Twentieth century simulation of the southern hemisphere climate in coupled models. Part 1: large scale circulation variability |
| |
| Authors: | Marilyn N Raphael Marika M Holland |
| |
| Institution: | (1) UCLA Department of Geography, 1255 Bunche Hall, Los Angeles, CA 90095, USA;(2) National Center for Atmospheric Research, PO Box 3000, Boulder, CO 80307, USA |
| |
| Abstract: | The ability of five, global coupled climate models to simulate important atmospheric circulation characteristics in the Southern
Hemisphere for the period 1960–1999 is assessed. The circulation features examined are the Southern Hemisphere annular mode
(SAM), the semi-annual oscillation (SAO) and the quasi-stationary zonal wave 3 (ZW3). The models assessed are the National
Center for Atmospheric Research Community Climate System Model Version 3 (CCSM3), the Commonwealth Scientific and Industrial
Research Organisation Mark 3, the Geophysical Fluid Dynamics Laboratory Model, the Goddard Institute for Space Studies Model
ER (GISS-ER) and the UK Meteorological Office Hadley Center Coupled Model Version 3. The simulations were compared to the
NCAR–NCEP reanalyses. The models simulate a SAO which differs spatially from the observed over the Pacific and Indian oceans.
The amplitudes are too high over the southern ocean and too low over the midlatitudes. These differences are attributed to
a circumpolar trough which is too deep and extends too far north, and to the inability of the models to simulate the middle
to high latitude temperature gradient. The SAM is well-represented spatially by most models but there are important differences
which may influence the flow over the Pacific and in the region extending from the Ross to Weddell Seas. The observed trend
towards positive polarity in the SAM is apparent in the ensemble averages of the GISS-ER and CCSM3 simulations, suggesting
that the trend is due to external forcing by changes in the concentration of ozone and greenhouse gases. ZW3 is well-represented
by the models but the observed trend towards positive phases of ZW3 is not apparent in the simulations suggesting that the
observed trend may be due to natural variability, not external forcing. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
