近50年华北区域性气象干旱事件的特征分析

Study on Characteristics of Regional Drought Events over North China During the Past 50 Years

本文利用区域性极端事件客观识别法(OITREE),进行了1961—2010年华北地区区域性气象干旱事件的识别,确定了该方法中相应的参数组并识别得到100次事件,并对排名前15位的事件与文献记载情况逐一进行对比检验。结果表明OITREE方法对华北地区区域性气象干旱具有良好的识别能力。100次华北地区区域性气象干旱事件分为10次极端事件、20次重度事件、40次中等事件和30次轻度事件,其中1998年9月至1999年5月秋冬春连旱是华北地区强度最强的干旱事件。事件的持续时间一般在17~120 d、最大影响面积集中在(70~105)×10~4km^2之间,干旱事件具有较明显的季节特征,3—7和10—11月是事件的两个高发时段;华北南部为干旱多发区,其中河北、河南和山东三省交界为强度中心区域。重度(含)及以上的干旱事件可分为全境型、东部型、南部型、西部型、中部型和零散型6种分布类型,其中全境型出现机率最高。近50年华北地区区域性干旱事件频次、累积综合强度总体呈上升趋势,其主要原因可能是降水量减少所致,同时气温显著升高也起到了明显的推动作用。

The objective identification technique for regional extreme events(OITREE) is applied to detect the North China regional meteorological drought events during 1961-2010.The parameter values of the OITREE method are determined,and the results show that the OITREE method has a good capability in identifying the regional droughts in North China.In the study,100 events are identified,including 10 extreme events,20 severe events,40 moderate events and 30 slight events,in which the September 1998-May 1999 extreme drought in North China is the most serious meteorological drought event for the past 50 years.Further analysis reveals that the durations are generally between 17-120 d and the maximum impacted areas vary from 70×10~4 km^2 to 105×10~4 km^2.Meanwhile,the drought events have obvious seasonal features with two peaks of March to July and October to November in frequency.In regional distribution,the southern part of North China has the highest drought frequency and intensity,and strong(extreme and severe) North China regional meteorological drought events can be divided into six types,of which the whole North China type occurs more frequently.During the past 50 years,the North China regional drought events show an increase trend in both frequency and intensity,for which the main cause may be the obvious decrease of annual precipitation in this region,with the contribution of significant increase trend in temperature.