Premium
General circulation driven by baroclinic forcing due to cloud layer heating: Significance of planetary rotation and polar eddy heat transport
Author(s) -
Yamamoto Masaru,
Takahashi Masaaki
Publication year - 2016
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
eISSN - 2169-9100
pISSN - 2169-9097
DOI - 10.1002/2015je004983
Subject(s) - baroclinity , atmospheric sciences , thermal wind , middle latitudes , zonal and meridional , hadley cell , geophysics , geology , wind shear , climatology , physics , meteorology , wind speed , general circulation model , oceanography , climate change
A high significance of planetary rotation and poleward eddy heat fluxes is determined for general circulation driven by baroclinic forcing due to cloud layer heating. In a high‐resolution simplified Venus general circulation model, a planetary‐scale mixed Rossby‐gravity wave with meridional winds across the poles produces strong poleward heat flux and indirect circulation. This strong poleward heat transport induces downward momentum transport of indirect cells in the regions of weak high‐latitude jets. It also reduces the meridional temperature gradient and vertical shear of the high‐latitude jets in accordance with the thermal wind relation below the cloud layer. In contrast, strong equatorial superrotation and midlatitude jets form in the cloud layer in the absence of polar indirect cells in an experiment involving Titan's rotation. Both the strong midlatitude jet and meridional temperature gradient are maintained in the situation that eddy horizontal heat fluxes are weak. The presence or absence of strong poleward eddy heat flux is one of the important factors determining the slow or fast superrotation state in the cloud layer through the downward angular momentum transport and the thermal wind relation. For fast Earth rotation, a weak global‐scale Hadley circulation of the low‐density upper atmosphere maintains equatorial superrotation and midlatitude jets above the cloud layer, whereas multiple meridional circulations suppress the zonal wind speed below the cloud layer.