The FORMOSAT-3/COSMIC system is a constellation of 6 LEO micro-satellites. It provides global observation of pressure, temperature, water vapor, refractivity, ionospheric electron density and scintillation for weather and space weather research as well as climate monitoring. Taking advantage of localized (in longitude) satellite orbits during the temporary parking phase, we had conducted two months' IOP campaigns in TIMREX(Terrain Induced Monsoon Rainfall Experiment)period(May 1 to June 30 , 2008). The IOP campaign allows most complete comparison and validation of FORMOSAT-3 GPS Radio Occultation Observations with ground-based observations and dropsonde experiments and other space-based observations in East Asia longitude region.

In this study, the WRF 3DVAR data assimilation with the real time GPS Occultation Observations is utilized to investigate influences of GPS occultation refractivity on the real-time regional weather prediction. The main tasks of this research areF(1) Conduct real time WRF 3DVAR assimilation forecast with FOMOSAT-3 observation data and assess the impact of the GPS data on regional weather prediction. (2). Conduct WRF 3D-VAR update cycle experiments to asses the impact of update cycling on regional weather prediction. (3) Conduct WRF model validation with FORMOSAT-3 IOP campaign observation data. Results from this study show that the assimilation of GPS RO data is likely to have some impact on regional weather prediction through better recover better structure of temperature and moisture field. The assimilation of refractivity data can also lead to a better prediction of typhoon track.