西北地区气象干旱监测指数的研究和应用

Research and Application of Meteorological Drought Monitoring Indexes in Northwest China

为了更有效地监测西北地区干旱,综合西北地区广泛应用的Z指数方法和帕默尔气象干旱指数基本原理的优点,选取西北地区138个代表站1961—2000年40年逐月降水量资料,分东、西两片分别建立了西北地区东部和西部的单站气象干旱监测指数。在此基础上建立了区域干旱指数,确定了区域旱涝等级的划分标准。以计算得到的干旱指数与历史旱情记录进行了对比验证,并对计算结果做了进一步的统计分析。结果表明:干旱指数对西北地区旱情的反映符合历史实际;西北地区东部近几十年来干旱发生的次数和强度较西部更重;从长期演变趋势看,西北地区东部干旱发生频率呈现出上升的趋势,尤其是1990年代中期后上升趋势更为明显,而西北地区西部则呈现下降趋势;西北地区东部3、4、5、6月份的区域干旱均具有5～10年的周期,而西北地区西部区域干旱的周期性不明显。这些指数的建立,将为更好地开展西北地区的干旱监测、诊断业务提供气象意义明显且应用简便的气象干旱指数。

To monitor drought in Northwest China more effectively, the drought monitoring index for east and west part of NW China was established respectively based on the principles of Z index and Palmer index. The monthly precipitation data in 138 representative stations of NW China（1961-2000） were used as basic data. A regional drought monitoring index was further developed, and the grades for regional drought were also determined. Comparing the computed drought index with some recorded drought situation, it is found that these indexes can reflect the severity of meteorological drought in NW China. Furthermore, the drought characteristics were analyzed by using some statistical methods. The result shows that the drought in the east part was more severe than in the west in recent decades. In a long term, the drought frequency shows an increasing trend in the east part while a decreasing trend in the west. The meteorological drought in the east part from March to June has a period of 5 to 10 years, while the periodicity isn＇ t evident in the west. These indexes have an obvious meteorology meaning and can be applied simply in the drought monitoring practices of NW China.