Atmospheric heat transport is governed by meridional gradients in surface evaporation in modern-day earth-like climates

Evaporation adds moisture to the atmosphere, while condensation removes it. Condensation also adds thermal energy to the atmosphere, which must be removed from the atmosphere by radiative cooling. As a result of these two processes, there is a net flow of energy driven by surface evaporation adding...

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Published in:Proceedings of the National Academy of Sciences - PNAS 2023-06, Vol.120 (25), p.e2217202120-e2217202120
Main Authors: Fajber, Robert, Donohoe, Aaron, Ragen, Sarah, Armour, Kyle C, Kushner, Paul J
Format: Article
Language:English
Subjects:
Atmosphere
Atmospheric models
Carbon dioxide
Carbon dioxide concentration
Condensation
Cooling
Equator
Evaporation
Heat transport
Moisture effects
Perturbation
Physical Sciences
Thermal energy
Winter
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Summary:Evaporation adds moisture to the atmosphere, while condensation removes it. Condensation also adds thermal energy to the atmosphere, which must be removed from the atmosphere by radiative cooling. As a result of these two processes, there is a net flow of energy driven by surface evaporation adding energy and radiative cooling removing energy from the atmosphere. Here, we calculate the implied heat transport of this process to find the atmospheric heat transport in balance with the surface evaporation. In modern-day Earth-like climates, evaporation varies strongly between the equator and the poles, while the net radiative cooling in the atmosphere is nearly meridionally uniform, and as a consequence, the heat transport governed by evaporation is similar to the total poleward heat transport of the atmosphere. This analysis is free from cancellations between moist and dry static energy transports, which greatly simplifies the interpretation of atmospheric heat transport and its relationship to the diabatic heating and cooling that governs the atmospheric heat transport. We further demonstrate, using a hierarchy of models, that much of the response of atmospheric heat transport to perturbations, including increasing CO concentrations, can be understood from the distribution of evaporation changes. These findings suggest that meridional gradients in surface evaporation govern atmospheric heat transport and its changes.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.2217202120