Hurricane Wind Speed Estimation Using WindSat 6 and 10 GHz Brightness Temperatures

Abstract

Abstract:The realistic and accurate estimation of hurricane intensity is highly desired in many scientific and operational applications. With the advance of passive microwave polarimetry, an alternative opportunity for retrieving wind speed in hurricanes has become available. A wind speed retrieval algorithm for wind speeds above 20 m/s in hurricanes has been developed by using the 6.8 and 10.7 GHz vertically and horizontally polarized brightness temperatures of WindSat. The WindSat measurements for 15 category 4 and category 5 hurricanes from 2003 to 2010 and the corresponding H*wind analysis data are used to develop and validate the retrieval model. In addition, the retrieved wind speeds are also compared to the Remote Sensing Systems (RSS) global all-weather product and stepped-frequency microwave radiometer (SFMR) measurements. The statistical results show that the mean bias and the overall root-mean-square (RMS) difference of the retrieved wind speeds with respect to the H*wind analysis data are 0.04 and 2.75 m/s, respectively, which provides an encouraging result for retrieving hurricane wind speeds over the ocean surface. The retrieved wind speeds show good agreement with the SFMR measurements. Two case studies demonstrate that the mean bias and RMS difference are 0.79 m/s and 1.79 m/s for hurricane Rita-1 and 0.63 m/s and 2.38 m/s for hurricane Rita-2, respectively. In general, the wind speed retrieval accuracy of the new model in hurricanes ranges from 2.0 m/s in light rain to 3.9 m/s in heavy rain.

A New Generation of Tropical Cyclone Size Measurements from Space

“…While algorithms have been developed that are able to measure ocean surface wind speeds with an accuracy of ~2 m s −1 , in rain-free conditions [e.g., see Bettenhausen et al (2006) and discussions in Meissner and Wentz (2009)], unfortunately, they break down completely as soon as light rain is present. For accurate retrievals of wind speeds when precipitation is present it is essential to use different frequencies, whose spectral signatures make it possible to find X-and C-band channel combinations that yield brightness temperature with sufficient sensitivity to wind speed and low sensitivity to rain (Shibata 2006;Yueh 2008;Meissner and Wentz 2009;El-Nimri et al 2010;Saitoh and Shibata 2010;Mai et al 2016;Zhang et al 2016). This multifrequency channel combination principle also led to the development of the SFMR instrument (Harrington 1980), which measures the brightness temperature of the ocean surface using six distinct close-by C-band frequencies, which permit the simultaneous retrieval of both rain rate and surface wind speed.…”

Comparison of Wind Speeds from Spaceborne Microwave Radiometers with In Situ Observations and ECMWF Data over the Global Ocean

“…This tool can provide scientists and forecasters with vital information for understanding and studying global weather and climate change. Microwave radiometers have long been used to measure ocean surface winds [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. The first Special Sensor Microwave Imager (SSM/I) onboard Defense Meteorological Satellite Program (DMSP) was launched in July 1987, making it possible to estimate global ocean surface winds from a spaceborne passive microwave instrument.…”

Microwave Satellite Systems for Hydrological Monitoring

“…Большинство радиометров космического базирования являются представителями однолучевых радиометрических систем с механическим пространственным сканированием луча в режиме конического вращения [5][6][7][8][9]. Сканирование ведется с помощью вращающегося параболического рефлектора, вблизи фокуса которого расположен набор рупорных облучателей, отвечающих за прием сигнала в нескольких частотных каналах раздельно на горизонтальной и вертикальной поляризациях.…”

“…Сканирование ведется с помощью вращающегося параболического рефлектора, вблизи фокуса которого расположен набор рупорных облучателей, отвечающих за прием сигнала в нескольких частотных каналах раздельно на горизонтальной и вертикальной поляризациях. В отдельных системах реализована схема измерения полного поляризационного набора показателей потока излучения [7][8][9][10]. Сканирование выполняется под некоторым фиксированным углом к надиру, обеспечивая постоянный угол визирования поверхности (угол встречи луча с поверхностью), обычно из диапазона от 50° до 65° по отношению к местному зениту.…”