基于卫星降水的鄱阳湖流域旱涝分析及其可靠性检验

ANALYSIS ON FLOOD/DROUGHT IN POYANG LAKE BASIN BASED ON SATELLITE PRECIPITATION AND ITS RELIABILITY VALIDATION

基于热带测雨卫星（TRMM）3842降水数据，通过z指数方法对鄱阳湖流域1998年1月～2010年12月旱涝的时空分布进行分析，并利用流域内15个雨量站观测降雨数据同样采用z指数方法分析流域旱涝变化，与TRMM结果进行对比，检验其精度和可靠性。结果显示：TRMM降水与地面雨量站观测降雨具有较高的一致性，能正确反映流域的降水情况；其计算的z指数在1998~2010年以0为中心呈锯齿状增大减小交替变化，所反映的洪涝事件主要发生在4～6月，占全年的60％左右，而干旱主要发生在9月～翌年1月份，其与鄱阳湖流域降水的年内分布特征是一致的；同时，基于TRMM降水反映的流域旱涝等级与降雨量的空间分布基本一致，TRMM降水能够用于流域旱涝的空间分布监测。

Flood/drought is one of the most influential climatic disasters in Poyang Lake basin. In traditional flood/drought monitoring, precipitation data used are usually from ground meteorological observation sites. However, due to the heterogeneity of regional precipitation over space and time, quantity and spatial distributions of meteorological stations frequently limit the overall accuracy of the regional flood/drought analysis. As one major means of space-based observations,in recent years, satellite remote sensing has become an increasingly important technique for region precipitation change monitoring. In this paper, TRMM （Tropical Rainfall Measuring Mission） satellite 3B42 precipitation data in Poyang Lake basin,firstly,were evaluated and compared through the bias of rainfall amount and occurrence frequency under different rainfall intensity, and then be used to reflect the spatio-temporal distribution characteristics of floods/droughts by the Z index method in Poyang Lake basin from January 1998 to December 2010. Their reliability was also validated by the 15 rain gauge stations in the basin using the same method. The results showed as follows. （1） The occurrence frequency and rainfall amount contributions of daily TRMM precipitation under different rainfall intensity had a high level of consistency with ground gauges observation. And at monthly scale, the high correlation coefficient between observed rainfall data and TRMM grid precipitation indicated that the TRMM precipitation could correctly reflect the rainfall in Poyang Lake basin. （2） Z index calculated by TRMM precipitation showed an increase-decrease alternant variation around 0 between 1998 and 2010. Their variation process and trends were consistent with the results of two rain gauges data and the correlation coefficients were 0. 896 and 0. 914,respectively. （3） The flood events in Poyang Lake basin occurred mainly from April to June and accounted for about 60% ,which was also the main wet season of Poyang I.ake basin, and the drought occurred mainly from September to January of the following year. And their distribution patterns were consistent with the annual distribution characteristics of precipitation. （4） The spatial distribution of Z index and flood/drought grades based on TRMM precipitation was consistent with the distribution of rainfall in April, 2010 and November, 2007, which represented the wet and dry month respectively. TRMM precipitation data can be used to evaluate the area and severity of flood or drought in Poyang Lake basin.