26th Conference on Hurricanes and Tropical Meteorology


A Method of Applying Quikscat Data for Tropical Cyclone Initialization

Chi-Sann Liou, NRL, Monterey, CA; and Y. Jin

Lack of enough observations to properly initialize tropical cyclones (TCs) is still a major obstacle in TC forecast by dynamic models. Quikscat data are surface wind velocity observations measured by the backscattering of active satellite-borne radar signals over ocean. The satellite measurement has a relatively wide scanning swath (1800km) and no contamination by clouds that make it very valuable in observing tropical cyclone circulation. However, there are limitations to the Quikscat data as well. For example, the polar orbiting satellite measurement is only available over ocean with an irregular observing time about twice a day. The measurement is very accurate in wind speed but there are 4 possible wind direction solutions that require further retrieval to select one. The measurement is contaminated by heavy rain that reduces its accuracy in measuring surface winds near cyclone centers. Furthermore, the surface wind observations have a relatively small impact on 3-dimensional TC circulation analysis if they are analyzed as single level data by a 3-dimensinal data analysis method. To work around with these limitations, we have developed a method at NRL to apply Quikscat data for TC initialization in the Navy operational mesoscale model, Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPSTM). The method objectively determines the 34 kt and 50 kt wind radii of observed TCs from operationally retrieved Quikscat data and then use these TC structure parameters in the TC initialization for COAMPS. This paper will discuss the objective method as well as the results of numerical experiments conducted to test its impact on TC track and structure forecast by COAMPS.

extended abstract  Extended Abstract (104K)

Poster Session 1, Posters
Wednesday, 5 May 2004, 1:30 PM-1:30 PM, Richelieu Room

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