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CHAMP temperature and humidity profile over the South Atlantic (0.5 °W; 53.2°S) on February 11, 2001, 19:44 UTC, compared with data from the European Centre for Medium-Range Weather Forecasts (ECMWF) and the U.S. National Centers for Environmental Prediction (NCEP).
The profiles of temperature and specific humidity shown in the figures above were observed by CHAMP over the Southern Atlantic (53°S,0.3°W) on February 11, 2001, 19:44 UTC, during the first test of the onboard occultation software of the BlackJack GPS receiver (JPL). Operational meteorological analysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) and the US National Centers for Environmental Prediction (NCEP), interpolated onto the occultations location, are shown for comparison.
Similar to the first CHAMP profile taken over Antarctica 11 minutes earlier, the CHAMP sounding reaches close to the ground and provides high quality data on altitudes above 1 - 1.5 km, i.e. (in this case) above the maritime boundary layer. Also noteworthy is the well resolved temperature structure of the tropopause, similar to the one obtained from the first CHAMP temperature profile.
Note that the temperature profile shown has been calculated under the assumption of a dry atmosphere; it is indeed the deviation from ECMWF meteorological analyses that has been used to calculate humidity. Also note that the raw GPS data has been slightly smoothed in the vertical in order to take account for the limited vertical resolution of the meteorological analyses.
Temperature and humidity profile were calculated by the GFZ radio occultation group at GFZ Potsdam using the CHAMP GPS high rate occultation data, GFZ precise orbit data for CHAMP and GPS satellites, and data from the CHAMP high rate and low latency GPS ground station network operated jointly by GFZ and JPL. ECMWF data was provided by the German Weather Service DWD via the Stratospheric Research Group at the Freie Universität, Berlin. NCEP data was provided by the Climate Prediction Center CPC, Camp Springs.
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