Comparison of Water Vapor Measurements from GPS Atmospheric Remote Sensing Techniques

In this study, we compare precipitable water vapor (PWV) values from two different observing techniques over the Caribbean Sea, Gulf of Mexico, and U.S. regions, including ground-based GPS water vapor sensing and COSMIC radio occultation (RO) measurements, as well as global analyses from NCEP and ECMWF models. The PWV values estimated by ground-based GPS receivers tend to have a slight dry bias for low PWV values and a slight wet bias for higher PWV values, when compared with space-based techniques. This may be a consequence of missing low altitude data from RO in areas where the water vapor is concentrated, locations of the RO soundings with respect to ground-based stations, or simply the difference of these two measurement techniques. A student T-test application gives a retrieved t-value of 2.35, which is larger than the sample's critical value, 1.96. This means there is a significant difference between both GPS techniques datasets with a 0.01{\%} chance of observing a difference as large as it was observed in other random samples.