Improving the simulation of East Asian summer monsoon with mesoscale enhancement in an AGCM
Improving the simulation of East Asian summer monsoon with mesoscale enhancement in an AGCM
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通过 AGCM 的中尺度增强改进东亚夏季风的模拟
DOI：
10.1007/s00382-018-4580-x
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发表时间：
2019-07-01
期刊：
影响因子：
4.6
通讯作者：
Deng, Weitao
中科院分区：
文献类型：
--
作者：
Li, Zhongxian;He, Ping;Deng, Weitao
本文对美国国家大气研究中心社区大气模式第5版（CAM 5）中的海表湍流热通量参数化进行了改进，加入了中尺度对流运动的贡献（即，中尺度增强）。利用1979年1月至2015年12月的SST强迫试验进一步探讨了中尺度增强对东亚夏季风环流模拟的影响。试验表明，标准CAM 5模式对东亚夏季风系统的模拟存在明显的偏差。如东亚低纬850 hPa西风带偏弱，孟加拉湾、南海和热带西太平洋降水偏少，南亚和西太平洋副热带高压偏弱，东亚低纬对流层中上层偏冷等。通过在CAM 5中包括中尺度增强，这些偏差明显减少。例如，模拟的孟加拉湾夏季平均降水量从9.85毫米/天增加到11.76毫米/天，这更接近于观测值13.80毫米/天。进一步的分析表明，东亚夏季风降水和环流的改善是由于中尺度增强引起的对流增强和热带西太平洋水汽蒸发的增加。相应地，大气中的水汽凝结潜热也增加，对流层中上部的冷偏差减小。与此同时，中高层大气位势高度升高，使得东亚夏季风环流的重要组成部分南亚和西太平洋副热带高压的模拟强度更接近实际。
In this study, the parameterization of sea surface turbulent heat flux in National Center for Atmospheric Research Community Atmosphere Model version 5 (CAM5) is improved by including the contribution of mesoscale convective motion (i.e., mesoscale enhancement). The effect of mesoscale enhancement on the simulation of the East Asian summer monsoon circulation is further explored with SST-forced experiments that are conducted for the period of January 1979 to December 2015. Experiments suggest that the standard CAM5 exhibits evident biases in simulating the East Asian summer monsoon system. For example, the simulated westerlies at 850 hPa in low latitude of East Asia are too weak, the precipitations in the Bay of Bengal, the South China Sea, and the tropical western Pacific are underestimated, the simulated south Asia and western Pacific subtropical highs are too weak, and the upper and middle troposphere in the low latitudes of East Asia is too cold. By including the mesoscale enhancement in CAM5, these biases are clearly reduced. For example, the simulated summer mean precipitation in the Bay of Bengal is increased from 9.85 to 11.76 mm/day, which is closer to the observed value of 13.80 mm/day. Further analyses show that the improvements in the East Asian summer monsoon precipitations and circulations can be attributed to the enhancement of convections and the increase in water evaporation in the tropical western Pacific Ocean induced by mesoscale enhancement. Correspondingly, the latent heat due to vapor condensation in the atmosphere also increases, which reduces the cold bias in the mid-upper troposphere. Meanwhile, the geopotential height of the upper-middle-level atmosphere is elevated, which makes the simulated intensity of the south Asian and the western Pacific subtropical highs, two important components of the East Asian summer monsoon circulation, closer to the reality.