GPS meteorology: Validation and comparisons with ground-based microwave radiometer and mesoscale model for the Italian GPS permanent stations

Ground-based GPS meteorology has been developed during the last decade. Bes ide the GPS traditional application for precise geodesy, the GPS system has proved to be a powerful tool in atmospheric studies, such as climatology a nd meteorology. During 1999, at the Space Geodesy Center (CGS) of the Itali an Space Agency (ASI) an operative and automatic system was developed in or der to produce GPS tropospheric parameters on a daily basis for the Italian GPS permanent stations. In this work the operational processing of the GPS data is described. Moreover, the validation of the GPS tropospheric parame ters through a comparison with other independent GPS solutions as well as i ndependent techniques is presented. The GPS internal validation of zenith t ropospheric delay (ZTD) shows a bias of 5 mm (absolute values) and a standa rd deviation ranging from 4 to 20 mm. For a few stations a comparison is pe rformed between the GPS derived precipitable water vapor (PWV) and both the one computed using the MM5 and the one measured by the water vapor radiome ter (WVR) and radiosondes (RAOB). The agreement between GPS and MM5 is with in the range of 27 mm; for GPS, WVR and RAOB the standard deviation ranges from 0.85 to 1.62 mm. (C) 2001 Elsevier Science Ltd. All rights reserved.