利用GRACE时变重力场数据监测长江流域干旱

Drought Detection over Yangtze River Basin from GRACE Time-Variable Gravity Data

利用2003-01~2014-12 CSR和JPL的RL06 Mascon解、RL06球谐系数(SH)解及level-3等6种GRACE时变重力场模型数据和GPM数据产品,分别计算长江流域的水储量和降雨变化,并利用广义三角帽方法分析GRACE数据的不确定性,同时计算水储量亏损指数(WSDI),以监测和分析长江流域干旱的时空特征,并与改进的帕默尔指数(scPDSI)进行对比。结果表明:目前在反演水储量变化方面,Mascon方法的不确定性小于球谐系数法,JPL_M、CSR_M、CSR_L3、JPL_L3、CSR_SH和JPL_SH的具体不确定性分别为3.51 mm、3.78 mm、5.45 mm、9.87 mm、9.12 mm及10.71 mm;降雨是影响长江流域水储量变化的重要因素,两者的相关系数达0.67,同时两者都具有明显的季节性变化;水储量亏损指数探测到2003-01~2014-12长江流域共历经6次干旱事件,最长时间的干旱始于2003-02,持续24个月;最严重的干旱发生于2006年春季和2011年夏季,强度分别为2.15和1.97;平均水储量亏损指数的空间分布表明,2006-07~2007-06几乎整个长江流域都处于干旱状态,而2011-03~11干旱主要集中于长江流域下游、中游和上游东南地区。

We estimated the terrestrial water storage(TWS)variation of Yangtze from CSR and JPL Mascon solutions,CSR and JPL spherical harmonic(SH)solutions and level-3 products and then calculated the uncertainties of these solutions by the generalized three-cornered hat method.Then evaluated the precipitation variation based on global precipitation measurement(GPM)product.This study also introduced water storage deficit index(WSDI)to analyse the spatial and temporal feature of drought events of Yangtze,compared with scPDSI(self-calibrated Palmer drought severity index).The results showed that:Mascon solution’s uncertainty is less than SH and the uncertainty of JPL_M,CSR_M,CSR_L3,JPL_L3,CSR_SH and JPL_SH is 3.51 mm,3.78 mm,5.45 mm,9.87 mm,9.12 mm,10.71 mm,respectively;Precipitation,which shows significant seasonal variation as well as TWS,with correlation coefficients 0.67,is the important trigger of TWS change in Yangtze;We detected six drought events in Yangtze based on WSDI from 2003-01 to 2014-12,with the longest duration of 24 month starting from 2003-02.2006 summer and 2011 spring experienced the severest droughts with intensity of 2.15 and 1.97,respectively.Spatial distribution of mean WSDI in Yangtze indicated that the drought,starting from 2006-07 to 2007-06,almost hit all the region of Yangtze basin while the drought that began in 2011-03 to 2011-11 appeared in downstream,midstream and northwest upstream of Yangtze basin.