7种干旱评估指标在广东北江流域应用中的对比分析

本文基于Pa、MI、SPI、ZI、SPEI干旱评估指标,对广东北江流域干旱等级进行评估,统计出各指标干旱等级不一致的情况,然后通过各指标间的等级不一致率及等级差值来分析各指标之间的异同,同时根据CI、AWTP指标的定义,统计出季节尺度的干旱持续时间CI-N(多年均值为CI-L)及与之对应的一次等价连续干旱期AWTP-N(多年均值为AWTP-L)并进行对比分析.在Pa、MI、SPI、ZI、SPEI指标的对比中发现,Pa与MI评估的干旱等级较接近,ZI、SPI、SPEI评估的干旱等级较相似,但Pa、MI与ZI、SPI、SPEI评估的干旱等级存在较大差别.这些差别主要原因是各指标计算方法不同造成的.各指标间干旱等级不一致率较高的主要集中在秋季(10月、11月)和冬季(12月、1月).对比分析发现MI比较Pa评估的干旱等级更为合理；SPEI比较ZI、SPI评估的干旱等级更为合理；在对气温变化造成蒸发从而影响干旱等级变化的反应方面,SPEI优于MI；结合历史实际干旱资料对比分析发现SPEI对干旱的评估更接近实际情况.在CI与AWTP对比中发现,二者评估的干旱结果存在较大差别甚至没有必然的联系.这些分析结果也可为干旱评估指标的改进或新指标的建立提供依据.

Comparative Analysis of Seven Drought Evaluation Indices in the Beijiang River Basin, Guangdong

Much work has looked at variation in drought based on different index and regional scales, but comparisons that apply several drought indices in the same region are lacking. We used daily precipitation and mean temperature for Nanxiong, Lianzhou, Shaoguan, Fogang and Guangning stations in the Beijiang River basin of Guangdong from at least 1957 until 2011. The Pa, MI, SPI, ZI and SPEI drought evaluation indexes were used. The drought duration seasonal scale CI-N (multiple-years mean: CI-L) and corresponding continuous period of drought AWTP-N (multiple-years mean: AWTP-L) were identified according to definition of CI and AWTP. The drought degree evaluated by Pa was closer to MI. SPI was more similar to ZI and SPEI, but there were larger differences between Pa, MI and other indices. Comparative analysis showed a higher inconsistent rate of drought grade in Autumn (October, November) and Winter (January, December), but the inconsistent rate is low in other months and the results from different evaluation indices have little difference. The drought degree evaluated by MI was more reasonable than Pa; SPEI is more reasonable than ZI and SPI. In the aspect of response to temperature changes, for evaluation of drought grade, SPEI was prior to MI. Compared to historical drought materials, the drought degree evaluated by SPEI was closer to the real situation than MI. Comparative analyses can provide a foundation for improving evaluation indices or establishing new indices to better evaluate drought.