Das kontinentale Luftdruck- und Niederschlagsregime Südamerikas

Abstract

The data of 196 meteorological stations of the tropics and 208 of the extratropical zones permitted one to show in more detail aspects of the continental atmospheric pressure regime. The continental thermal low migrates between 7°S, 63°W in June and 23°S, 63°W in December. A stationary thermal orographie trough runs along the foot of the Andes from about 20°S to southern Patagonia, but in June and July only to about 40°S, interrupting throughout the year the subtropical high pressure belt. Part of this trough is the stationary low pressure cell in the Argentinian Cuyo region situated between the Andes and the highlands of the Sierras de C6rdoba and San Luis. Another thermal orographie trough is found throughout the year in all the tropical pacific coastal region, ending in a shallow low pressure system over Colombia. In the Brasilian San Francisco river basin a minor regional thermal low develops. The mean monthly and yearly positions of the Intertropical Convergence cannot be defined by means of the mean sea level pressure field analysis. In the southern hemispheric tropical and subtropical South America a simple yearly pressure oscillation takes place, but in Patagonia a double one, which corresponds with the semi-annual oscillation of the southern hemisphere at middle and high latitudes. Mainly in Venezuela, the Guayanas and the north-hemispheric part of Brazil a semiannual pressure wave also exists, which corresponds with the semi-annual oscillation of the North Atlantic Subtropical High. Concerning the geographical distribution of the occurrence of the highest/ lowest me an monthly atmospheric pressure, the influence of the thermal and dynamic components on the barometric oscillations mentioned may be appreciated. Finally, the geographical distribution of the mean yearly atmospheric pressure amplitude (highest monthly mean -lowest monthly mean) looks rather similar to that of the known mean yearly temperature amplitude.