Remote Sensing of Tropical Cyclones: Applications from Microwave Radiometry and Global Navigation Satellite System Reflectometry

[摘要] Tropical cyclones (TCs) are important to observe, especially over the course of their lifetimes, most of which is spent over the ocean. Very few in situ observations are available. Remote sensing has afforded researchers and forecasters the ability to observe and understand TCs better. Every remote sensing platform used to observe TCs has benefits and disadvantages. Some remote sensing instruments are more sensitive to clouds, precipitation, and other atmospheric constituents. Some remote sensing instruments are insensitive to the atmosphere, which allows for unobstructed observations of the ocean surface. Observations of the ocean surface, either of surface roughness or emission can be used to estimate ocean surface wind speed. Estimates of surface wind speed can help determine the intensity, structure, and destructive potential of TCs. While there are many methods by which TCs are observed, this thesis focuses on two main types of remote sensing techniques: passive microwave radiometry and Global Navigation Satellite System reflectometry (GNSS-R).First, we develop and apply a rain rate and ocean surface wind speed retrieval algorithm for the Hurricane Imaging Radiometer (HIRAD). HIRAD, an airborne passive microwave radiometer, operates at C-band frequencies, and is sensitive to rain absorption and emission, as well as ocean surface emission. Motivated by the unique observing geometry and high gradient rain scenes that HIRAD typically observes, a more robust rain rate and wind speed retrieval algorithm is developed. HIRAD’s observing geometry must be accounted for in the forward model and retrieval algorithm, if high rain gradients are to be estimated from HIRAD’s observations, with the ultimate goal of improving surface wind speed estimation.Lastly, TC science data products are developed for the Cyclone GlobalNavigation Satellite System (CYGNSS). The CYGNSS constellation employsGNSS-R techniques to estimate ocean surface wind speed in all precipitatingconditions. From inputs of CYGNSS level-2 wind speed observations and thestorm center location, a variety of products are created: integrated kinetic energy,wind radii, radius of maximum wind speed, and maximum wind speed. Theseproducts provide wind structure and intensity information—valuable for situationalawareness and science applications.

[发布机构] University of Michigan

[效力级别] tropical cyclones

[关键词] remote sensing;tropical cyclones;passive microwave radiometry;Global Navigation Satellite System reflectometry;Hurricane Imaging Radiometer (HIRAD);Cyclone Global Navigation Satellite System (CYGNSS);Atmospheric;Oceanic and Space Sciences;Science;Atmospheric, Oceanic & Space Science