Open AccessUnderstanding the Response of Tropical Ascent to Warming Using an Energy Balance Framework
Author(s) -
Jenney A. M.,
Randall D. A.,
Branson M. D.
Publication year - 2020
Publication title -
journal of advances in modeling earth systems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.03
H-Index - 58
ISSN - 1942-2466
DOI - 10.1029/2020ms002056
Subject(s) - convection , mass flux , walker circulation , atmospheric sciences , environmental science , energy balance , global warming , flux (metallurgy) , climatology , mechanics , physics , geology , climate change , materials science , sea surface temperature , thermodynamics , oceanography , metallurgy
Previous work has established that warming is associated with an increase in dry static stability, a weakening of the tropical circulation, and a decrease in the convective mass flux. Using a set of idealized simulations with specified surface warming and superparameterized convection, we find support for these previous conclusions. We use an energy and mass balance framework to develop a simple diagnostic that links the fractional area covered by the region of upward motion to the strength of the mean circulation. We demonstrate that the diagnostic works well for our idealized simulations and use it to understand how changes in tropical ascent area and the strength of the mean circulation relate to changes in heating in the ascending and descending regions. We show that the decrease in the strength of the mean circulation can be explained by the relatively slow rate at which atmospheric radiative cooling intensifies with warming. In our simulations, decreases in tropical ascent area are balanced by increases in nonradiative heating in convective regions. Consistent with previous work, we find a warming‐induced decrease in the mean convective mass flux. However, when we condition by the sign of the mean vertical motion, the warming‐induced changes in the convective mass flux are nonmonotonic and opposite between the ascending and descending regions.