大同市气象干旱变化趋势分析

Analysis on Characteristics Change of Atmospheric Drought in Datong City

基于1955—2009年大同市年、月降水资料,利用降水距平百分率作为气象干旱指标,分析了大同气象干旱发生年、季特征时间演变及对农业的影响。研究表明,近55年来大同市年降水量以8.6mm/10年速度递减;共出现了20个旱年,出现频率为36%,平均每2.8年出现1个旱年;大同四季干旱发生频率依次为春季32.7%、冬季30.9%、秋季25.4%、夏季21.8%;冬季重旱年最多,其次是夏季,春季、秋季重旱年较少。秋季向湿润化发展趋势不明显;春、夏、冬季干旱均有增强趋势,造成了大同干旱化增强的总趋势。以农作物关键期(4—9月)降水量分析,从1980年开始大同由总体偏涝转为偏旱。年、季干旱出现频率同样表明,20世纪80年代干旱出现频率明显增强,到90年代达到极值。结合农业旱灾资料,进一步分析气象干旱对农业的影响,并提出了抗旱对策和建议,旨在对当地防旱减灾起到积极的指导作用。

Based on the yearly and monthly precipitation data（1955-2009）of Datong,using a meteorological drought index as atmospheric percentage,the author analyzed the meteorological drought occurring year in Datong,time evolution and the impact on agriculture.The results showed the annual precipitation decreased by 8.6 mm/10 a in 55 years,meanwhile,there were 20 dry years in total,and the drought frequency was 36%,which meant that there was a drought year every 2.8 years.The frequency of dry season were 32.7% in spring,30.9% in winter,25.4% in autumn and 21.8% in summer.Severe winter drought years was the most,followed by summer,but severe spring and autumn drought years were less.The humid autumn trend was not apparent;spring,summer and winter drought which were increasing,resulting in enhanced drought general trend in Datong.The author analyzed the precipitation in the key period of crops（April to September）,since 1980 the overall bias by the floods to partial drought in Datong.The frequency of the annual and quarterly drought pointed to the evident raise of the drought frequency during 1980s.And it reached its extreme value in 1990s.Combining the agricultural drought data,the author further analyzed the influence of meteorological drought on agriculture,and put forward some countermeasures and suggestions,expecting to have positive guidance for the local drought control.