EGU21-10490, updated on 04 Jan 2024
EGU General Assembly 2021
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Unsteady vortex behavior in the Asian monsoon anticyclone

Leong Wai Siu1 and Kenneth Bowman2
Leong Wai Siu and Kenneth Bowman
  • 1Department of Earth and Atmospheric Sciences, Cornell University, Ithaca NY, United States of America (
  • 2Department of Atmospheric Sciences, Texas A&M University, College Station TX, United States of America (

The Asian monsoon anticyclone (AMA), which is primarily driven by the latent heat released by monsoon precipitation, is one of the dominant features of the Northern Hemisphere summer circulation in the upper troposphere and lower stratosphere. Due to variations in the diabatic heating, interactions with Rossby waves propagating along the subtropical jet, and internal dynamics within the anticyclone, the circulation of the AMA is unsteady. Here we use the ERA-Interim dataset and trajectories computed with ERA-Interim winds to show that the AMA contains two or three distinct synoptic-scale subvortices 69% of the time, while a single circulation center is present only 23% of the time. More than three simultaneous subvortices are uncommon. Observed behaviors of the subvortices include 1) splitting of a single vortex into two vortices; 2) merger of two vortices into a single vortex; 3) vortex shedding in the eastward direction; 4) vortex shedding in the westward direction; and 5) formation, movement, and dissipation of a vortex. The evolution of the subvortices is closely tied to stirring and transport.

How to cite: Siu, L. W. and Bowman, K.: Unsteady vortex behavior in the Asian monsoon anticyclone, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10490,, 2021.

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