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| Characteristics analysis of short time strong precipitation process in a weak echo tropical depression |
| Su Limin1, Ma Zhongyuan2 , Nie Xiongping1, Chen Yi1, Wang Xiaoqian1 |
1.Yichun Meteorological Bureau of Jiangxi, Yichun 336000;
2.Jiangxi Meteorological Science Institute, Nanchang 330046 |
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Abstract By using routine synoptic data, meteorological elements from AWS, 3D cloud pictures, data of radar echoes from a single station, Web GIS radar mosaic products and wind profiler products, based on the methods of statistics, contrast analysis and feature extraction, the short time strong precipitation process in No.7 strongest Typhoon Soulik (tropical depression) in 2013 over Yichun city of Jiangxi province was analyzed.The results show that during the short time strong precipitation process of Typhoon Soulik(tropical depression), Yichun is controlled by the low-pressure center in the east and influenced by a wide range of spiral cloud at the south of typhoon eye.The strong precipitation center is found move from northwest to southeast when the spiral rain band counter-clockwise move from north to south.The 0714 Typhoon Soulik process shows weak echo with closely structure and banded and flocculent integration.The echo intensity is only 35-45 dBz.Before and after short time strong precipitation, meteorological elements of single station appear steady temperature and saturated humidity.The air pressure is lower and rises gently after strong precipitation occurred with small 2min average wind speed.There is wind direction shear during strong precipitation.This process have typical characteristic of the rainstorm that a longer rainfall duration and with ultra-short time strong precipitation.The characteristics of wind profiler products are more obvious during short time strong precipitation of Typhoon Soulik(tropical depression).On the horizontal wind direction and speed of wind profiler, it can be seen that upper air prevails northwest wind and lower altitude presents southwest wind.The overall wind speed is average within the range of 12-20 m/s, and the lowest height dip is at 600 m AGL.There is a vertical shear of wind direction and speed in upper and lower air, but the shear strength is obvious smaller than other severe convection weather.The radial velocity is positive and its largest value is 8 m/s that emerges at the strongest rainfall intensity.Velocity spectrum width displays large value or small ones alternately between upper and lower altitude.The SNR is up to 60-70 dB.The vertical wind velocity is up to 8 m/s that is influenced by raindrops terminal velocity.The structure constant C2n of atmospheric refractivity presents maximum value from -15 m-2/3 to -14 m-2/3, which is mainly caused by larger and dense raindrops in typhoon precipitation.
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Received: 29 January 2014
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2014, Vol. 31 
