Upper Air Temperature and Circulation Climatologies from GPS Radio Occultation Measurements for Climate Process Studies and Model Evaluation

Abstract:

GPS radio occultation (RO) measurements are known to yield highly accurate temperature and geopotential height in the upper troposphere and lower stratosphere (UTLS) with 200 m vertical resolution in all-weather conditions. With over twelve years (2001-present) of continuous GPS RO measurements now available from CHAMP, COSMIC, and other missions, the dataset has become increasingly valuable in the study of upper air climate trend, variability, and processes. In this presentation, we will describe our approach towards the generation of global monthly gridded data products that include temperature, geopotential height, and geostrophic wind in the UTLS. To interpolate or map the irregularly sampled RO data into a 2D grid, a Bayesian method with spherical harmonic basis functions is implemented. Furthermore, we will quantify the measurement and sampling uncertainty associated with the monthly gridded data. Applications of the dataset in the variability of the tropical belt and CMIP5 model evaluation will be presented. In addition, we will discuss recent progress in reducing systematic retrieval errors as well as efforts to extend the current data record rigorously to the GPS/MET era (1995-1997).