全球升温1.5℃与2.0℃情景下长江中下游地区极端降水的变化特征

基于长江中下游地区1961~2100年区域气候模式COSMO-CLM(CCLM)模拟与1961~2005年气象站观测的逐日降水数据,通过统计计算年降水量、强降水量、暴雨日数和极端降水贡献率4个极端降水指数,研究全球升温1.5℃与2.0℃情景下,长江中下游地区极端降水的时空变化特征。结果表明:(1)全球升温1.5℃情景下,年降水量相对于1986~2005年减少5%,强降水量、暴雨日数和极端降水贡献率分别增加7%、33%和4%;概率密度曲线表明,年降水量均值下降,强降水量、暴雨日数和极端降水贡献率均值上升,极端降水方差增大;年降水量、强降水量和暴雨日数在空间上表现为南部增加北部减少,极端降水贡献率则相反。(2)全球升温2.0℃情景下,年降水量下降3%,强降水量、暴雨日数和极端降水贡献率分别上升15%、46%和15%;年降水量均值稍有减少且方差稍有上升,强降水量、暴雨日数和极端降水贡献率均值和方差明显增加;年降水量减少区域位于长江主干以北,强降水量、暴雨日数和极端降水贡献率表现为绝大部分地区增加的空间变化特征。(3)全球升温由1.5℃至2.0℃时,年降水量、强降水量、暴雨日数和极端降水贡献率分别增加3%、7%、10%和11%;随升温幅度的增加极端降水均值和方差上升;极端降水呈增加态势的范围扩大。因此,努力将升温控制在1.5℃对降低极端降水的影响具有重要意义。

VARIATIONS OF THE EXTERME PRECIPITATION UNDER THE GLOBAL WARMING OF 1.5 ℃ AND 2.0 ℃ IN THE MID-LOWER REACHES OF THE YANGTZE RIVER BASIN

Based on the daily precipitation data of a high-resolution regional climate model (COSMO model in Climate Mode,CCLM) simulated for the period 1961-2100 and the 90 meteorological stations observed during 1961-2005 over the mid-lower reaches of the Yangtze River Basin,four typical extreme precipitation indices,i.e.annual precipitation,intensive precipitation,heavy rain days,and contribution ratio of intensive precipitation,were calculated separately.The spatiotemporal variations of extreme precipitation under the global warming of 1.5 ℃ and 2.0 ℃ were analyzed in detail.The results showed that:(1) In the 1.5 ℃ warming period,annual precipitation in the mid-lower reaches of the Yangtze River Basin will decrease by 5％,but intensive precipitation,heavy rain days,and contribution ratio of intensive precipitation will increase by 7％,33％ and 4％,respectively,relative to the reference period (1986-2005).The probability density curves showed that under the global warming of 1.5 ℃,the mean value of annual precipitation will decrease,but intensive precipitation,heavy rain days,and contribution ratio of intensive precipitation will increase,and the variances of extreme precipitation will increase,relative to the reference period.Compared with extreme precipitation in the reference period,the spatial distribution of annual precipitation,intensive precipitation,and heavy rain days show an increasing trend in the southem part of the mid-lower reaches of the Yangtze River Basin and a decreasing trend in the northern part,however,contribution ratio of intensive precipitation has the opposite result in the 1.5℃ warming period.(2) In the 2.0℃ warming period,annual precipitation will decrease by 3％,but intensive precipitation,heavy rain days,and contribution ratio of intensive precipitation will increase by 15％,46％ and 15％,respectively,relative to the reference period.The probability density curves showed that under the global warming of 2.0℃,The mean value and variance of annual precipitation will decrease and increase respectively,but intensive precipitation,heavy rain days,and contribution ratio of intensive precipitation will increase significantly,relative to the reference period.The region of annual precipitation reduction is located in the north of the mid-lower reaches of the Yangtze River Basin,but intensive precipitation,heavy rain days,and contribution ratio of intensive precipitation show that extreme precipitation will increase in most areas.(3)With a global warming of 1.5 ℃ to 2.0℃,annual precipitation,intensive precipitation,heavy rain days,and contribution ratio of intensive precipitation will increase by 3％,7％,10％ and 11％,respectively,relative to the reference period.The mean values and variances of extreme precipitation are projected to increase with the rising of temperature,by analyzing the probability density curves.The area and scope of extreme precipitation with increasing trend in a 2.0℃ warming will expand to larger than that of the extreme precipitation with same reference period in a 1.5 ℃ warming.Aforementioned findings revealed that compared to the extreme precipitation in a 2.0 ℃ warming,the temperature will be controlled strenuously at 1.5 ℃ warming that is of great significance to reduce the adverse effects of extreme precipitation.