考虑多尺度和蒸散影响的新干旱指数研究——以云南为例

A New Drought Index Study that Takes into Account a Multi-timescale and the Effects of Evapotranspiration——Taking Yunnan as an Example

构建适宜的干旱指标是精准实时监测干旱发生发展的基础,本研究从多尺度对土壤湿度和农作物受旱面积的响应出发,构建了一个新气象干旱指数DI,其更适用于干旱的实时监测。DI是基于考虑实时蒸散影响的短时间尺度相对湿润度指数(MI30)、中时间尺度标准化权重降水指数(SPIW60)及考虑蒸散气候异常影响的长时间尺度标准化降水蒸散指数(SPEI120)三种单时间尺度干旱指数的综合。研究以中国云南省为试验对象,利用125个国家气象站逐日降水量和平均气温资料以及历史干旱灾情数据,运用EID理论方法研制了干旱综合强度指标,统计了常用干旱指数的干旱综合强度,开展了各干旱指数对典型干旱过程监测对比检验,以及与实际干旱受灾面积的相关分析。结果表明:长时间尺度的干旱指数强度对干旱灾情的响应优于短时间尺度,在实时监测干旱时也更稳定,不易出现不合理的跳跃现象;而短时间尺度的干旱指数对降水的响应较长时间尺度的指数更为敏感,能及时监测强降水引起的干旱缓解作用。包含多种时间尺度的综合干旱指数(DI、MCI)比单一时间尺度的干旱指数在监测识别干旱和反映干旱灾害影响方面,具有两者兼顾的优势。本研究新构建的综合干旱指数DI在单项指数组成上和各分项权重系数确定上较MCI更简单,DI与干旱灾情的相关系数达0.63,优于MCI,实时监测的敏感性和稳定性方面相当,更适用于云南地区干旱监测和干旱评估业务。本研究可为实时干旱监测选取适宜的指标提供参考和指导。

Based on the response of a multiscale drought index to soil moisture and the drought-affected crop area,this study constructed a new composite-index DI that consists of a short time scale(the last 30 days)relative to the Humidity Index(MI30)considering evapotranspiration,a medium-length time scale(the last 60 days)Standardized Precipitation Index with Weighted coefficients(SPIW60),and a long time scale(the last 120 days)Standardized Precipitation Evapotranspiration Index considering evapotranspiration(SPEI120).DI is more suitable for real-time drought monitoring.Based on the daily precipitation and average temperature data of 125 national meteorological stations in Yunnan Province,China,comprehensive drought intensities were calculated using various drought indexes.The comprehensive drought intensity was developed based on EID theory.In addition,the typical drought processes of each drought index were compared,and a correlation analysis was performed with the drought-affected crop areas.The results show that the response of the drought index intensity with a long time scale to drought disaster conditions is better than that of the index with a short time scale,further,the index incorporating a long time scale is more stable in real-time drought monitoring and does not easily output unreasonable jumps;while the response of the drought index intensity with a short time scale to precipitation is more sensitive and can monitor drought mitigation caused by effective precipitation in a timely manner.Composite drought indexes(DI,MCI)with multiple time scales have the advantages of both monitoring and identifying drought and reflecting the impacts of drought disasters.The newly constructed composite drought index,DI,is simpler than MCI in the index composition and the determination of coefficient weights.The correlation coefficient between DI and the drought-affected crop area is 0.63,which is better than that of MCI.The sensitivity and stability of real-time drought monitoring are equivalent between DI and MCI.DI is more suitable than MCI for drought monitoring and drought assessments in Yunnan Province.This study can provide useful guidance for selecting suitable indicators for real-time drought monitoring.