基于CI指数的甘肃省黄土高原地区气象干旱的变化趋势分析

Trend Analysis of the Variation of Meteorological Drought in Loess Plateau of Gansu Province Based on Comprehensive Meteorological Drought Index

基于甘肃省黄土高原区33个气象站1962-2010年气象资料,利用综合气象干旱指数(CI)对其近50a的干旱频率和平均持续时间的空间分布、干旱强度趋势变化和极端干旱事件频次进行了分析,此基础上应用基于分型理论的R/S方法对干旱强度未来变化趋势进行了预测.结果表明:甘肃省黄土高原区干旱发生频率和多年平均持续天数在兰州-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.20世纪90年代以来,干旱强度增大的较快,四季均呈现出干旱强度变大的趋势,其中春、秋季干旱强度加剧的趋势明显,夏季近10a都处于非常严重的干旱状态,但未通过0.01的显著性检验;20世纪60年代至今,极端干旱事件发生频次快速增多.四季干旱强度Hurst指数H均大于0.5,同时分维数D均小于1.5,因此,未来一段时间干旱强度仍然保持与过去相一致的变化趋势.研究结果可为相关部门制定相应抗旱对策提供科学依据.

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 this paper,based on ArcGIS 9.3 and Fortran6.5 software platform,the observed meteorological data of 33 meteorological stations from 1962 to 2010 in Loess Plateau of Gansu Province of China were collected and a comprehensive meteorological drought index was used to analyze the spatial distributions of drought frequency and duration,the trends of drought intensity and frequency in the area.Based on the above analysis,the future trends of drought intensity are forecast by using the method of rescaled range analysis.The results show： 1） the highest drought intensity in the Loess Plateau of Gansu Province is located in Lanzhou-Jingyuan area and the northern part of Qingyang Municipality,with a large change range in Lintao and Tongwei Counties,Tianshui Municipality and the southeastern part of Qingyang Municipality.2） Drought intensity has significantly increased since the 1990s.The increase covers the four seasons,but in spring and autumn it is more obvious.In the last 10 years,summer drought has been most serious,but has not passed the significance test of 0.01 yet.3） Since the 1960s,the frequency of extreme drought has increased significantly.4） The Hurst indices of the drought intensity are all larger than 0.5 for all seasons.The fractal dimensions,meanwhile,are all less than 1.5.These indicate that drought intensity would keep the trend same as that in the past.This study provides a basis for developing appropriate measures to reduce the loss due to droughts in Loess Plateau of Gansu Province.