Convective environment in pre-monsoon and monsoon conditions over the Indian subcontinent: the impact of surface forcing
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Published:2018-05-30
Issue:10
Volume:18
Page:7473-7488
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ISSN:1680-7324
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Container-title:Atmospheric Chemistry and Physics
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language:en
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Short-container-title:Atmos. Chem. Phys.
Author:
Thomas Lois,Malap Neelam,Grabowski Wojciech W.,Dani Kundan,Prabha Thara V.
Abstract
Abstract. Thermodynamic soundings for pre-monsoon and monsoon seasons from the Indian
subcontinent are analysed to document differences between convective
environments. The pre-monsoon environment features more variability for both
near-surface moisture and free-tropospheric temperature and moisture
profiles. As a result, the level of neutral buoyancy (LNB) and pseudo-adiabatic
convective available potential energy (CAPE) vary more for the pre-monsoon
environment. Pre-monsoon soundings also feature higher lifting condensation
levels (LCLs). LCL heights are shown to depend on the availability of surface
moisture, with low LCLs corresponding to high surface humidity, arguably
because of the availability of soil moisture. A simple theoretical argument
is developed and showed to mimic the observed relationship between LCLs and
surface moisture. We argue that the key element is the partitioning of
surface energy flux into its sensible and latent components, that is, the
surface Bowen ratio, and the way the Bowen ratio affects surface buoyancy flux.
We support our argument with observations of changes in the Bowen ratio and
LCL height around the monsoon onset, and with idealized simulations of cloud
fields driven by surface heat fluxes with different Bowen ratios.
Publisher
Copernicus GmbH
Subject
Atmospheric Science
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