Coincident observations, with QuikSCAT and ASCAT, of the effects of rain-induced sea surface stress during hurricanes Gustav and Ike

The use of satellite scatterometers to probe the winds in and near strong storms and hurricanes is a valuable tool for weather forecasters. The presence of widespread rain in these storms makes the estimates of surface winds from the satellite data problematic. A motivating question here is: "Is there a substantial influence of rain on the air-sea momentum exchange in Hurricanes". Satellite scatterometer measurements were made for Hurricane Gustav (C-Band), which affected New Orleans on September 1 and Hurricane Ike (Ku-band) which impacted the Texas coastline near Houston, on September 13, 2008. The NEXRAD rain reflectivity images (available every 6 minutes) show that there was wide rain coverage throughout these storms. The sustained surface wind estimates from NOAA/ AOML/ HRD show a maximum of 90 kts, and a wide inhomogeneity even within 50 km areas. The broad swath coverage of the NEXRAD radar enables us to select and compare NRCS effects in both rain and non-raining areas. The methodology to be presented here demonstrates how the atmospheric influence can be removed to observe the total surface NRCS.