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摘要
A tropical cyclone (TC) circulation Tracking Radar Echo by Correlation technique (T-TREC) developed recently is applied to derive horizontal winds from single Doppler radar reflectivity Z data (combined with radial velocity V-r data when available). The typically much longer maximum range of Z observations compared to V-r data allows for much larger spatial coverage of the T-TREC-retrieved winds (V-TREC) when a TC first enters the maximum range of a coastal radar. Retrieved using data from more than one scan volume, the T-TREC winds also contain valuable cross-beam wind information. The V-TREC or V-r data at 30-min intervals are assimilated into the Advanced Regional Prediction System (ARPS) model at 3-km grid spacing using an ensemble Kalman filter, over a 2-h window shortly after Typhoon Jangmi (2008) entered the V-r coverage area of an operational weather radar of Taiwan. The assimilation of V-TREC data produces analyses of the typhoon structure and intensity that more closely match observations than analyses produced using V-r data or the reference Global Forecast System (GFS) analysis. Subsequent 28-h forecasts of intensity, track, structure, and precipitation are also improved by assimilating V-TREC data. Further sensitivity experiments show that assimilation of V-TREC data can build up a reasonably strong vortex in 1 h, while a longer assimilation period is required to spin up the vortex when assimilating V-r. Although the difference between assimilating V-TREC and V-r is smaller when the assimilation window is longer, the improvement from assimilating V-TREC is still evident. Assimilating Z data in addition to V-r or V-TREC results in little further improvement.
- 出版日期2014-5
- 单位南京大学
