Comparing wind speed retrievals from GPS reflectometry with SFMR surface wind speeds in Huricane Ike (2008)

Recently, a compact system, able to record raw GPS intermediate frequency (IF) samples has been designed and tested by the research group at the CU/Aerospace Engineering Sciences Department. Such an approach provides the most fundamental measurement, enabling the most advanced and complete post-processing, with data volumes on the order of 1GB/minute. In 2008 this system was flying on board the NOAA WP-3D aircraft which collected research-mission data on Hurricane Ike. During two flights there was collected about 800 GB of raw data for flight lags that transverse the hurricane eye and away from it. After the flights the correlation waveforms for both direct and reflected signals were retrieved from the raw data for all available satellites and sea surface roughness estimates were produced. Those retrievals were compared with the Step Frequency Microwave Radiometer (SFMR) measurements of the surface wind speed. As expected, the data show a high sensitivity of the GPS bistatic radar signals to ocean surface roughness. However, the system of swells generated by various parts of the hurricane complicates the picture and makes the problem of wind retrieval non-trivial.