Mean-flow transient perturbations interaction in the Southern Extratropics using a low-resolution GCM

CARRIL A. F. AND C. G. MENENDEZ

WMO/TD

WMO

Lugar: Ginebra, Suiza; Año: 1999 vol. 942 p. 713 - 714

The Southern Hemisphere (SH) extratropical circulation is strongly dominated by highfrequency transient perturbations. The capability of a low-resolution atmospheric global model to representthe high frequency transients and their interaction with the mean flow is investigated. This model is a versionof the LMD general circulation model installed at CIMA (LMDZ/CIMA, Carril 1998). Its horizontaldiscretization is a function of latitude and longitude, so a stretched grid or zoom can be applied to any regionof the globe. The horizontal resolution corresponds to a grid of 64 points in longitude and 33 points inlatitude. In order to enhance model resolution in the southern midlatitudes we adopt a meridional zoomcentred at 45°S (Menéndez et al. 1997). The vertical discretization is over 11 vertical layers. Sea surfacetemperature and sea ice distributions were fixed as climatological (1979-1995) and the simulation has beenrunning for ten years. Only the winter season (JJA) is analysed here.