Quantifying the Annular Mode Dynamics in an Idealized AtmosphereSource: Journal of the Atmospheric Sciences:;2019:;volume 076:;issue 004::page 1107DOI: 10.1175/JAS-D-18-0268.1Publisher: American Meteorological Society
Abstract: AbstractThe linear response function (LRF) of an idealized GCM, the dry dynamical core with Held?Suarez physics, is used to accurately compute how eddy momentum and heat fluxes change in response to the zonal wind and temperature anomalies of the annular mode at the quasi-steady limit. Using these results and knowing the parameterizations of surface friction and thermal radiation in Held?Suarez physics, the contribution of each physical process (meridional and vertical eddy fluxes, surface friction, thermal radiation, and meridional advection) to the annular mode dynamics is quantified. Examining the quasigeostrophic potential vorticity balance, it is shown that the eddy feedback is positive and increases the persistence of the annular mode by a factor of more than 2. Furthermore, how eddy fluxes change in response to only the barotropic component of the annular mode, that is, vertically averaged zonal wind (and no temperature) anomaly, is also calculated similarly. The response of eddy fluxes to the barotropic-only component of the annular mode is found to be drastically different from the response to the full (i.e., barotropic + baroclinic) annular mode anomaly. In the former, the eddy generation is significantly suppressed, leading to a negative eddy feedback that decreases the persistence of the annular mode by nearly a factor of 3. These results suggest that the baroclinic component of the annular mode anomaly, that is, the increased low-level baroclinicity, is essential for the persistence of the annular mode, consistent with the baroclinic mechanism but not the barotropic mechanism proposed in the previous studies.
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contributor author | Hassanzadeh, Pedram | |
contributor author | Kuang, Zhiming | |
date accessioned | 2019-10-05T06:51:25Z | |
date available | 2019-10-05T06:51:25Z | |
date copyright | 2/21/2019 12:00:00 AM | |
date issued | 2019 | |
identifier other | JAS-D-18-0268.1.pdf | |
identifier uri | http://yetl.yabesh.ir/yetl1/handle/yetl/4263638 | |
description abstract | AbstractThe linear response function (LRF) of an idealized GCM, the dry dynamical core with Held?Suarez physics, is used to accurately compute how eddy momentum and heat fluxes change in response to the zonal wind and temperature anomalies of the annular mode at the quasi-steady limit. Using these results and knowing the parameterizations of surface friction and thermal radiation in Held?Suarez physics, the contribution of each physical process (meridional and vertical eddy fluxes, surface friction, thermal radiation, and meridional advection) to the annular mode dynamics is quantified. Examining the quasigeostrophic potential vorticity balance, it is shown that the eddy feedback is positive and increases the persistence of the annular mode by a factor of more than 2. Furthermore, how eddy fluxes change in response to only the barotropic component of the annular mode, that is, vertically averaged zonal wind (and no temperature) anomaly, is also calculated similarly. The response of eddy fluxes to the barotropic-only component of the annular mode is found to be drastically different from the response to the full (i.e., barotropic + baroclinic) annular mode anomaly. In the former, the eddy generation is significantly suppressed, leading to a negative eddy feedback that decreases the persistence of the annular mode by nearly a factor of 3. These results suggest that the baroclinic component of the annular mode anomaly, that is, the increased low-level baroclinicity, is essential for the persistence of the annular mode, consistent with the baroclinic mechanism but not the barotropic mechanism proposed in the previous studies. | |
publisher | American Meteorological Society | |
title | Quantifying the Annular Mode Dynamics in an Idealized Atmosphere | |
type | Journal Paper | |
journal volume | 76 | |
journal issue | 4 | |
journal title | Journal of the Atmospheric Sciences | |
identifier doi | 10.1175/JAS-D-18-0268.1 | |
journal fristpage | 1107 | |
journal lastpage | 1124 | |
tree | Journal of the Atmospheric Sciences:;2019:;volume 076:;issue 004 | |
contenttype | Fulltext |