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基于可变分辨率地球系统模式的海河流域极端降水变化预估

Projected Changes in Extreme Precipitation over Haihe River Basin Based on a Variable-Resolution Community Earth System Model

  • 摘要: 基于1976~2005年格点化气候观测数据CN05.1,评估了均匀分辨率地球系统模式(UN-CESM)和可变分辨率地球系统模式(VR-CESM)对海河流域气候态降水和极端降水的模拟能力,分析了VR-CESM在RCP8.5情景下2021~2050年海河流域极端降水的变化。结果显示,相比UN-CESM分辨率1°(纬度)×1°(经度),VR-CESM海河流域分辨率0.125°(纬度)×0.125°(经度)弥补了全球模式在流域尺度模拟分辨率偏低的不足,模拟效果整体得到提高,对海河流域西南部和燕山南部的强降水频率、东部平原北部的强降水强度模拟的准确性有明显改进。与基准期(1976~2005年)相比,海河流域2021~2050年年降水量表现为北部以减少为主,中部和南部普遍增加;海河流域东南部7月降水量普遍增加10%以上。极端强降水频率以38°N为界,呈北部减少南部增加趋势;南部四省(河北省、河南省、山西省和山东省)交界地区强降水频率增加在20%以上;强降水量和强降水强度在北京东部和天津北部增幅最大,连续5日最大降水量在北京北部、太行山山前平原中部和山东、河北与河南三省交界处增加最多,较基准期增加80%以上。从预估的年降水量、强降水频率和强度变化发现,海河流域极端降水风险存在较大时空异质性,未来应对海河流域极端降水的复杂性将增加。

     

    Abstract: The simulation capabilities of the Uniform Resolution Community Earth System Model (UN-CESM) and Variable-Resolution Community Earth System Model (VR-CESM) for climatological precipitation and extreme precipitation in the Haihe River Basin (HRB) during 1976–2005 were evaluated using the daily gridded climate observation dataset CN05.1. Further analysis was conducted on the spatial and temporal characteristics of extreme precipitation over the HRB based on the VR-CESM precipitation estimation under the RCP8.5 scenario for 2021–2050. Compared with those of UN-CESM resolution: 1°(latitude)×1°(longitude), the results of VR-CESM compensate for the low resolution of global models in watershed scale simulations. The overall simulation effect is also improved. VR-CESM resolution in HRB: 0.125°(latitude)×0.125°(longitude) shows an enhanced accuracy in simulating the frequency of extreme precipitation in the southwestern part of the HRB and southern Yanshan and the intensity of extreme precipitation in the northern part of the eastern plain. With 1976–2005 as the base period, VR-CESM projects that the annual precipitation will decrease in the northern part of the HRB and increase in the central and southern regions of the HRB during 2021–2050. The precipitation in the southeastern HRB will generally increase by more than 10% in July. The projected frequency of heavy precipitation is bounded by 38° N and shows a decreasing trend in the north and an increasing trend in the south, with almost a 20% increase in the border area of the four southern provinces (Hebei, Henan, Shanxi, and Shandong Province). The projected increases in the maximum precipitation for 5 consecutive days mostly occur in the northern part of Beijing, the central parts of the Taihang Piedmont Plain, and the border regions of Shandong, Hebei, and Henan provinces, with the increasing magnitude of RX5day larger than 80% compared with the baseline period. The results for the precipitation, frequency, and intensity of extreme rainfall indicate significant spatiotemporal heterogeneity in the risk of extreme rainfall in the HRB, implying the potential complexity of dealing with extreme precipitation in the HRB in the future.

     

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