Assimilation of GNSS Radio Occultation Data into Numerical Weather Prediction

Abstract

Today's Numerical Weather Prediction (NWP) systems assimilate meteorological observations from a variety of sources. This information is used operationally to update the analysis of global or regional three-dimensional meteorological fields. The resulting analysis enables then to issue weather forecasts of prime importance for many users. Occultation data collected by refraction of signals from Global Navigation Satellite Systems (GNSS) in the atmospheric limb contain information in temperature and water vapor content. This paper reviews data assimilation techniques, the information contained in GNSS occultation data and how it pertains to the observational needs of today's NWP systems. Recent forecast impact experiments of GNSS occultation data are reviewed, and specific areas for further impact are discussed.