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Non-uniqueness in a Single Column Model for Moist Convection

Turner, M.R. and Norbury, J. (2019) Non-uniqueness in a Single Column Model for Moist Convection Journal of the Atmospheric Sciences.

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We investigate a moist atmospheric column convection model by considering the atmosphere as a single vertical column of air parcels, each of which contains water vapour. The moist convective adjustment of both air and water mass in the column is considered from an (unstable) initial state to a statically stable final configuration of parcels. Two variations of an algorithm based upon swapping neighbouring parcels are compared: after swapping, no parcels remain supersaturated. The results of these algorithms are compared directly with those of the adjustment algorithm of Cheng et al. 2017 (Q. J. R. Meteorol. Soc. 143(708) p. 2925-2939) which adjusts an atmospheric column to achieve the global maximum of a relevant cost functional. Two examples are considered: in the first,the algorithms adjust to similar arrangements, showing that the global maximum of the functional is the dynamically preferred state, while in the second, the algorithms adjust to significantly different states. Thus we identify a non-uniqueness to the solution to the adjustment problem in terms of local and global cost functional maximisers. We then discuss the relevance of this nonuniqueness to numerical prediction in weather and climate models.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Mathematics
Authors :
Norbury, J.
Date : 2019
Copyright Disclaimer : © Copyright 2019 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act or that satisfies the conditions specified in Section 108 of the U.S. Copyright Act (17 USC §108) does not require the AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, requires written permission or a license from the AMS. All AMS journals and monograph publications are registered with the Copyright Clearance Center ( Questions about permission to use materials for which AMS holds the copyright can also be directed to Additional details are provided in the AMS Copyright Policy statement, available on the AMS website (
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Depositing User : Clive Harris
Date Deposited : 05 Dec 2019 13:51
Last Modified : 05 Dec 2019 13:51

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