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Impact of Dust-Cloud-Radiation-Precipitation Dynamical Feedback on Subseasonal-to-Seasonal Variability of the Asian Summer Monsoon in Global Variable-Resolution Simulations With MPAS-CAM5
Frontiers in Earth Science ( IF 2.9 ) Pub Date : 2020-05-27 , DOI: 10.3389/feart.2020.00226
William K. M. Lau , Kyu-Myong Kim , Chun Zhao , L. Ruby Leung , Sang-Hun Park

In this study, we investigate the effects of increased dust emission from the Middle East deserts on subseasonal-to-seasonal (S2S) variability of the Asian summer monsoon (ASM). Numerical experiments are performed using the Model for Prediction Across Scales (MPAS) coupled with the Community Atmosphere Model (CAM5) physics, with regional refinement at 30 km grid resolution over South Asia and the surrounding regions. Result shows that increased dust emission and transport from the Middle East/West Asia region induces a strong dust-cloud-radiation-precipitation-circulation feedback, resulting in a colder surface over the desert regions and the western Tibetan Plateau, but warmer and moister troposphere with enhanced cloudiness and precipitation over the Pakistan/Northwest India (PNWI) region. The latter changes are amplified by the dust aerosol induced Elevated Heat Pump (EHP) mechanism along the West Himalayas/Iranian Plateau foothill regions, most pronounced during May-June. During July-August, cloud radiation feedback further enhances the warming of the upper troposphere, and cooling of the land surface over the PNWI and adjacent regions over West Asia. The upper tropospheric heating and increased precipitation over PNWI spur a large-scale anomalous Rossby wavetrain and a northward displacement of the subtropical jetstream, manifesting in a contraction of the South Asian High and westward shift of the Western Pacific Subtropical High. As a result, the entire ASM precipitation-cloud system is displaced westward. Precipitation and cloudiness are intensified over northwest and western India and west Asia, but suppressed over southern and central East Asia. Analyses of the S2S variability of the upper level vorticity balance suggests that heating by Middle East dust plays an important role in exciting, and anchoring a teleconnection pattern through interactions among dust-cloud radiation, precipitation heating over the PNWI, the development of an upper level Rossby wavetrain, and the northward shift of the boreal summer jetstream over Eurasia.



中文翻译:

在使用MPAS-CAM5进行的全球可变分辨率模拟中,粉尘云辐射-降水动态反馈对亚洲夏季风的季节变化和季节变化的影响。

在这项研究中,我们调查了来自中东沙漠的粉尘排放量增加对亚洲夏季风(ASM)的亚季节到季节(S2S)变异性的影响。使用跨尺度预测模型(MPAS)结合社区大气模型(CAM5)物理进行了数值实验,并在南亚及周边地区以30 km的网格分辨率对区域进行了改进。结果表明,来自中东/西亚地区的粉尘排放和运输量增加,引起强烈的粉尘云辐射-降水-循环反馈,导致沙漠地区和青藏高原西部的地表较冷,而对流层变暖和潮湿巴基斯坦/印度西北(PNWI)地区的多云和降水增加。后者的变化通过西喜马拉雅山/伊朗高原山麓地区的粉尘气溶胶诱导的高热泵(EHP)机制得到放大,在5月至6月期间最为明显。在7月至8月期间,云辐射反馈进一步增强了对流层上方的变暖,以及PNWI和西亚附近地区的陆地表面变冷。对流层上层的高层对流层加热和增加的降水刺激了大规模的异常罗斯比波列和副热带高压气流的北移,表现为南亚高压的收缩和西太平洋副热带高压的西移。结果,整个ASM降水云系统向西移动。印度西北部和西部以及西亚的降水和阴霾加剧,但在南亚和中亚东亚地区受到镇压。对高层涡旋平衡的S2S变异性的分析表明,中东尘埃的加热在激发中起着重要作用,并通过尘埃云辐射,PNWI上的降水加热,高层的发展之间的相互作用来固定遥相关模式罗斯比(Rossby)波列和北欧夏季喷流的北移。

更新日期:2020-06-19
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