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CN 11-1768/O4

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BCC模式对北半球阻塞高压的模拟偏差评估及原因研究
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中国气象局国家气候中心

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国家重点研究计划2016YFA0602103, 2018YFE0196000


Reproductions of the Northern Hemisphere Blocking in BCC models
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National Climate Center, China Meteorological Administration

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    摘要:

    基于NCEP/NCAR、日本气象厅的JRA55以及欧洲中期预报中心(ECMWF)最新发布的ERA5三套逐日再分析资料数据,考察国家气候中心中等分辨率(全球近110km) 的气候系统模式BCC-CSM2-MR和单独大气模式BCC-AGCM3-MR对北半球中高纬度阻塞高压的模拟能力。再分析数据分析结果表明:“北大西洋-欧洲地区”以及“北太平洋中部地区”分别为北半球阻高发生的最高频及次高频区域;冬春季为阻高高发季节, 夏秋季阻高频率减少至冬春季的一半左右;ERA5中各个季节的阻高频率均高于另两套资料结果,尤其在北太平洋地区。模拟评估结果显示,单独大气模式BCC-AGCM3-MR对北半球中高纬度阻塞高压发生频率、空间分布和季节变化特征均有较好的模拟能力,其主要偏差表现为冬春欧亚大陆特别是乌拉尔山地区阻高频率偏高,而北大西洋地区阻高频率偏低;春季北太平洋阻高频率偏低。这与模式北半球高纬度地区500hPa位势高度场气候态偏差有关。BCC-CSM2-MR耦合模式的阻高模拟偏差总体与大气模式类似。但耦合模式中冬季欧亚大陆特别是乌拉尔山地区阻高频率减小、北太平洋春季阻高频率增大,模拟偏差减小。同时,耦合模式能够再现夏季北太平洋东西阻高频率双峰值特征。因此,海气耦合过程有助于改善对欧亚及北太平洋地区阻高频率模拟。阻高频率年际变率受到气候系统内部变率不确定性的较大影响,这也是制约阻高的预测水平的重要因素。

    Abstract:

    In this paper, performances of the median-resolution (about 110km) climate system model (BCC-CSM2-MR)and the atmospheric model (BCC-AGCM3-MR) developed in Beijing Climate Center are evaluated by three reanalysis datasets (ERA5, JRA55 and NCEP/NCAR). Results show that high blocking tendency can be distinguished over “North Atlantic-West Europe” and “Central North Pacific”. Winter and spring blocking frequency is almost twice of that in summer and autumn. Blocking frequency in ERA5 is higher than that in JRA55 and NCEP/NCAR, especially over the North Pacific. Model evaluations show that the atmospheric model can well reproduce the main features of Northern Hemisphere blocking frequency, spatial structures and seasonal variations. Main biases are the overestimation over Europe-Asia in winter and spring especially over Ural Mountains, as well as the underestimations over the North Atlantic. The biases are attributed to the climatological biases of geopotential height at 500hPa. General performances of BCC-CSM2-MR are similar to BCC-AGCM3-MR. But winter and spring blocking over Europe-Asia especially over Ural Mountains are improved. Spring blocking and the double-peak blocking structure in summer over the North Pacific are also better reproduced in the coupled model. Therefore, air-sea coupling may help to improve the blocking frequency reproduction over Europe-Asia and North Pacific. The internal variability of climate system has great impact on the variation of blocking frequency, which will also affect model capability in blocking high prediction.

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历史
  • 收稿日期:2019-10-18
  • 最后修改日期:2019-12-25
  • 录用日期:2020-01-17
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