EGU2020-4341, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-4341
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Effects of the Tibetan Plateau on East Asian Summer Monsoon via Weakened Transient Eddies

Qiaoling Ren1, Song Yang1, Xinwen Jiang2, Yang Zhang3, and Zhenning Li4
Qiaoling Ren et al.
  • 1Sun Yat-sen University, School of Atmospheric Sciences, China (renql@mail2.sysu.edu.cn)
  • 2Institute of Plateau Meteorology, China Meteorological Administration, Chengdu, China
  • 3School of Atmospheric Sciences, Nanjing University, Nanjing, China
  • 4Institute of Environment, Energy and Sustainability, Chinese University of Hong Kong, Hong Kong, China

Previous studies have revealed that the Tibetan Plateau (TP) can weaken the high-frequency and low-frequency transient eddies (TE) transported along the westerly jet. Here the effects of TP on East Asian summer monsoon via weakened TE are investigated based on the simulations by the NCAR Community Earth System Model, in which a nudging method is used to amplify the TP’s inhibition of TE without changing the steady dynamic and thermodynamic effects of TP. Results reveal that the weakened TE by TP weaken the East Asian westerly jet (EAWJ) and shift the jet southward via transient vorticity flux. The southward EAWJ accompanied with reduced poleward transport of moisture by TE results in less rainfall in northern East Asia but more rainfall in southern East Asia, particularly in early summer when the EAWJ is stably located over the TP and the meridional gradient of water vapor is large. Furthermore, the anomalous precipitation can move the EAWJ further southward through the anomalous diabatic heating in early summer, forming a positive feedback. Therefore, the TP’s inhibition of TE can shift the East Asian rain belt southward, different from the TP’s steady forcing which favors a poleward shift of the rain belt. It is also demonstrated that the atmospheric internal variability can lead to the south-flood-north-drought pattern of summer rainfall change over East Asia, indicating the important role of TE in East Asian summer monsoon.

How to cite: Ren, Q., Yang, S., Jiang, X., Zhang, Y., and Li, Z.: Effects of the Tibetan Plateau on East Asian Summer Monsoon via Weakened Transient Eddies, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4341, https://doi.org/10.5194/egusphere-egu2020-4341, 2020

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Presentation version 1 – uploaded on 30 Apr 2020
  • CC1: Comment on EGU2020-4341, Bernard Legras, 04 May 2020

    Is there a relation between what you are showing and the quasi-biweekly variability of the Asian monsoon?

    • AC1: Reply to CC1, Qiaoling Ren, 05 May 2020

      Thanks for your attention. Yes, there is. The atmospheric variations that we have reduced in model include quasi-biweekly variability.