Title: Thermodynamic Constraints on the Size Distributions of Tropical Clouds

Abstract

Tropical convective clouds evolve over a wide range of temporal and spatial scales, which makes them difficult to simulate numerically. Here we propose that cloud statistical properties can be derived within a simplified time-independent coordinate system of cloud number n, saturated static energy h ^★, and cloud perimeter λ. Under the constraint that circulations around cloud edge compete with each other for total buoyant energy and air, we show that the product of cloud number and cloud perimeter nλ is invariant with λ and that cloud number follows a negative exponential with respect to cloud-edge deviations of h ^★; with respect to the mean. Overall, the summed perimeter of all clouds scales as the square root of the atmospheric static stability. These theoretical results suggest that the complexity of cloud field structures can be viewed statistically as an emergent property of atmospheric bulk thermodynamics. Comparison with a detailed tropical cloud field simulation shows general agreement to within ≤13%. For the sake of developing hypotheses about cloud temporal evolution that are testable in high resolution simulations, the shapes of tropical cloud perimeter distributions are predicted to be invariant as climate warms, although with a modest increase in total cloud amount.

Authors:

Garrett, Timothy J.  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-9277-8773"
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Glenn, Ian B.  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-3077-873X"
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Krueger, Steven K.  ^[1]

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• Search DOE PAGES for ORCID "0000-0002-3449-9351"
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+ Show Author Affiliations

1. Univ. of Utah, Salt Lake City, UT (United States)

Publication Date:

2018-07-23

Research Org.:

Univ. of Utah, Salt Lake City, UT (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1539761

Grant/Contract Number:  

SC0016282

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Geophysical Research: Atmospheres

Additional Journal Information:

Journal Volume: 123; Journal Issue: 16; Journal ID: ISSN 2169-897X

Publisher:

American Geophysical Union

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; Meteorology & Atmospheric Sciences