Bhowmick, M and Parker, DJ orcid.org/0000-0003-2335-8198 (2018) Analytical solution to a thermodynamic model for the sensitivity of afternoon deep convective initiation to surface Bowen ratio. Quarterly Journal of the Royal Meteorological Society, 144 (716). pp. 2216-2229. ISSN 0035-9009
Abstract
The tendency of convective rainfall to initiate over a wetter or drier land surface is a critical feedback process in the climate system, influencing the hydrological cycle on a variety of spatial scales, especially in parts of the world where water is limited. A simple algebraic solution is derived from fundamental physical equations, to predict the sign of this convective rainfall feedback with the surface. The tendency for convection to occur is evaluated by the rate at which the convective boundary layer top approaches the level of free convection.
Well-known integral models predict the rate of ascent of the boundary layer top, which tends to be faster over a dry surface. The associated changes in equivalent potential temperature in the boundary layer determine the rate at which the level of free convection descends, typically faster over a wet surface, as a function of the ambient profile, the thermodynamic forcing, and the surface Bowen ratio. The resulting system is controlled by three parameters. Two non-dimensional parameters determine whether there is wet or dry `advantage'; the Bowen ratio at the boundary layer top and a `convective instability parameter', defined as the ratio of the vertical gradient of saturated equivalent potential temperature at the level of free convection to the profile stability just above the boundary layer. A dimensional function, dependent on the surface fluxes, the boundary layer depth and the profile stability, provides the magnitude of the response. In comparison with previous work, the solution is both rigorously derived from physical principles, and encapsulated in a simple algebraic form. A first evaluation of the theoretical framework has been made using data from a convection-permitting numerical model simulation over India, and indicates that the equations successfully determine the conditions under which convection is triggered over dry surfaces.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2018 The Authors. Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of the Royal Meteorological Society. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/) |
Keywords: | Bowen ratio; convection; convective boundary layer; convective initiation; cumulonimbus; Land-atmosphere interaction; mixed-layer model; precipitation; rainfall |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst for Climate & Atmos Science (ICAS) (Leeds) |
Funding Information: | Funder Grant number Royal Society No External Reference NERC No External Refererence NERC NE/M003574/1 NERC NE/G018499/1 Met Office L0627 NERC NE/M017176/1 NERC NE/M020126/1 Met Office Not Known |
Depositing User: | Symplectic Publications |
Date Deposited: | 24 May 2018 11:11 |
Last Modified: | 18 Feb 2019 14:28 |
Status: | Published |
Publisher: | Wiley |
Identification Number: | 10.1002/qj.3340 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:131128 |
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