Application of GPS Radio occultation data in global climate change study

Land,air and ocean temperature,atmospheric water vapor content,and sea level rise are among the key indicators of global climate change as a result of anthropogenic warming.The lack of in situ observations has resulted in significant errors in Numerical Weather Prediction(NWP) models over the polar region,especially over Antarctica and its surrounding ocean.While contemporary studies of atmospheric(lower troposphere) temperature and water vapor variability have been based on NWP models and passive microwave sounders,while quantifications using an accurate and homogeneous global data set have not yet been unavailable.The recently launched constellation of 6-satellite COSMIC satellites in addition to CHAMP,GRACE and SAC-C,provides an opportunity for global atmospheric observations via radio occultation(RO) including water vapor,temperature,and pressure profiles with improved spatial,temporal and vertical resolutions.Our primary scientific objective is to improve and quantify the pressure field modeling over Antarctic for mass balance studies,and to study the feasibility of using RO-derived water vapor and temperature profiles from the constellations of GNSS satellites(COSMIC,CHAMP,SAC-C) for climate change studies.We propose to validate RO retrieved atmospheric observations including refractivity(N),and evaluate 1-D VAR algorithms to optimally estimate pressure,temperature and humidity profiles,focusing on Antarctica and surrounding seas,where air is largely dry with temperature 2500K.We will inter-compare retrieved N from COSMIC satellites during the Intensive Verification Period,and with CHAMP and SAC-C data.The external data products to be used include Automatic Weather Stations in Antarctica,NWPs(ECMWF,NCEP and Polar MM5s),radar altimeter mission(TOPEX,ENVISAT,GFO,JASON) radiometer-measured integrated water vapor and NOAA-AMSU,and other radiometers,OSTIA sea surface temperature,and selected regional GPS-slant range derived water vapor tomography maps.The broader impacts of the study are its direct relevance to climate change studies,improving advanced remote-sensing technologies for weather and space weather forecasting.