Real-time airborne radar wind-profiling algorithm for the Integrated Wind and Rain Airborne Profiler

The Integrated Wind and Rain Airborne Profiler (IWRAP) is a dual-frequency dual-polarization radar developed by the Microwave Remote Sensing Laboratory at the University of Massachusetts that is installed routinely on the NOAA WP-3D research aircraft. Primarily designed to study the signature of the ocean surface under wind forcing, it has recently been modified to enable profiling through precipitation through the use of pulse-compression. The radar scans conically below the aircraft with a scan rate of 60 rpm, thereby enabling VAD wind retrievals at a 1 s update rate.

Without compensation, wind retrievals at altitudes below approximately 300 m are subject to contamination by scattering from the sea surface through antenna sidelobes, inducing a negative bias in lower boundary layer winds. We have implemented an algorithm that is amenable to real-time implementation that suppresses this surface echo to enable improved retrieval of lower BL winds. The algorithm includes an adaptive notch-filter that rejects the surface echo, enabling fast covariance-based estimation of the precipitation echo Doppler shift. The entire process is performed in the time-domain.

We demonstrate the algorithm's performance with data collected during the 2008 hurricane season. Real-time implementation for future hurricane flights is discussed.