Droughts in a warming climate: A global assessment of Standardized precipitation index (SPI) and Reconnaissance drought index (RDI)
Droughts in a warming climate: A global assessment of Standardized precipitation index (SPI) and Reconnaissance drought index (RDI)
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DOI：
10.1016/j.jhydrol.2014.09.071
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发表时间：
2015-07
影响因子：
6.4
通讯作者：
M. A. Zarch;B. Sivakumar;Ashish Sharma
中科院分区：
文献类型：
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作者：
M. A. Zarch;B. Sivakumar;Ashish Sharma
干旱和干旱都表明水分供应不平衡。干旱是一种暂时的自然灾害，而干旱是一种持续的气候特征。本文研究了考虑潜在蒸散发（PET）和不考虑潜在蒸散发（PET）的不同干旱区干旱特征的变化，以更好地评估气候变暖下的干旱。采用两种干旱指数：(1)标准化降水指数（SPI），该指数完全基于降水；(2)侦察干旱指数（RDI），该指数除考虑降水量外，还考虑了PET。首先将这两个指数应用于东安格利亚大学气候研究中心（CRU） TS 3.1数据库1960-2009年的降水和PET观测资料。结果表明，尽管所有干旱区都经历了下降和上升的干旱趋势，但大部分干旱区没有明显的趋势。然而，SPI和RDI的一致性从极端干旱区向湿润区递减。在半干旱区、半湿润区和湿润区，各指数表现出不同的变化趋势，RDI呈现出更多的减少趋势（即变干）。1998年以前的SPI通常比RDI显示出更多的干旱易发地区，而1998年以后的SPI则相反。考虑到观测记录中已知的PET变化，以及随着全球变暖加剧而预期的增加，这些结果表明，随着全球变暖加剧，RDI将始终不同于SPI。利用耦合模式比对项目（CMIP5）和RCP8.5（代表性浓度路径）的第五阶段，CSIRO（澳大利亚联邦科学与工业研究组织）Mk3.6全球气候模式（GCM）的历史和未来气候预测进一步验证了这一假设。在这种情况下，PET是使用FAO56-PM模型来评估RDI的。结果表明，SPI和RDI之间的一致性受到影响，并随着时间（1850年至2100年）显著降低。因此，面对气候变化，PET作为水文循环的重要组成部分，在干旱模拟中不可忽视。
Both drought and aridity indicate imbalance in water availability. While drought is a natural temporal hazard, aridity is a constant climatic feature. This paper investigates the changes in drought characteristics across different aridity zones with and without consideration of potential evapotranspiration (PET), as a means to better assess drought in a warming climate. Two drought indexes are employed: (1) Standardized precipitation index (SPI), which is solely based on precipitation; and (2) Reconnaissance drought index (RDI), which, in addition to precipitation, takes PET into account. The two indexes are first employed to observed precipitation and PET data for the period 1960–2009 from the CRU (Climate Research Unit, University of East Anglia) TS 3.1 database. The results indicate that although all the aridity zones experience both downward and upward drought trends, no significant trend is found over large parts of the zones. However, the agreement between SPI and RDI reduces from the hyper-arid zone on one extreme toward the humid zone on the other. In the three more humid zones (i.e. semi-arid, sub-humid, and humid), the indexes exhibit different trends, with RDI showing more decreasing trends (i.e. becoming drier). While SPI generally shows more drought prone areas than RDI for the pre-1998 period, the opposite is observed for the post-1998 period. Given the known changes to PET in observed records, and also expected increases as global warming intensifies, these results suggest that RDI will be consistently different to the SPI as global warming intensifies. This hypothesis is further tested for historic and future climate projections from the CSIRO (Commonwealth Scientific and Industrial Research Organisation, Australia) Mk3.6 global climate model (GCM), with use of the fifth phase of the Coupled Model Intercomparison Project (CMIP5) and RCP8.5 (Representative Concentration Pathways). In this case, PET is calculated using FAO56-PM model for assessment of RDI. The results suggest that agreement between SPI and RDI is affected and decreases remarkably over time (between 1850 and 2100). All these lead to the conclusion that, in the face of climate change, PET, an important component in the hydrologic cycle, should not be ignored in drought modeling.