Hurricane Wind Retrieval

Passive microwave radiometers have provided Earth observations from orbit for decades, and many retrieval algorithms utilize them for land surface, sea state and atmospheric modeling. Oceanic wind vector retrievals in particular are well characterized for the most prevalent conditions, with light precipitation at most and calm to moderate surface winds (below 25 m/s or 55 mph). However, extreme weather events such as tropical cyclones (TC) present conditions beyond these algorithms’ valid ranges and render them unable to provide wind retrievals. Wind estimates under these conditions are important for hurricane forecasting, and programs such as the Joint Center for Satellite Data Assimilation (JCSDA) have made improving such numerical weather predictions a priority. Developing a robust retrieval algorithm for ocean winds in TCs and other extreme weather events will provide more input for data assimilation systems related to hurricane predictions and improve the overall quality of the forecasts.

The goal of this project is to develop a robust ocean surface wind vector retrieval algorithm under extreme weather events. Atmospheric effects are generally negligible or at worst easily accounted for over most ocean data, but the heavy precipitation and high water vapor contents of storm events provide a significant amount. The attenuation and emission in this case complicates the observed upwelling brightness temperature (TB) measurements beyond a normal retrieval algorithm’s capability to explain. A robust and physically-based radiative transfer model (RTM) is necessary to estimate the contribution of the atmosphere under extreme weather events, and one must be constructed to begin retrieving optimal ocean wind vectors. TCs provide a comprehensive severe event that can facilitate the development of such a model.

Relevant Publications:

Mims, A., R. Kroodsma, C. Ruf and D. McKague, “Windsat Retrieval of Ocean Surface Wind Speeds in Tropical Cyclones,” Proc. 2010 International Geoscience and Remote Sensing Symposium, Honolulu, HI, USA, pp. 1831-1834, 25 July 2010.

Ruf, C. S., A. M. Mims and C. C. Hennon,“The dependence of the microwave emissivity of the ocean on hurricane force wind speed,” Proc. 28th Conf. on Hurricanes and Tropical Meteo., Orlando, FL, 28 Apr-2 May 2008.