Southern Hemisphere sensitivity to horizontal resolution: A simulation using a meridional stretched grid scheme

MENÉNDEZ C. G., A. F. CARRIL AND L. X. Z. LI

WMO/TD

WMO

Lugar: Ginebra, Suiza; Año: 1999 vol. 942 p. 324 - 325

The impact of horizontal resolution on the simulation of the Southern Hemisphere (SH)subtropical and polar jets is analysed. This double jet structure is one of the most peculiar features of the wintertimeSH circulation. The subtropical jet (STJ) is located at 30°S and the polar jet at about 60°S.The grid-point atmospheric global model used in this study (LMD-Z, version 1) is derived from the LMD standardAGCM (Sadourny and Laval 1984). Its horizontal discretization is a function of latitude and longitude, so astretched grid (zoom) can be applied to any region of the globe. A detailed model description is presented in Carril(1998). This model is currently running on workstations at CIMA. Since practical considerations related to thecomputational cost limit its resolution, a stretched grid with a smoothly varying mesh size has been defined. Thisgrid improves the meridional resolution in a latitudinal band in the middle southern latitudes. In order to study thesensitivity to the horizontal resolution three simulations were performed: low (64x33), medium (96x49) and high(144x73) resolution -hereafter ZL, ZM and ZH respectively-, all of them with zoom centred at 45°S and 11 verticallayers. Sea surface temperatures were fixed climatological (1979-1995) and all simulations have been run for 10years.