TRMM and Rain gauge dataset for Adama,Ethiopia.

Drought – a very critical natural process which greatly affects the agriculture which is the major source for human existence. Various researches, experiments have been done in the past which monitored meteorological droughts using standardized indices of precipitation deficits. They mostly relied on rain gauge-based measurements which has the limitations of spatial coverage, data availability and cost efficiency. The purpose of this paper is the potential to apply the satellite derived rainfall product to monitor meteorological drought. Most common is the Standard Precipitation Index (SPI) for research and operational applications on meteorological and agricultural drought monitoring and early warning. The monthly precipitation data accuracy of TRMM (the Tropical Rainfall Measurement Mission) 3B43, was implemented by comparison with the rainfall data of five ground stations in and around Adama woreda from 1998 to 2015. The substantial correlations between the two sources were found during August, and the decision coefficients (R2) are 0.10, 0.25, 0.065, 0.05 and 0.49 respectively. TRMM rainfall data from 1998 to 2015 were used to calculate 3,6,9 and 12-month Standard Precipitation Index (SPI) pixel by pixel for Adama woreda. This 3,6,9 and 12 month SPI was incorporated to depict spatial patterns of meteorological drought and its severity during typical drought and wet years. Further, time series of SPI were considered to assess the drought risk in Adama woreda. We clinch that the TRMM product can properly monitor meteorological droughts though it has relatively short dataset length (~15 years). Lastly, we suggest an assimilation of rain gauge and satellite-based precipitation data to provide more robust estimates of meteorological drought severity.干旱是一种极为关键的自然过程，对作为人类生存核心依托的农业产生极大影响。过往已有多项研究与实验采用降水亏缺标准化指数开展气象干旱监测，此类研究多依赖基于雨量计的观测手段，但该手段存在空间覆盖范围有限、数据可获取性不足以及成本效益欠佳等局限。本文旨在探究采用卫星反演降水产品开展气象干旱监测的可行性，其中标准化降水指数（Standard Precipitation Index, SPI）是气象与农业干旱监测及预警领域研究与业务应用中最常用的指数。本文以1998至2015年期间阿达马沃雷达（Adama woreda）及其周边5个地面站点的降水数据为参照，对热带降雨测量任务（Tropical Rainfall Measurement Mission, TRMM）3B43产品的月降水数据精度进行了验证。研究发现，两类数据源在8月存在显著相关性，其决定系数（R²）依次为0.10、0.25、0.065、0.05与0.49。本文利用1998至2015年的TRMM降水数据，针对阿达马沃雷达逐像元计算了3、6、9及12个月尺度的标准化降水指数（SPI），利用该多尺度SPI可刻画典型干旱年与湿润年的气象干旱空间分布格局及其严重程度。此外，通过SPI时间序列可评估阿达马沃雷达的干旱风险。最终研究结论表明：尽管TRMM产品的数据集时长较短（约15年），但其可有效开展气象干旱监测。最后，本文建议融合雨量计与卫星反演降水数据，以获得更为可靠的气象干旱严重程度估算结果。