Research results from Antarctic automatic weather stations

Automatic weather station (AWS) units have been deployed in Antarctica since 1980 by the U.S. Antarctic Research Program. As of June 1987, 25 AWS units are operating in Antarctica in support of meteorological research. The AWS units measure air temperature, wind speed, and wind direction at a nominal height of 3 m above the surface and air pressure at the height of the electronics enclosure. Some AWS units measure relative humidity at 3 m and air temperature difference between 3 m and 0.5 m above the surface. Three to five values for each sensor are updated at 10-min intervals and transmitted at 200-s intervals to data collection systems on the NOAA series of polar-orbiting satellites. The AWS units in Antarctica are sited to support research on katabatic winds, barrier winds, surface heat fluxes, and climate. Results from the katabatic wind experiment along a line upslope from the Adelie Coast show that the katabatic wind is stronger in winter than in summer and is strongest inland from the coast. The potential temperature difference from the south pole to the Adelie Coast has the largest negative value in winter, supporting the stronger katabatic winds. The katabatic flow down the glaciers of the Transantarctic Mountains to the Ross Ice Shelf requires synoptic support because the potential temperatures on the Ross Ice Shelf are lower than at higher elevations such as the south pole. Data from AWS sites on the Ross Ice Shelf along the Transantarctic Mountains generally have southerly monthly resultant wind directions along the mountains. Ross Island with its 3000-m-high volcanoes deflects the southerly wind flow, resulting in an easterly wind direction at McMurdo Station. AWS units equipped to measure vertical air temperature difference and relative humidity provide estimates of the latent and sensible heat flux on the Ross Ice Shelf. Generally, the sensible heat flux is negative, and the latent heat flux is small. The collection of the AWS data by a local user terminal at McMurdo Station makes possible the use of the AWS data to support air operations.