| Title: |
Resolution Dependence of Tropical Poleward Energy Transport in Aquaplanet GCMs. |
| Authors: |
Chang, Chiung‐Yin1,2 (AUTHOR) cychang@princeton.edu; Lin, Pu1,3,4 (AUTHOR); Held, Isaac M.1 (AUTHOR); Merlis, Timothy M.1 (AUTHOR); Zurita‐Gotor, Pablo5,6 (AUTHOR) |
| Source: |
Journal of Advances in Modeling Earth Systems. Dec2025, Vol. 17 Issue 12, p1-20. 20p. |
| Subject Terms: |
*Atmospheric circulation; Atmospheric physics; Convective flow; Energy transfer; Atmospheric models; Latent heat |
| Abstract: |
The tropical atmosphere plays an important role in transporting energy poleward and driving the global circulation. However, understanding and simulating this fundamental aspect of our climate remains difficult due to its sensitivity to convective parameterizations and horizontal resolution. This study focuses on benchmarking the resolution dependence of tropical poleward energy transport in two aquaplanet atmospheric general circulation models with disabled convective parameterizations: a nonhydrostatic high‐resolution (100–6 km) finite‐volume cubed‐sphere model with a full physics package and a lower‐resolution (300–100 km) hydrostatic spectral model with idealized moist physics. Despite differences in their physics and numerics, both models demonstrate that column‐integrated poleward moist static energy transport by the mean meridional circulation increases with resolution in the deep tropics, while transport by transient eddies decreases. These changes are associated with enhanced gross moist stability that switches from negative to positive due to an increasingly top‐heavy mean circulation and reduced eddy activity diffusing water vapor along an unchanging mean moisture gradient. Further analysis rules out extratropical baroclinic eddies and radiation as the main drivers of these changes. Instead, the resolution dependence of both the mean meridional circulation and transient eddies appears to reflect the resolution dependence of tropical explicit (unparameterized) deep convection. We speculate the multiscale interactions of convection allow for a coupling between gross moist stability and eddy moisture flux, leading to their concurrent changes with resolution. We discuss the implications of this resolution dependence for developing theories and models of the tropical atmosphere. Plain Language Summary: The atmosphere transports energy from the tropics to the poles, helping to set the pole‐to‐equator temperature gradient. But the atmospheric circulations that are responsible for this transport differ markedly between the tropics and middle latitudes. In middle latitudes, the transport is associated with horizontal temperature contrasts between poleward and equatorward moving air in "eddies," while in the tropics the transport is due to an overturning circulation in latitude and height, the "Hadley cell," with the more energetic air moving polewards in the upper atmosphere and the less energetic air moving equatorwards near the ground. It is not fully understood why the energy transport by eddies is so small in the tropics. In this paper we study two idealized numerical atmospheric models, varying the horizontal grid size in the models, and find that the energy transport by the Hadley cell decreases with increasing grid size while the transport by eddies increases so as to keep the total transport nearly constant. This result is important for comparing models with different grid sizes that are used for climate projection and weather prediction and raises questions concerning our basic understanding of energy transport in the tropical atmosphere. Key Points: Two aquaplanet general circulation models with explicit convection have consistent changes in tropical poleward energy transport with horizontal resolutionWith increased resolution, the Hadley circulation energy transport increases, and the transient eddy energy transport decreasesThe resolution dependence seems to be controlled by convection, with gross moist stability and eddy moisture diffusivity playing key roles [ABSTRACT FROM AUTHOR] |
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| Database: |
GreenFILE |