Effect of tropospheric temperature change on the zonal mean circulation and SH winter extratropical cyclones |
| |
Authors: | Eun-Pa Lim Ian Simmonds |
| |
Institution: | (1) Centre for Australian Weather and Climate Research, GPO Box 1289K, Melbourne, VIC, 3001, Australia;(2) School of Earth Sciences, The University of Melbourne, Parkville, VIC, 3010, Australia |
| |
Abstract: | This study aims to understand the mechanisms which cause an overall reduction of SH extratropical cyclone activity with a
slight increase in the high latitudes in a warmer climate simulated in general circulation models (GCMs) with increasing CO2. For this purpose, we conducted idealized model experiments by forcing warm temperature anomalies to the areas where climate
change models exhibit local maximum warming—the tropics in the upper troposphere and the polar regions in the lower troposphere—simultaneously
and separately. The Melbourne University atmospheric GCM (R21) coupled with prescribed SST was utilized for the experiments.
Our results demonstrate that the reduction of SH extratropical cyclone frequency and depth in the midlatitudes but the slight
increase in the high latitudes suggested in climate change models result essentially from the tropical upper tropospheric
warming. With this tropical warming, the enhanced static stability which decreases baroclinicity in the low and midlatitudes
turns out to be a major contributor to the decrease of cyclone activity equatorward of 45°S whereas the increased meridional
temperature gradient in the high latitudes seems an important mechanism for the increase of cyclone activity over 50°–60°S. |
| |
Keywords: | Climate change Extratropical cyclones Baroclinicity Static stability Meridional temperature gradient |
本文献已被 SpringerLink 等数据库收录! |
|