中国极端低温事件特征及其耕地暴露度研究

The characteristics of extreme minimum temperature events and exposure of farmland in China

基于中国543个气象站1960-2014年逐日最低气温数据,采用强度-面积-持续时间(Intensity-AreaDuration,IAD)方法,根据极端低温事件在时间上的发展和空间上的连续性特点,分析中国不同持续时间的区域性极端低温事件的强度和影响面积特点,评估极端低温事件对耕地面积的影响。结果表明:(1)气象站极端低温事件发生次数较多的地区主要位于华北及东北地区,以短期(持续时间1~2日)事件为主,西北及东南等地的极端低温事件次数较少,但多为中期(持续时间3~5日)、长期(持续时间6日以上)事件;(2)21世纪之前,区域性极端低温事件持续时间相对较短、但强度和影响面积较大;进入21世纪,极端低温事件的影响面积和强度有所减小,但持续时间增加;(3)极端低温事件影响的耕地面积在1969年之前为上升趋势,随后下降,进入21世纪,极端低温事件影响的耕地面积无明显变化。

Based on daily minimum temperature data from 543 meteorological stations from 1960 to 2014, characteristics of extreme minimum temperature events over China were analyzed. By taking the spatial and temporal continuity characteristics of extreme minimum temperature events into account, the Intensity-Area-Duration （lAD）method was applied to assess the relationship between intensity and coverage of extreme minimum temperature events at different durations and evaluate the area of farmland exposed to extreme minimum temperature events. We found that the areas where single-site extreme minimum temperature events occur more frequently are located in the northern and northeastern regions and that most events last 1-2 days. In northwestern and southeastern areas, where extreme minimum temperature events are comparatively lesser, most events last longer （last 3-5 days, or more than six days）. Coverage of extreme minimum temperature events has decreased from the 1960s to 1990s, and increased in the 21st century. The coverage of extreme minimum temperature events was lowest in the 1990s for different durations. Before the 21st century, regional extreme minimum temperature events were of short duration but greater area and intensity. Since the beginning of the 21st century, both the coverage and intensity of extreme minimum temperature events has decreased, but the duration has increased. The area of farmland exposed to extreme minimum temperature events increased before 1969, but then decreased. The maximum and minimum farmland area exposed to extreme minimum temperature events was in 1969 and 2007 respectively. Farmland area exposed to extreme minimum temperature events has stabilized since the beginning of the 21 st century.