Hurricane Wind Retrievals Using the SeaWinds Scatterometer on QuikSCAT

Abstract

Meteorologists require reliable real-time measurements of tropical cyclone (TC) conditions to issue hurricane forecasts and advisories. The models they utilize assimilate many sources of data including airborne and spaceborne surface wind estimates. One instrument that has the potential for operational use is the SeaWinds Scatterometer on QuikSCAT. Unfortunately, the adverse effects of rain on the scatterometer signal make these measurements unreliable. Intense rain volumes can drown out radar echo with a combination of attenuation and high backscatter, while the standard resolution of wind measurements tends to wash out high wind retrievals. Furthermore, traditional geophysical model functions (GMF), which relate wind speed and direction with radar backscatter (sigma-0), have not been tuned for the high wind conditions of storms because sampling of these events is poor. Thus, scatterometers tend to underestimate TC winds. By utilizing a combined active/passive retrieval algorithm developed specifically for TCs, we are able to simultaneously retrieve wind speed and rain rates using the SeaWinds Scatterometer. Unreliable wind measurements are flagged based on rain estimates. To certify that wind retrievals are ready for operational use, wind speeds are compared with H*Wind wind fields developed by the Hurricane Research Division of NOAA.