21世纪中国极端气温指数变化情况预估

Multi-Model Ensemble Prediction of Extreme Temperature Indices in China

利用政府间气候变化委员会资料中心的模式预测结果(IPCC-AR4),分析了在高(SRES A2)、中(SRES A1B)、低(SRES B1)3种不同的排放情景下中国未来21世纪极端气温变化特征。研究结果表明:随着全球变暖,中国区域极端气温指数的变化是一致的增加(减少)趋势。其中霜冻日数和温度年较差呈减少趋势,生长季指数、热浪指数和暖夜指数是增加趋势。在高排放(A2)情景下,中国地区各极端气温指数增加(减少)趋势最明显,低排放(B1)情景下极端气温指数变化趋势最小。在2075年前,极端气温指数在A1B情景下的变化幅度要大于A2情景下的变化,2075年之后,却与之相反。在各极端气温指数中,热浪指数(HWDI)和暖夜指数(TN90)上升趋势最为明显,其次是霜冻日数(FD)和生长季指数,气温年较差(ETR)变化最小。在空间分布的特征上,极端气温指数基本上保持一致的增加或减少的变化趋势(温度年较差除外),变化基本上是由北向南变化率逐渐增大,其中西北的极端指数变化率高于东北,只有暖夜指数的变化情况有所不同,在西南和华南地区出现了变化的大值区。

Using the results of IPCC-AR4 simulations, extreme temperature trends in China are analyzed under three different emissions scenarios SRES A2, SRES A 1B, and SRES B1. Results show that extreme temperature indices exhibit consistent trends throughout China. The indices of frost days （FD） and extreme temperature range （ ETR ） decrease, while increases occur for growing season length （ GSL）, warm nights （TN90） and heat wave duration index （HWDI）. In the high emissions scenario （A2）, index trends show the largest changes, and have the lowest amount of change in the low emissions scenario （B 1）. Changes in the five indices are more substantial in SRES A 1 B than in SRES A2 before the year 2075, in contrast to variations after that year. Among the extreme temperature indices, HWDI and TN90 have the largest increases. For SRES A2, the changes in heat wave duration index and warm nights are 90.2d/100a and 44.3 %/100a respectively, and the frost days and growing season length have the second largest changes, of - 42 days per decade and 28.1 days per decade, respectively, with the least change in ETR, which decreased 1.7℃ per decade. Zonal means indicate that during the period of 2021 2050, the smallest change in HWDI is an increase of 13.6 days in SRES B1, where ETR shows its largest change of - 0.4℃. The most significant variations in FD, GSL, HWD1 and TN90 are - 16.8 days, 17.2 days, 16.7 days and 14.7%, respectively, in the emissions scenarios of A1B, in which ETR has the smallest change of - 0.18℃. In the late 21st century （2071 to 2100）, HWD1 change is greatest with 72.8 days, but ETR has the smallest change of - 1.3℃, while other indices such as FD, GSL and TN90 have similar changes as in the high emissions scenario. Except for the index of growing season length, the spatial distributions of the other four indices＇ trends are almost the same throughout the whole country, with variability tending to increase gradually from northern to southern China. There are more marked changes in northwest China than northeast China for indices of FD, ETR and HWDI, as compared to TN90 which has larger changes in southwest and southern China.