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

William K.M. Lau, Kyu Myong Kim, Chun Zhao, L. Ruby Leung, Sang Hun Park

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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.

Original languageEnglish
Article number226
JournalFrontiers in Earth Science
Publication statusPublished - 2020 Jun 19

Bibliographical note

Funding Information:
Funding. This work was supported by the U.S. Department of Energy (DOE), Office of Science, Biological and Environmental Research as part of the Regional and Global Modeling and Analysis program area, including Grant Award #300426-00001 to U. of Maryland from the Pacific Northwest National Laboratory (PNNL). PNNL is operated for DOE, by Battelle Memorial Institute under contract DE-AC05-76RL01830. CZ was supported by the Fundamental Research Funds for the Central Universities of China and the National Natural Science Foundation of China (grant 41775146). Most of this work was completed while he was a research scientist at PNNL.

Publisher Copyright:
© Copyright © 2020 Lau, Kim, Zhao, Leung and Park.

All Science Journal Classification (ASJC) codes

  • Earth and Planetary Sciences(all)


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