Title: Evolution of Idealized Vortices in Monsoon-Like Shears: Application to Monsoon Depressions

Abstract

Abstract This study examines processes fundamental to the development of South Asian monsoon depressions using an array of integrations of an idealized convection-permitting numerical model. In each integration, a wave of initially small amplitude is subjected to a different amount of vertical and meridional wind shear, with temperature and moisture fields constructed according to realistic constraints. Based on the evolution of this disturbance into monsoon depression–like vortices, two features of the background environment emerge as important: the low-level gradient of moist static energy (MSE) and the low-level meridional shear. As the low-level MSE gradient steepens, the disturbance becomes stronger and produces more rain. This strengthening results from the interaction of the vortex with latent heat release by convection that is in turn organized by positive MSE advection in the northerly flow west of the vortex. In this region of advection, moister air from the north ascends along upward-sloping isentropes, driving moist convection. The disturbance also becomes stronger with increasing meridional shear, which makes the environment more barotropically unstable. The absence of either of these two features of the background environment prevents substantial growth of the disturbance. Our results suggest that monsoon depression growth in South Asia is fostered by themore » coexistence of a strong low-level MSE gradient with strong meridional wind shear associated with the monsoon trough.« less

Authors:

Diaz, Michael ^[1]; Boos, William R. ^[2]

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+ Show Author Affiliations

1. a Department of Earth and Planetary Science, University of California, Berkeley, Berkeley, California
2. a Department of Earth and Planetary Science, University of California, Berkeley, Berkeley, California, b Climate and Ecosystem Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California

Publication Date:

Thu Apr 01 00:00:00 EDT 2021

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

2217394

Alternate Identifier(s):

OSTI ID: 1864539

Grant/Contract Number:  

AC02-05CH11231; SC0019367

Resource Type:

Published Article

Journal Name:

Journal of the Atmospheric Sciences

Additional Journal Information:

Journal Name: Journal of the Atmospheric Sciences Journal Volume: 78 Journal Issue: 4; Journal ID: ISSN 0022-4928

Publisher:

American Meteorological Society

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; Asia; baroclinic flows; convection; cyclogenesis; cyclolysis; monsoons; mesoscale models