A PRELIMINARY STUDY ON THE QUALITY CONTROL METHOD FOR GUANGDONG GPS/PWV DATA AND ITS EFFECTS ON PRECIPITATION FORECASTS IN ITS ANNUALLY FIRST RAINING SEASON

We first analyzed GPS precipitable water vapor （GPS/PWV） available from a ground-based GPS observationnetwork in Guangdong from 1 August 2009 to 27 August 2012 and then developed a method of quality control beforeGPS/PWV data is assimilated into the GRAPES 3DVAR system. This method can reject the outliers effectively. Afterestablishing the criterion for quality control, we did three numerical experiments to investigate the impact on theprecipitation forecast with and without the quality-controlled GPS/PWV data before they are assimilated into the system.In the numerical experiments, two precipitation cases （on 6 to 7 May, 2010 and 27 to 28 April, 2012 respectively） thatoccurred in the annually first raining season of Guangdong were selected. The results indicated that after quality control,only the GPS/PWV data that deviates little from the NCEP/PWV data can be assimilated into the system, has reasonableadjustment of the initial water vapor above Guangdong, and eventually improves the intensity and location of 24-hprecipitation forecast significantly.