratory (EML) in New York City, installed a high-volume aerosol sampler, a gamma-ray spectrometer, and a satellite data transmission system at Palmer Station. This installation is part of EML's Remote Atmospheric Measurements Program, which is an extension of its worldwide surface air-sampling program. The system transmits data through the National Oceanic and Atmospheric Administration's ARGOS satellite system. The sampling station at Palmer provides significant input for EML's global database. (S-275)

Antarctic automatic weather stations: Operation and research. Charles Stearns, University of Wisconsin at Madison. Approximately 50 automatic weather stations measuring surface pressure, air temperature, wind speed and direction, and at some sites, humidity are located in remote areas of Antarctica. The data are transmitted to polar-orbiting satellites of the National Oceanic and Atmospheric Administration series and are rebroadcast for reception at McMurdo and Palmer Stations in Antarctica. The data from the weather stations are used to study the barrier wind along the Transantarctic Mountains; vertical motion and sensible and latent heat flux from the Ross Ice Shelf; warm west winds flowing from the Beardmore and Byrd Glaciers; katabatic flow on the Adélie Coast, Antarctica; and mesoscale systems around the South Pole. The data are used to establish long-term climate records at selected sites. Starting in the 1994­1995 field season, the data were used to study the meteorology of the west antarctic/Siple Coast region. During the 1995ñ1996 field season, automatic weather stations were installed in support of future ice coring; the first such location will be at Siple Dome. Data from the automatic weather stations are also used in support of aircraft operations in Antarctica. The data are available from the University of Wisconsin. (S-283)