| Chinese meteorological Satellite FY-3A launched at 2008, it is mounted with advanced microwave detector, so it has a strong atmospheric vertical detection capability. National Satellite Meteorological Center (NSMC) released FY-3A air humidity product, it has widely coverage, highly spatial resolution and broadly prospect of application. What the product characteristics look like, how to exert its advantages, it is a problem urgently need to solve. The characteristics of FY-3 A air humidity product, the application technology, and the diagnosis effect during Meiyu Heavy Precipitation at Jianghuai Valley are discussed in this paper.The results are as follows:The FY-3A air humidity product is air-moisture ratio, the element can describe the moisture conditions with fine size at atmospheric levels covering continent and sea. Before formally using the moisture element, it needs to be preprocessed. It is included several steps that are to interpolate the standard pressure levels from the satellite pressure levels, to delete those data which are relatively few outliers by theBiweight Check, to smooth the "noise" caused by satellite monitoring way by smoothing method, to transport the monitoring moisture element from the satellite coordinate into the traditional Latitude -Longitude coordinate, etc. It is conformed that the fine features of satellite monitoring element are kept satisfactory after preprocessing by co-correlation test and obtain the standard data base.Satellite air-moisture ratio fields wet area is well correspond with rainfall area. Also rainfall areas correspond with high-energy, strong potential instability, and high water vapor flux area. The results show that FY-3A air humidity product cans accurate show the rainfall area and dynamic Characteristics of heavy rain systems. The value of FY-3A air humidity product is lower than the sounding data values, in the range of 2g/kg.To apply the FY-3A air humidity product on moisture-dynamic diagnosis of Meiyu heavy precipitation at Jianghuai valley, the main precipitation systems in Meiyu season are shallow low vortex and convergence line. According to the statistics for near 5 years, there are 3/5 low vortices existing in southern Jianghuai valley and about 2/3 convergence lines living in northern Jianghuai valley. At synthesized moisture fields, the convergence lines are with remarkable air-moisture ratio front region along latitudeward, the low vortices are with the moisture tongue along longitueward and the moisture isopleths show a cyclonic mixture of dry-moisture air masses in low vortices. Compare with the FNL reanalysis moisture ratio fields the satellite air-moisture ratio fields wet area is more clear and accurate in heavy rain systems.Using both FY-3A satellite air-moisture ratio fields and FNL reanalysis streamline fields at air low levels, the systematical rainfall area can be estimated, and the air precipitable water at atmospheric low levels (1000-850hPa) calculated by satellite air-moisture ratio is proportional to rainfall intensity, and the pseudo-equivalent potential temperature calculated from satellite air-moisture ratio can show high energy area and high energy front companied with rainfall area. To apply the moisture-dynamic diagnostic methods on nearshore area precipitation estimation, the precipitation area and intensity is close to the practical situation, it will be a good compensation for sea precipitation. |
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