基于综合气象干旱指数（CI）的干旱时空动态格局分析——以甘肃省黄土高原区为例

借助ArcGIS9．3和SPSS数据软件平台，根据甘肃省黄土高原区33个气象站1962-2010实测气象资料，利用综合气象干旱指数（CI）对甘肃省黄土高原区近50年的干旱特征进行了时空分析。首先计算了各站历年逐日的CI指数，统计近50年各站点出现的干旱过程、各时段的干旱事件，在此基础上分析了甘肃省黄土高原区历年各地区干旱发生的覆盖范围、频率和不同等级干旱发生的多年平均天数，揭示了甘肃省黄土高原区干旱发生的时空差异和动态格局。分析结果表明，（1）甘肃省黄土高原区有大范围干旱发生的年份，夏季和秋季较多分别有13、8a，冬季最少，只有3a。（2）从空间尺度来看，甘肃省黄土高原区中兰州一榆中一靖远一带和庆阳北部属于高值区，而岷县、渭源一带属于低值区；106°E以西“临洮．通渭．天水”一带和庆阳东南部是干旱变幅最大的地方。（3）从季节尺度来看，夏季干旱频率和持续日数最多，春季、秋季次之，冬季最少。

Temporal and spatial analysis of drought for recent 50 years in Loess Plateau of Gansu province based on meteorological drought composite index

Drought, one of the most severe hazards resulting in significant economic loses in agriculture and industry, is a natural phenomenon caused by the imbalance between import and demand for moisture. In the context of global climate change, the drought intensity, frequency, and its spatial patterns have been changing. In this paper, based on ArcGIS9.3 and SPSS software platform, the observed meteorological data of 33 meteorological stations from1962 to 2010 in Loess Plateau of Gansu province of China were collected and a composite index （CI） of meteorological drought was used to analyze the temporal and spatial characteristics of drought in the area. Firstly, the historical day-to-day CI was calculated, and on the basis of the statistics on drought events in each station and each stage in recent 50 years, coverage area of drought in each station, the occurrence frequency and scope were com- puted and analyzed to reveal the temporal and spatial occurrence pattern of the meteorological droughts in different parts of Loess Plateau of Gansu province. The results were showed as follows. （1） The large area drought in whole Loess Plateau of Gansu province occurred mostly in summer and autumn but least in winter during the period of 1962 to 2010. （2） In view from space scale, The highest zone in Loess Plateau of Gansu province is in Lanzhou-Jingyuan region and the northern part of Qingyang region, but the lower zone is Minxian-Weiyuan region. Meanwhile, in Lintao-Tongwei-Tianshui region and the south-eastern part of Qingyang re- gion, the change range is the largest. （3） In summer, The annual and seasonal occurrence frequencies of the meteorological drought and lasting days of different grades in Loess Plateau of Gansu province was most, in winter, it is least.