IWRAP: the Imaging Wind and Rain Airborne Profiler for remote sensing of the ocean and the atmospheric boundary layer within tropical cyclones

IWRAP, the Imaging Wind and Rain Airborne Profiler, is the first high-resolution dual-band airborne Doppler radar designed to study the inner core of tropical cyclones (TCs). IWRAP is currently operated from a National Oceanic and Atmospheric Administration (NOAA) WP-3D aircraft during missions through TCs and severe ocean storms. The system is designed to provide high-resolution, dual-polarized, multi-beam C- and Ku-band reflectivity and Doppler velocity profiles of the atmospheric boundary layer within the inner core precipitation bands of TCs and to study the effects precipitation has on ocean wind scatterometry as it applies to TCs. This dual-wavelength system also provides for the use of differential attenuation techniques to derive the rainfall rate and to characterize the dropsize distribution (DSD) within TCs. This prototype has demonstrated its capability to measure the wind field and the rainfall rate over the range of winds and rain rates usually present in this kind of scenario, and has served as a proof of concept for the design of similar instruments aboard other platforms such as unmanned aerial vehicles (UAV) flying at high altitudes, as well as for spaceborne applications. IWRAP implements a very unique measurement strategy, it profiles simultaneously at four separate incidence angles (approximately 30, 35, 40 and 50 degrees) while conically scanning at 60 RPM. A summary of the principles of operation and the system design of the instrument is given, and examples of IWRAP's unique imaging capabilities are presented and compared against high density sequencies of GPS dropsondes and other radars aboard the aircraft. To our knowledge, the examples that will be presented include the highest-resolution measurements of the boundary layer winds in a hurricane ever obtained