Moisture‐radiative cooling instability

Details

Serval ID
serval:BIB_EC2DA3A2108A
Type
Article: article from journal or magazin.
Collection
Publications
Title
Moisture‐radiative cooling instability
Journal
Journal of Advances in Modeling Earth Systems
Author(s)
Beucler Tom, Cronin Timothy W.
ISSN
1942-2466
1942-2466
Publication state
Published
Issued date
12/2016
Peer-reviewed
Oui
Volume
8
Number
4
Pages
1620-1640
Language
english
Abstract
Radiative-convective equilibrium (RCE)—the statistical equilibrium state of the atmosphere where convection and radiation interact in the absence of lateral transport—is widely used as a basic-state model of the tropical atmosphere. The possibility that RCE may be unstable to development of large-scale circulation has been raised by recent modeling, theoretical, and observational studies, and could have profound consequences for our understanding of tropical meteorology and climate. Here, we study the interaction between moisture and radiative cooling as a contributor to instability of RCE. We focus on whether the total atmospheric radiative cooling decreases with column water vapor; this condition, which we call moisture-radiative cooling instability (MRCI), provides the potential for unstable growth of moist or dry perturbations. Analytic solutions to the gray-gas radiative transfer equations show that MRCI is satisfied when the total column optical depth—linked to column water vapor—exceeds a critical threshold. Both the threshold and the growth rate of the instability depend strongly on the shape of the water vapor perturbation. Calculations with a realistic radiative transfer model confirm the existence of MRCI for typical tropical values of column water vapor, but show even stronger dependence on the vertical structure of water vapor perturbation. Finally, we analyze the sensitivity of atmospheric radiative cooling to variability in column water vapor in observed tropical soundings. We find that clear-sky MRCI is satisfied across a range of locations and seasons in the real tropical atmosphere, with a partial growth rate of ∼1 month.
Keywords
water vapor, radiation, instability, tropical meteorology, clouds, climate
Web of science
Open Access
Yes
Create date
21/02/2023 15:36
Last modification date
25/10/2023 14:44
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