GPS PW assimilation into MM5 with the nudging technique

Abstract We use a sub-set of European GPS network, equipped with surface meteorological sensors, to evaluate the impact of GPS precipitable water (PW) on the numerical weather prediction (NWP) model. GPS PW are assimilated into the PSU/NCAR nonhydrostatic model MM5 using both the Nudging technique and the Objective Analysis. The selected GPS network is made by six stations: Cagliari, Graz, LAquila, Matera, Wettzell and Zimmerwald. In this work we test the whole processing from GPS data reduction to GPS PW assimilation in order to critically evaluate GPS PW impact on the weather forecast.