Data underlying the publication: Contributions of Arctic sea-ice loss and East Siberian atmospheric blocking to 2020 record-breaking Meiyu-Baiu rainfall - Simulations

<b>This is the primary data for a article going to be submitted to AGU GRL, named “contributions of Arctic sea-ice loss and East Siberian atmospheric blocking to 2020 record-breaking Meiyu-Baiu rainfall”. </b>We conducted atmospheric modeling experiments using the Community Atmosphere Model version 6 (CAM6), in the Community Earth System Model, version 2 (CESM2, Danabasoglu et al. 2020) from the National Center for Atmospheric Research (NCAR). The CAM6 was run with 1.25lon*0.9lat horizontal spacing, 32 vertical levels from the surface to 2.26 hPa. In the control experiment (CTL), 1995-2005 monthly climatological SST and SIC were used as the lower boundary condition and run for 75 years, including a 25-year spin-up. To examine the influence of Arctic sea ice anomalies, we further ran two perturbed experiments covering only the period from April 1^st to July 31^st. In the first perturbation experiment (ARCTIC), SST and SIC north of 65 were fixed to those of 2020 from May to July and to the climatology for April. The other perturbation experiment (GLOBAL) is the same as ARCTIC except it used the 2020 SST and SIC over the globe from May to July. We performed 20 ensemble simulations with slightly different initial conditions for each of the 4-month perturbation experiments and used their ensemble mean to reduce the internal variabilities. The GLOBAL-minus-CTL differences represent the atmospheric response to the SST and SIC anomalies in late spring-early summer of 2020, and the ARCTIC-minus-CTL differences represent the atmospheric response to the Arctic SIC and SST anomalies in late spring-early summer of 2020. <br><b>“2020mjjsic” denotes the ARCTIC experiment, “globalsst” denotes the GLOBAL experiment, and “ctrl_climatology” denotes the ensemble mean of CTL experiment.</b><br>Danabasoglu, G., Lamarque, J. F., Bacmeister, J., Bailey, D. A., DuVivier, A. K., Edwards, J., et al. (2020). The Community Earth System Model Version 2 (CESM2). Journal of Advances in Modeling Earth Systems,12, e2019MS001916.

本数据集为提交至美国地球物理学会（AGU）《地球物理研究快报》（GRL）的论文《北极海冰消退与东西伯利亚大气阻塞对2020年破纪录梅雨-日本梅雨降水的贡献》的核心原始数据。本研究使用美国国家大气研究中心（NCAR）的社区地球系统模型第2版（CESM2, Danabasoglu等, 2020）中的社区大气模型第6版（CAM6）开展大气模式试验。模式水平分辨率为1.25°经度×0.9°纬度，垂直方向共32层，覆盖从地表至2.26 hPa的大气区域。
控制试验（CTL）采用1995-2005年的逐月气候态海表温度（Sea Surface Temperature, SST）与海冰覆盖率（Sea Ice Concentration, SIC）作为下边界条件，连续积分75年，包含25年的自旋启动阶段。为探究北极海冰异常的影响，本研究额外开展了两个仅覆盖4月1日至7月31日时段的扰动试验。第一个扰动试验（ARCTIC）中，65°N以北区域的海表温度与海冰覆盖率在4月沿用气候态数值，5-7月则固定为2020年的观测值。第二个扰动试验（GLOBAL）与ARCTIC试验设置一致，仅将全球范围的海表温度与海冰覆盖率在5-7月替换为2020年的观测值。
针对这两个4个月时段的扰动试验，本研究共开展20组初值略有差异的集合模拟，并取集合平均以削弱内部变率的影响。其中，GLOBAL试验与CTL试验的差值可表征2020年晚春-初夏海表温度与海冰异常的大气响应，ARCTIC试验与CTL试验的差值则可表征2020年晚春-初夏北极海冰与海表温度异常的大气响应。
本数据集中，"2020mjjsic"对应ARCTIC试验，"globalsst"对应GLOBAL试验，"ctrl_climatology"对应CTL试验的集合平均结果。
Danabasoglu, G., Lamarque, J. F., Bacmeister, J., Bailey, D. A., DuVivier, A. K., Edwards, J. 等. (2020). 社区地球系统模型第2版（CESM2）. 《地球系统模式进展期刊》, 12, e2019MS001916.