摘要:利用东亚地区逐日降水资料，评估了17个CMIP5气候模式对中国东部夏季不同强度降水的时空分布、不同强度降水对1970年代末中国东部夏季总降水量年代际转折的贡献的模拟能力。从夏季不同强度降水占总降水的比重来看，在中国东北和华北地区，小雨和中雨占主导；而在华南和江淮地区，大雨和暴雨则相对更为重要。CMIP5模式可大致模拟出中国东部小雨、大雨和暴雨占总降水比重的空间分布，但对中雨占比的空间分布模拟较差。总体说来，多数CMIP5模式高估了小雨和中雨的比重，但低估了大雨和暴雨的比重，从而导致大多数模式高估东北和华北的总降水量，而低估华南和江淮的总降水量。对1970年代末我国华北和江淮地区夏季降水量的年代际转折，观测资料表明该转折主要体现为大雨和暴雨雨量的年代际转折；仅有少数CMIP5模式能模拟出华北大雨和暴雨年代际减少的特征，使得这些模式对华北地区总降水的年代际变化也有较好的模拟能力。对于江淮区域，由于大雨和暴雨的比重被严重低估，尽管部分模式能模拟出夏季总降水量年代际增加的特征，但却多以小雨、中雨的年代际变化为主。多模式集合并不能显著提高模式对不同强度降水的空间分布的模拟能力，尤其是降水年代际变化的模拟能力。
关键词:CMIP5模式/
降水强度/
年代际变化/
模式评估
Abstract:The capabilities of 17 CMIP5 models for simulating the intensity distribution of summer rainfall over eastern China are evaluated based on daily observational data. The decadal changes of rainfall with different intensities in the later 1970s and their relative contributions to the decadal change in total rainfall for both observation and model simulations are further analyzed and compared. Observations indicate that the total rainfall is mainly composed of light and medium rainfall over northern and northeastern China, while heavy rainfall account for a large proportion of the total rainfall over southern China and the Yangtze-Huai River basin (YHRB). In general, the CMIP5 models are able to capture the observed spatial distribution of proportion of light and heavy rainfall to total rainfall amount in Eastern China, except for medium rainfall. Most models have a bias toward an overestimation of the light and medium rainfall events, and an underestimation of heavy rainfall events. Therefore, these models overestimate the amount of total rainfall over northern and northeastern China and underestimate the amount of total rainfall over southern China and the YHRB. Our analysis indicates that the observed decadal changes in total rainfall over northern China and the YHRB in the late 1970s are mainly attributed to changes in heavy rainfall events. Over northern China, a few CMIP5 models reproduced the observed decadal decrease in both heavy rainfall and total rainfall. Over the YHRB, several models can reproduce the observed decadal increase in total rainfall. However, these models failed to reproduce the increase in heavy rainfall amount due to the model bias of a severe underestimation of heavy rainfall. The authors also find out that multi-model ensemble technique cannot significantly improve the model performance in simulating the spatial distribution of rainfall intensity, especially its decadal changes.
Key words:CMIP5 models/
Precipitation intensity/
Decadal variability/
Model evaluation
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