A global analysis of tropospheric water vapor obtained from GPS refractivities

We describe our efforts to improve the characterization of the tropospheric water vapor below 500 mb by combining GPS RO refractivities with temperatures from the Atmospheric Infrared Sounder (AIRS) instrument and the European Centre for Medium-Range Weather Forecasts (ECMWF). Inter-comparisons and statistical differences among the GPS-derived, the AIRS, the ECMWF, and radiosonde water vapor profiles will reveal the complementary nature of active and passive sounding techniques. We divide our datasets into three different regions: (a) tropics, (b) mid-latitude, and (c) high-latitude. We repeat the above-mentioned comparisons for each region. Analyzing the t-test statistics and correlation coefficients at each pressure level, we examine the variability and statistical significance among the retrieved water vapor profiles. In particular, we focus on water vapor differences under cloudy conditions, taking advantage of the cloud-penetrating capabilities of GPS RO and radiosonde. Our research results will demonstrate the importance of the GPS RO technique as a data set complementary to radiances and in-situ measurements for climate research.