Asymmetrical wind and surface mean square slope correlation observed in Hurricane Ike

This paper analyzes and compares multiple techniques for estimating the mean square slope (MSS) of surface waves during Hurricane Ike in the Gulf of Mexico and studies the correlation of these estimates with co-located independent surface wind measurements. The measurements used in this analysis include a GPS reflections instrument, a Scanning Frequency Microwave Radiometer (SFMR), a Wide Swath Radar Altimeter (WSRA), and HWinds modeled wind fields. These data sets were used to study the correlation between the near-surface wind and waves during Hurricane Ike in 2008. The GPS-R, SFMR and WSRA instruments recorded temporally and spatially coincident data during two passes over the hurricane eye. This paper estimates the ocean surface waves mean square slope using GPS-R for two eye transects using: a) a least squares model fitting technique; b) a model-based waveform width method; and c) a model-based integration of the area around the reflection peak. Subsequently, the correlation between the GPS-R MSS estimates and the SFMR wind speed estimates are compared to reveal regions of high and low wind/wave correlation. Subsequently, the correlation of MSS estimates from the higher frequency WSRA instrument and SFMR wind estimates are calculated. It has been found that (generally) the wind and wave correlation is significantly better on the western side of the storm during both hurricane eye transects. A relationship between wind and waves was then derived from the GPS-R and SFMR data and is compared to existing wind/wave models, including the results obtained by Katzberg et al and with the Elfouhaily et al theoretical model.