Radiative and Dynamic Controls on Atmospheric Heat Transport over Different Planetary Rotation Rates

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  • 1 Department of Atmospheric Sciences, University of Washington, Seattle, WA
  • 2 School of Oceanography and Department of Atmospheric Sciences, University of Washington, Seattle, WA
  • 3 Department of Earth and Space Sciences, University of Washington, Seattle, WA
  • 4 Polar Science Center and Applied Physics Lab, University of Washington, Seattle, WA
  • 5 Department of Atmospheric Sciences, University of Washington, Seattle, WA
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Abstract

Atmospheric heat transport is an important piece of our climate system, yet we lack a complete theory for its magnitude or changes. Atmospheric dynamics and radiation play different roles in controlling the total atmospheric heat transport (AHT) and its partitioning into components associated with eddies and mean meridional circulations. This work focuses on two specific controls: a radiative one, atmospheric radiative temperature tendencies; and a dynamic one, planetary rotation rate. We use an idealized grey radiation model to employ a novel framework to lock the radiative temperature tendency and total AHT to climatological values, even while the rotation rate is varied. This setup allows for a systematic study of the effects of radiative tendency and rotation rate on AHT. We find that rotation rate controls the latitudinal extent of the Hadley cell and the heat transport efficiency of eddies. Both rotation rate and radiative tendency influence the strength of the Hadley cell and the strength of equator-pole energy differences that are important for AHT by eddies. These two controls do not always operate independently and can reinforce or dampen each other. In addition, we examine how individual AHT components, which vary with latitude, sum to a total AHT that varies smoothly with latitude. At slow rotation rates the mean meridional circulation is most important in ensuring total AHT varies smoothly with latitude, while eddies are most important at rotation rates similar to, and faster than, the Earth’s.

Corresponding author address: Tyler Cox, University of Washington Department of Atmospheric Sciences, 3920 Okanogan Lane NE, Seattle, WA 98195. E-mail: tylersc@uw.edu

Abstract

Atmospheric heat transport is an important piece of our climate system, yet we lack a complete theory for its magnitude or changes. Atmospheric dynamics and radiation play different roles in controlling the total atmospheric heat transport (AHT) and its partitioning into components associated with eddies and mean meridional circulations. This work focuses on two specific controls: a radiative one, atmospheric radiative temperature tendencies; and a dynamic one, planetary rotation rate. We use an idealized grey radiation model to employ a novel framework to lock the radiative temperature tendency and total AHT to climatological values, even while the rotation rate is varied. This setup allows for a systematic study of the effects of radiative tendency and rotation rate on AHT. We find that rotation rate controls the latitudinal extent of the Hadley cell and the heat transport efficiency of eddies. Both rotation rate and radiative tendency influence the strength of the Hadley cell and the strength of equator-pole energy differences that are important for AHT by eddies. These two controls do not always operate independently and can reinforce or dampen each other. In addition, we examine how individual AHT components, which vary with latitude, sum to a total AHT that varies smoothly with latitude. At slow rotation rates the mean meridional circulation is most important in ensuring total AHT varies smoothly with latitude, while eddies are most important at rotation rates similar to, and faster than, the Earth’s.

Corresponding author address: Tyler Cox, University of Washington Department of Atmospheric Sciences, 3920 Okanogan Lane NE, Seattle, WA 98195. E-mail: tylersc@uw.edu
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