The Antarctic continent is 97% covered with ice with an average elevation of 2300 meters and an average annual temperature of -35 degrees C, making Antarctica the highest and coldest continent on Earth. Maintaining occupied sites for collecting meteorological observations is expensive, and the locations may not be appropriate for the collection of meaningful meteorological data. The capabilities of an automatic weather station allow for the retrieval of important weather information without having to have a person on duty at each site. These stations have proven to be an invaluable resource for researchers, forecasters, as well as the general public regarding gathering important meteorological information about the Antarctic.
At the end of the 2003-2004 field season, just under sixty stations were operational in the Antarctic. Three new sites, Wanderer, Vito, and Emilie were added during the 2003-2004 field season. As of 2004, Amundsen-Scott Station at the South Pole was the only year round interior station in Antarctica with personnel. The remaining year around stations are located on the Antarctic Coast at sites that can be reached by ship. The coast of West Antarctica from 180 degrees east to 75 degrees west longitude does not have one station with year around observations.
The development of low power computer components in the 1970s and the ARGOS DCS on the NOAA series of polar-orbiting satellites made possible the development of low-power AWS units capable of operating in the extreme climate of Antarctica. These components allow for longer operational use between visitation of the sites.
The AWS units are grouped together based on area and are usually related to a single meteorological experiment. The data are not always continuous, as the units occasionally stop and cannot be repaired or replaced until the next field season. Occasionally, a unit may stop for a month or two then start up on its own.
The operations of the AWS unit are controlled by a small microcomputer operating at 819kH using a read-only-memory (ROM) of 2024 x 8 with 256 x 8 random access memory (RAM). The microcomputer updates the data at a nominal 10 minute interval and at 200 second intervals transmits 256 bits of data. The transmissions are in the blind and if the NOAA satellite is within line of site of the AWS unit, the transmission will be received and stored by the ARGOS DCS. The satellite frequently will be in the line of sight for as much as 15 minutes and will receive two different data transmissions. The orbital period of the NOAA satellites is approximately 102 minutes, and two satellites are in operation at one time.
The AWS data are updated at a nominal 10 minute interval. The pressure, temperature, wind speed, and wind direction are stored for the last update. Then, the difference between successive readings of the pressure and temperature are stored for the previous four readings ten minutes apart. The previous four updates of the wind speed and wind direction are stored and entered into the data transmission.
The present and two previous values 20 minutes apart of relative humidity and vertical temperature difference are also stored in the transmission. If there is an update during the satellite passage, and if there is about 50 minutes between the passages of the two satellites, this is sufficient to provide data from a station every 10 minutes for 24 hours. The AWS unit is powered by six to twelve 40 ampere-hour 12 volt gel-cell batteries charged by one or two 10 Watt solar panels. At the South Pole, 12 batteries and two solar panels are sufficient to operate the AWS unit through the year, while six batteries and one solar panel are adequate on the Ross Ice Shelf. Several of the AWS units have operated on the same batteries and solar panel for 6 to 10 years.
To see pictures of the different sensors, please visit here.
Here is a sample schematic of a basic AWS unit.
