TEST AND STUDY OF THE EARTH-BASED GPS TECHNIQUE FOR REMOTE SENSING OF ATMOSPHERIC PRECIPITABLE WATER

The deviation of AN (Askne and Nordius) model for calculating PW value has been analyzed theoretically and the conclusion drawn from the theoretical analysis has been confirmed by the results from the sounding test. Through the derivation, a new precipitable Water (PW) calculation model has been established and the calculated results are well consists with the PW values obtained by the sounding method. In 1998, a "GPS Storm Observation Test" was car ried out. It has been discovered from the test results that the high-value time interval of PW generally has an increasing period before the rainfall and a decreasing period in the process when the rainfall is ended; before the occurrence of a sudden storm event, unexpected large-scale increase of PW often occurs; before the occurrence of a large storm event, there is a very clear pregnancy period lasting for a long time.