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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2018-1
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
08 Jan 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Convective environment in pre-monsoon and monsoon conditions over the Indian subcontinent: the impact of surface forcing
Lois Thomas1, Neelam Malap1, Wojciech W. Grabowski2,3, Kundan Dani1, and Thara V. Prabhakran1 1Indian Institute of Trropical Meteorology, Pune, India
2National Center for Atmospheric Research, Boulder, Colorado, USA
3Institute of Geophysics, Faculty of Physics, University of Warsaw, Warsaw, Poland
Abstract. Thermodynamic soundings for premonsoon and monsoon seasons from the Indian subcontinent are analyzed to document differences between convective environments. Pre-monsoon environment features more variability for both near surface moisture and free-tropospheric temperature and moisture profiles. As a result, 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 LCL 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 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.
Citation: Thomas, L., Malap, N., Grabowski, W. W., Dani, K., and Prabhakran, T. V.: Convective environment in pre-monsoon and monsoon conditions over the Indian subcontinent: the impact of surface forcing, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2018-1, in review, 2018.
Lois Thomas et al.
Lois Thomas et al.
Lois Thomas et al.

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Short summary
Thermodynamic parcel analysis of several high resolution soundings from Pune, India investigating the pre-monsoon and monsoon conditions is carried out in this study. A simple theoretical approach for cloud base height estimation is illustrated. Results illustrate the role of surface forcing in contrasting conditions of premonsoon and monsoon. Both Large eddy simulation, observational data and theoretical explanation are presented.
Thermodynamic parcel analysis of several high resolution soundings from Pune, India...
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