摘要:主要评估了美国国家大气研究中心的NCAR CESM（Community Earth System Model，NCAR）和中国科学院的CAS ESM（Earth System Model，Chinese Academy of Sciences）两个地球系统模式对亚洲东部夏季气候态的模拟性能。使用NCAR CESM和CAS ESM各两种不同的水平分辨率，一共进行了4组长达19年（1998~2016年）的数值积分试验，并通过对2 m气温、降水强度和降水日变化等的分析，比较了这两个模式在亚洲东部的模拟性能。结果表明，CAS ESM和NCAR CESM均能模拟出夏季2 m气温和降水强度的大尺度分布特征，但整体上模拟得到的地表面气温偏暖、降水强度偏弱。对于降水日变化而言，观测的日降水峰值在陆地上主要发生在下午到傍晚时段，在海洋上则出现在午夜到凌晨时段。两组低分辨率试验模拟的陆地降水峰值出现过早，且无法模拟出四川盆地的夜间降水峰值和部分海洋地区凌晨或上午的降水峰值。提高分辨率对模式的模拟性能有显著的提升作用。高分辨率下，NCAR CESM和CAS ESM对陆地和海洋的降水日变化模拟性能都明显提高。对降水日变化的定量化分析表明，高分辨率CAS ESM模式对整个亚洲东部降水日变化的模拟最优。目前模式对海陆风的模拟还不太理想，未来要进一步提高模式模拟性能，需要重点完善与气温、降水过程相关的物理参数化方案。
关键词:CAS ESM (Earth System Model, Chinese Academy of Sciences)/
NCAR CESM (Community Earth SystemModel, NCAR)/
亚洲东部/
降水日变化
Abstract:This study evaluates the performance of two global models, i.e., the NCAR CESM (Community Earth System Model, NCAR) and the CAS ESM (Earth System Model, Chinese Academy of Sciences), for the simulation of boreal summer climate over eastern Asia. Four 19-year (1998-2016) AMIP (Atmospheric Model Intercomparison Project)-type experiments have been conducted using both the NCAR CESM and the CAS ESM with two different horizontal resolutions, and climatological means of 2-m air temperature, precipitation intensity and its diurnal cycle in the boreal summer over eastern Asia are analyzed. The results show that both models can reproduce large-scale features of boreal summer 2-m air temperature and precipitation intensity, although warm biases are found in the simulation of 2-m air temperature and precipitation rate is underestimated. For the diurnal cycle of precipitation, the observed peaks of precipitation occur during the afternoon to early evening over the land and during midnight to early morning over the ocean. Precipitation peaks earlier than observations over the land in the two coarse-resolution experiments, while the nocturnal peak in Sichuan Basin and the morning or early morning peak over some ocean areas cannot be reproduced. Increasing the horizontal resolution can significantly improve the model performance. The two high-resolution experiments distinctly improve the simulation of precipitation peaks over the land and ocean, and can well reproduce the afternoon peak over some islands. Quantitative comparisons between simulations of the two models indicate that the high-resolution CAS ESM experiment can yield the best simulation of precipitation peaks in the entire study region. The simulation of land and sea breezes still needs to be improved. Improvement of physical parameterizations related to precipitation and thermodynamic processes is very important for further improvement of the model performance.
Key words:CAS ESM (Earth System Model, Chinese Academy of Sciences)/
NCAR CESM (Community Earth System Model, NCAR)/
Eastern Asia/
Diurnal cycle of precipitation
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