Devised Scheme To Correct GOES Bias In GOES Operational Total Precipitable Water Products

Abstract

The National Environmental Satellite Data and Information Service (NESDIS) Geostationary Observational Environmental Satellite (GOES)-derived, total precipitable water (TPW) vapor product is routinely produced at NESDIS for Advanced Weather Interactive Processing System (AWIPS) users, primarily for National Weather Service (NWS) forecast offices. Global Positioning System (GPS) signal delay due to atmospheric water vapor has been shown to provide accurate, real-time, measurement of TPW. Until GPS data came on the scene, there had been no way to validate GOES product data at asynoptic times (other than the occasional field experiment or limited regions such as the ARM CART sites), and therefore routine rawinsonde (RAOB) data have the largest influence on calibration, and these are constrained to fundamental synoptic times and frequency (every 12 hours). This paper examines asynoptic satellite product performance and explores corrections to GOES product differences based on GPS measurements. The derived correction scheme is useful not only for applying to satellite data before use, but for studying error characterization as well. It becomes apparent that GOES 12 data error characteristics, measuring the eastern continental U.S. (CONUS) are also present in GOES 10, even though GOES 10 data are far drier (measuring the western CONUS) and from a completely different set of optics and satellite acquisition systems. This suggests that the observed product bias may be due to elements common to both satellite data products, e.g., model first guess, cloud clearing, tuning to only synoptic data, or some other unknown issue. The development of the satellite product correction algorithm is detailed and coefficients for correction to GOES 12 and GOES 10 product data are presented.