The NOAA Earth System Research Laboratory (ESRL) has been comparing GOES water vapor products with ground-based global positioning system (GPS) integrated water vapor estimates since 2002 (Birkenheuer and Gutman, 2005). The purpose of this work has been to assess GOES total precipitable water (TPW) retrieval performance at both synoptic and asynoptic times, assess seasonal-interannual changes in TPW retrieval performance, and develop strategies to make GOES TPW estimates more useful to NOAA forecasters and modelers. We have observed a consistent moist bias in GOES East, and no significant systematic errors in GOES West with respect to GPS. To deal with the GOES East problem, we have developed an error-correction strategy that brings GOES East measurements into close agreement with GOES West and GPS TPW over CONUS. Using MODIS data as a proxy for GOES-R ABI observations, we have started to make routine comparisons of simulated GOES-R ABI measurements with GPS to assess the relative performance of this anticipated observing system with respect to GOES 9-13. Our initial conclusion is that the simulated ABI retrievals over the Eastern U.S. are in better agreement with GPS, but they tend to be moist biased in the Western U.S. compared with the current GOES West data. The need for an ABI TPW correction will be explored.
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