MONITORING PRECIPITABLE WATER AND SURFACE WIND OVER THE GULF OF MEXICO FROM MICROWAVE AND VAS SATELLITE IMAGERY

Spatial and temporal changes of atmospheric water vapor and surface wind speeds are investigated for a period following an intrusion of cold continental air over the Gulf of Mexico, during the Gulf of Mexico Experiment (GUFMEX) in March 1988. Microwave and infrared satellite measurements from the Special Sensor Microwave/Imager (SSM/I) instrument aboard the Defense Meteorological Satellite Project (DMSP) F8 satellite and from the GOES VISSR Atmospheric Sounder (VAS) are used to augment the sparse coverage of rawinsonde sites and surface reports in the vicinity of the Gulf of Mexico. Total precipitable water is derived from both instruments and from rawinsonde measurements at coastal locations and auxiliary sites on ships and platforms over the Gulf. Accuracies of the precipitable water derived from SSM/I and GOES are comparable, though microwave data provide more uniform coverage, when they are available, than VAS since they are relatively free from contamination by most clouds. Also, the moisture fields derived from microwave data appear to be less noisy than those derived from the infrared. To illustrate possible use of satellite data in the forecast office, moisture fields from both SSM/I and VAS are blended together into imagery, which are compared to analyses from an operational model. Surface wind speeds are also obtained from the microwave data and are compared to the surface observations. Analyses from satellite data appear to add considerable information to the moisture and wind analysis over the Gulf of Mexico and should help in forecasting moisture changes, particularly moisture return near the surrounding coastal areas.