双月刊

ISSN 1006-9895

CN 11-1768/O4

热带大气对流垂直结构与降水模拟偏差的关系:基于GAMIL3的分析
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作者单位:

1.中国科学院大气物理研究所;2.中国科学院大气物理研究所,中国科学院气候变化研究中心CCRC

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基金项目:

中国科学院“国际伙伴计划-国际大科学计划培育专项”项目“全球季风模拟研究国际计划”(资助号134111KYSB20160031)、第二次青藏科考项目 (STEP) (资助号2019QZKK0102)


Relationship between vertical convection structure and precipitation simulation bias in the tropical atmosphere: An analysis based on GAMIL3
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Affiliation:

The Institute of Atmospheric Physics, Chinese Academy of Sciences

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    摘要:

    针对 LASG/IAP 发展的大气环流模式 GAMIL2 (G2)和 GAMIL3(G3),评估了其对热带降水气候态以及对流垂直结构的模拟能力,在此基础上探究了新版本模式降水模拟改进的原因以及热带对流垂直结构与降水模拟偏差的关系。两个版本的GAMIL都较好地捕捉到了热带降水的主要特征,且G3的模拟结果整体优于G2。新版本的主要改进在于显著减小了热带西北太平洋正降水偏差。水汽收支诊断显示,模式降水偏差主要来源于蒸发项和水汽垂直平流动力项,而后者的偏差则来自于对流强度和对流垂直结构的共同作用。对流垂直结构偏差主要存在于赤道印度洋与赤道大西洋区域,表现为大气低层辐合分量偏小,对流卷出层高度偏高;在热带西北太平洋与赤道东太平洋区域,模式较好地还原了典型的“头重型”和“脚重型”对流垂直结构,但依然存在有整体性的对流偏深。湿静力能(MSE)收支显示,热带西北太平洋区域过量的净能量通量是模式垂直运动偏差的主要来源。而对流垂直结构偏深造成的总湿稳定度(gross moist stability,GMS)偏大,在一定程度上抵消了模式中的净能量通量偏差,抑制了模拟的对流强度。诊断结果显示,G3中热带西北太平洋区域的降水改善主要源于对流强度正偏差的减小。G3中对流阈值和层云阈值的下调,使得对流发生频率增加,从而抑制了过大的对流强度。热带对流垂直结构与降水偏差有着紧密且多样的联系,在未来模式发展中应当予以重视。

    Abstract:

    Based on the LASG/IAP developed general circulation model GAMIL2 (G2) and GAMIL3 (G3), the simulation ability of tropical precipitation and convective vertical structure was evaluated, and the reasons for the improvement of precipitation simulation and the relationship between the vertical structure of tropical convection and precipitation simulation deviations were explored. Both versions of GAMIL precisely capture the main characteristics of tropical precipitation, while G3’s simulation are globally accurate than G2. The main improvement of the new version is to significantly reduce the positive precipitation bias in the tropical northwest Pacific Ocean. The water vapor budget diagnosis shows that the precipitation deviation mainly come from the evaporation term and the vertical advection dynamic term, and the latter comes from the combined effect of intensity of vertical motion and the vertical motion profiles. The vertical structure deviation of convection mainly exists in equatorial Indian Ocean and equatorial Atlantic Ocean areas, which mainly corresponds to weaker convergence component in lower atmosphere and higher altitude of detrainment. In the tropical northwest Pacific and equatorial Eastern Pacific, the typical “top-heavy” and “bottom-heavy” characteristic of the vertical motion profile are well represented, but the deeper convection than reanalysis data is still eminent. The wet static energy (MSE) budget shows that the excess net energy flux over the tropical Northwest Pacific is the main source of the modeled vertical motion deviation. However, the deeper vertical convective structure results in a larger gross moist stability (GMS), which offset the net energy flux deviation and inhibited the simulated convective intensity. the significant improvement of precipitation simulation in the tropical northwest Pacific in G3 Is mainly due to the reduction of positive deviation of convective intensity. The down-regulation of convective threshold and stratus threshold in G3 increase the frequency of convection and inhibits excessive intensity of vertical motion. The vertical structure of tropical convection has various and close relationships with precipitation deviation, which should be paid more attention to in future model development.

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  • 收稿日期:2021-06-10
  • 最后修改日期:2021-09-15
  • 录用日期:2021-10-08
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