Instrument: Radiosonde Vaisala RS80-GPS
Vaisala RS80-GPS radiosondes carried aloft by helium balloons measure atmospheric temperature, humidity, wind speed and direction. The GPS receiver of the GPS-radiosonde measures a shift in Doppler frequencies using a codeless detection and measurement technique. The measured Doppler shifts are a combination of satellite and radiosonde motion and contain the pertinent information for wind speed and
direction computation. Doppler frequency measurements of up to 8 satellites are sent to the ground equipment using a low bandwidth (1200 baud) digital link. New independent GPS Doppler measurements from the GPS-sonde are provided every 0.5 seconds for up to 8 channels with 24-bit resolution. The ground equipment computes the wind
speed and direction using the differential GPS concept. For more information see www.hobeco.net/pdf/RS80_GPS.pdf.
Radiosondes
Profiles of atmospheric temperature, humidity, wind speed and direction were measured
using Vaisala RS80-GPS radiosondes carried aloft by helium balloons. A list of radiosonde
launches is given as the data file list. The data are transmitted from the sonde to a
shipboard receiver and these are stored at 2-s intervals by computer. This sampling
gives good height resolution in the atmospheric boundary layer, which is under the direct
influence of the fluxes through the sea surface. The radiosondes were generally launched
to coincide with the overpasses of the NASA Aqua earth observation satellite, as the
atmospheric profiles derived from the radiosondes can be used to validate satellite
retrievals of atmospheric temperature and humidity distributions.