基于VCI的2003—2017年广东省干旱时空变化特征分析

An Analysis of the Spatial-Temporal Characteristics of Drought in Guangdong Based on Vegetation Condition Index from 2003 to 2017

为了研究近年来广东省干旱情况的时空变化特征,利用8天250 m分辨率的MODIS地表反射率数据,计算了2003—2017年广东省植被状态指数(Vegetation Condition Index,VCI),并以VCI为干旱指标,采用趋势分析、频率分析和MK检验等方法,对全省干旱的时空特征和趋势进行了分析.结果表明:广东省2003—2017年间的VCI整体呈现显著的上升趋势,80.3%以上区域的VCI变化趋势倾向率为正值,表示全省大部分地区旱情逐年减轻;全省大部分区域发生干旱的频率在0.2~0.6之间,以中旱为主(发生频率:0.2~0.4),重旱较少出现(发生频率:0~0.2);广东省总体干旱面积占比逐年降低,中旱和重旱面积占比也呈现下降的趋势;2017年与2003年相比,总体干旱面积占比减少了39.5%;总体上看,广东省近年来干旱严重程度在逐年减轻,干旱面积也逐年减少.

The temporal and spatial changes of drought in Guangdong Province in recent years were studied.The vegetation condition index(VCI)was calculated using MODIS surface reflectance data of 8 days and 250m resolution.The spatial and temporal characteristics and trend of drought in Guangdong were analyzed using trend analysis,frequency analysis and the Mann-Kenddall trend test.The results show that the average VCI of Guangdong has been rising significantly from 2003 to 2017,and the trend rate of VCI change in more than 80.3%of the whole area is positive,indicating that the drought in most regions of the province is alleviated in the study period.The frequency of drought in most regions of the province is between 0.2 and 0.6,the main drought is moderate drought(frequency:0.2-0.4),and the severe drought is rare(frequency:0-0.2).The proportion of drought-affected area in Guangdong has also been decreasing gradually,and the proportions of moderate and severe drought-affected areas show the same trend.Compared with 2003,the proportion of drought-affected area in 2017 decreased by 39.5%.In gene-ral,the severity of drought in Guangdong is decreasing year by year.