RCPs情景下汉江流域未来极端降水的模拟与预估

采用应用于跨行业影响模式比较计划(ISIMIP)的5个CMIP5全球气候模式模拟的历史和未来RCP排放情景下的逐日降水数据,在评估模式对汉江流域1961—2005年极端降水变化特征模拟能力的基础上,进一步计算了RCP2.6、RCP4.5和RCP8.5排放情景下汉江流域未来2016—2060年极端降水总量(R95p)、极端降水贡献率(PEP)、连续5 d最大降水(RX5d)和降水强度(SDII),结果表明:RCP4.5情景下的极端降水指数上升最明显,R95p和RX5d分别较基准期增加12.5%和8.2%,PEP增加3.2个百分点,SDII微弱上升。在不同排放情景下,PEP均有一定的增幅,以流域西北和东南部增幅较大;R95p在流域绝大部分区域表现出一定的增加,且流域东南部和北部是增幅高值区;RX5d在RCP2.6和RCP4.5情景下整体表现为增加的特征,但在RCP8.5情景下整体表现为减少的特征。对极端降水预估的不确定性中,SDII的不确定性最小,RX5d的不确定性最大;不确定性大值区主要位于流域东部、东南部和西北部部分区域。

Projection of extreme precipitation in the Hanjiang River basin under different RCP scenarios

Based on the daily precipitation data with different RCP scenarios from the five global climate models (GCMs) in the Fifth phase of Coupled Model Intercomparison Project (CMIP5), also as the main models in the Inter-Sector Impact Model Intercomparison Project (ISIMIP), the frequency and intensity of extreme precipitation in the Hanjiang River basin in the period of 2016-2060 were analyzed with the indices maximum consecutive 5-day precipitation (RX5d), percentages of extreme precipitation in the annual total volume (PEP), annual total precipitation when daily precipitation greater than 95th percentile (R95p) and simple daily intensity index (SDII) under different scenarios. GFDL-ESM2M, the best GCM from the five, which is selected through the test of the simulation performance with the meteorological station data in the historical period of 1961-2005, was used to interpret the projection results. At the same time the other GCMs were also taken in the projection in order to show the uncertainty. The results are as follows. Under RCP4.5 scenario the extreme precipitation indices increase the most, in detail R95p, PEP and RX5day increase by 12.5%, 3.2 percentage points and 8.2% respectively, relative to the reference period of 1961-2005. SDII increases very slightly. PEP increases in all three RCP scenarios, especially more in the northwest and southeast of the basin area; R95p shows a certain amount of increase in the most basin area, while the southeastern and northern parts have more increase; RX5d increases under RCP2.6 and RCP4.5 scenarios, but it decreases under RCP8.5 scenario in general. As to the uncertainty of these four indices, SDII is the lowest, while RX5d is the highest. The regions with relatively higher projection uncertainty are mainly in the eastern, southeastern and northwestern parts of the basin.