Remote sensing of the ocean and the atmospheric boundary layer within tropical cyclones.

摘要

This dissertation presents the Imaging Wind and Rain Airborne Profiler (IWRAP), the first high-resolution dual-band airborne Doppler radar designed to study the inner core of Tropical Cyclones (TCs). IWRAP is usually 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 C- and Ku-band reflectivity and Doppler velocity profiles of the atmospheric boundary layer (ABL) within the inner core precipitation bands of TCs and to study the effects precipitation has on ocean wind scatterometry as it applies to TCs. A summary of the principles of operation and the design of the instrument is given, with an emphasis on the unique digital receiver. Airborne ocean backscatter measurements at C- and Ku-band wavelengths and HH and VV polarizations obtained in moderate to very high wind speed conditions (25--65 m·s-1) are presented. The differences between these measurements and current geophysical model functions (GMFs) are reported. The impact of these results on satellite-based scatterometry is discussed, and their application is illustrated through the reprocessing of QuikSCAT passes with the new GMFs. The use of dual wavelength techniques to determine differential attenuation from IWRAP's dual band reflectivity measurements, as well as to derive rainfall rates and drop-size distribution parameters is also addressed. In addition, results on the use of the radar Doppler velocity measurements to derive the three-dimensional (north, east and vertical) components of the ABL winds within rainbands of TCs are presented. Validation of these results is performed by comparison against other available datasets. IWRAP's unique imaging capability provides, to our knowledge, the highest-resolution measurements of the ABL winds of a hurricane ever obtained.