【作者】 熊光洁；

【导师】 李崇银； 王式功；

【作者基本信息】 兰州大学 ， 气象学， 2013， 硕士

【摘要】 针对近几年我国西南地区频繁出现干旱的现实问题。本文首先介绍了一个新的干旱指数—标准化降水蒸散指数(Standardized Precipitation Evapotranspiration Index, SPEI)。然后,利用全国160个气象站1951年1月-2012年12月的月降水量和平均气温资料,参考过去该地区发生的干旱灾害历史资料,研究了SPEI指数与另外两个常用的干旱指数对西南地区不同时间尺度干旱的表征能力。其次,利用1961年-2012年中国西南地区86个气象站逐月降水量和平均气温资料,以SPEI作为旱涝等级划分标准,研究了近50年我国西南地区不同时间尺度的干旱变化特征。最后,为进一步研究冬季干旱的成因,合成分析了导致西南地区冬季干旱的大气环流、南支槽、海温等方面的异常特征。分析结果表明：(1) SPEI能抓住降水和蒸发这两个影响干早的重要决定因素,对西南地区季、半年、年尺度的干旱有较好的表征能力；SPI在分析西南地区不同时间尺度干旱时：对于年尺度的干旱表征是适用的；对半年尺度的干旱,SPI是适用的,但表征能力不及SPEI;对于季节尺度的干旱,春、秋两季是适用的；M指数在分析西南地区不同时间尺度干旱时：对于年尺度的干早,部分站点是适用的；对半年尺度的干旱,夏半年是适用的,对于季节尺度的干旱,春、夏两季是适用的。(2)通过统计分析中国西南地区已发生的干旱历史资料,发现该地区较易发生半年尺度和季节尺度的干旱,其中季节尺度干旱次数占总干旱次数的比例为62.3%；6个月尺度干旱频率在少雨期(11月—翌年4月)全区显著增加,而在多雨期(5月—10月)大部分区域呈缓慢减少趋势,减少最明显的区域在四川南部；3个月尺度干旱频率在春季变化不明显,秋季和冬季干旱频率显著增加,其中自2000年至今的十几年来增加趋势尤为显著,干旱化趋势严重。(3)研究发现赤道西太平洋海温偏高,东亚大槽偏弱,乌拉尔山与贝加尔湖之间的高压脊偏弱,同时青藏高原上空的下沉运动和东侧偏北气流异常以及南支槽附件出现反气旋环流异常对西南地区冬季干旱有重要影响。另外,当NAO(AO)持续处于负相位对西南地区干旱的发生有促进作用。更多还原

【Abstract】 Based on the problem that drought happened frequently in southwest China in recent years. This paper first introduces a new drought index—Standardized Precipitation Evapotranspiration Index(SPEI). Then, Referencing to historical data of past drought disasters of Southwest China, the applicability of the Relative Moisture Index, SPI and SPEI were studied base on the monthly precipitation and temperature data from Jan,1951to Dec,2012at18stations in Southwest China. Secondly, the characteristics of drought variations of the different time scales from1961to2012in southwest China also were studied, by using SPEI as droughts level division standard which is calculated based on monthly precipitation and average air temperature data from86meteorological stations. Finally, to further study the causes of winter drought, synthetic analysis lead to winter drought abnormal characteristics of the atmospheric circulation, southern trough and the SST in the Southwest.The analysis results show that:(1) The SPEI not only can grasp precipitation and evapotranspiration which are two important determinant effects of drought, but also is well applicable to characterizing drought events at time scales of3,6, and12months in Southwest China in the past62years. The SPI is applicable to characterizing drought events at time scales of6and12months, but it is inferior in description to the SPEI at time scales of6months; and it is applicable to characterizing drought events at time scales of3months both in spring and autumn. The Relative Moisture Index is applicable to characterizing drought events at time scales of12months in some meteorological stations; it is applicable in the summer half year to characterizing drought events at time scales of6months; it is applicable to characterize drought events at time scales of3months in both spring and summer. (2) Based on the statistic analysis of historical drought records of Southwest China, it is found that the drought frequency at6-months and3-months scale in this region happens more frequently, and the number of drought frequency at3-months scale accounts for62.3%of the total. The drought frequency at6-months scale shows a significant increasing trend in the drier period (November—April in the following year) in the whole research areas, and a slowly decreasing trend in the rainy period (May—October) in the most regions but particularly obvious in southern Sichuan area. The drought frequency at3-months scale does not indicate a significant trend in spring, however, it shows a significant increasing trend in autumn and winter. Especially since the year of2000, the drought trend has been the most serious.(3)This study found that the SST of equatorial western Pacific Ocean is high; the East Asia major trough and the high-pressure ridge between the Ural Mountains and Lake Baikal are both weak; and the downward motion above the Qinghai-tibet plateau, the anomalies of airflow in Northeast and the anomalies of the anticyclonic circulation near the southern trough have a impact on the drought in the Southwest in winter. Meanwhile, NAO(AO) remaining in negative phase promotes the drought in the Southwest.更多还原