基于MCI指标的甘肃省近50年干旱特征分析

摘要

Based on the data of MCI value during 1961—2010 from the national climate center,we worked for the drought characteristics in Gansu province .The study shows that:the drought occurred in higher frequency in spring (55 .4%)and summer (55 .0%),and relatively lower frequency in autumn (41 .1%)and winter(46 .3%).The large-scale drought in the whole area occurred mostly in summer and autumn,but least in winter .Moreover,the drought-suf-fered area is still extended in various seasons during the latest 50 years .Considering frequency and severity of drought, longer different grades of drought occur in spring,and easily develop to the severe drought .In summer and winter,light and mederate drought easily happens in large area,but rarely severe drought occurs .Drought in autumn is mild with short duration Compared regional difference of drought occurrence,Gannan area has less drought,while eastern part of Hexi,northern part of Longzhong and southern part of Longnan have higher drought frequency .In the latest 50years,an-nual average and daily mean of drought duration,drought-suffered stations proportion and drought intensity were fluctuant without a significant sense .Drought intensity is the strongest in spring and the weakest in autumn .The significant nega-tive correlation was observed between drought intensity and rainless days .%基于甘肃省16个气象站1961—2010年改进气象干旱指标（MCI）对甘肃省近50年不同季节的干旱特征进行了统计分析。结果表明：春旱和夏旱发生频率最高，为55．4％和55．0％；秋旱发生频率最低，为41．1％；冬季干旱发生频率为46．3％。全省夏秋季易出现大范围干旱，冬季较少。近50年来，干旱发生范围在全年各季节都有不同程度增加。春季各等级干旱发生天数均较高，且更容易发展成为重旱甚至特旱；夏季和冬季易发生大范围的轻旱和中旱，而严重干旱发生较少；秋季干旱发生日数最少，且干旱强度也最轻。总的来说，甘南地区干旱发生最少，而河西东部、陇中北部和陇南南部发生干旱较多。近50年，研究区干旱平均持续日数、发生干旱站次比以及干旱强度虽有不同程度增加或减少趋势，但变化并不显著。春季干旱强度最强，秋季最弱。干旱强度与无雨日数有显著负相关关系。