基于K指数的阿勒泰地区夏季气象干旱特征

利用阿勒泰地区7个气象站1981-2010年6-8月降水量以及计算得到的蒸发量和K指数,用经验正交函数分解（EOF）和旋转经验正交函数分解（REOF）方法,分析了近30 a阿勒泰地区夏季干旱特征,用最大熵谱和谐波分析方法对阿勒泰3个分区K干旱指数的主要周期进行了分析。结果显示：用K干旱指数为指标,阿勒泰地区中西部干旱发生频率高于偏东地区;全地区可分为3个区域,Ⅰ西南谷地平原,Ⅱ东部丘陵地区,Ⅲ北部山区;各分区夏季干旱总体呈下降趋势。阿勒泰干旱的空间分布除受大尺度天气系统影响外,还受地理位置、地形地势等多种因子影响。各区干旱存在准10 a的长周期和3～5 a短周期振荡,且相对稳定,但其显著周期及其年代变化差异较大。

Summer Drought in Altay Based on Drought KIndex

In this paper,the characteristics of summer drought in recent 30 years were analyzed using the EOF and REOF methods based on the monthly precipitation and evaporation data and the calculated and drought K  index at 7 meteorological stations in Altay,Xinjiang during the period from June to August from 1981 to 2010,and the maximum entropy spectrum and the harmonic analysis were used to analyze the major cycles of the drought K  index in three regions of Altay.The results showed that,according to the drought WTBX]KWTBZ] index,the drought occurring frequency in the western and central regions was higher than that in the eastern region of Altay.The study area could be divided into 3 regions,i.e.the southwestern valley plain region (region Ⅰ),eastern hilly region (region Ⅱ) and northern mountainous region (region Ⅲ).Summer drought intensity in these three regions was holistically in a decrease trend.The spatial distribution of drought was affected by not only the large scale weather system including precipitation change,but also by many other factors,such as geographical location and terrain.There were the relatively stable 10 year and 3-5 year fluctuations of drought,but their main periodic and annual changes were significant.