zum Thema: South American atmospheric features: mountain wave effects on convection and humidity variability
Zeit: Donnerstag 8. Jänner 2015, 12:00 Uhr (s.t.)
Ort: SR des Wegener Center im 1. Stock, Brandhofgasse 5
Moderation: Ass. Prof. Andrea Steiner
Herzlich willkommen!
Abstract:
The South American sub-continent (SA) relief is characterized by the presence of the Andes range, extending along 7000 km with mountain tops about 6–7 km close to the coast. This mountain range, almost aligned in North-South direction, strongly affects the behavior of the tropospheric flow at all levels and therefore meteorological events. The presence of the Atlantic and Pacific oceans is another important feature which influences the meteorology of the region. In mid-latitudes, predominant westerly winds give place to the income of moist air from the Pacific, which is blocked by the mountains. Close tothe equator, moist flow from the Atlantic enters the continent from the East reaching the Andes and turning towards the South. The region lacks of information from radiosonde data, but GPS radio occultation observations have been demonstrated to be a useful tool for the estimation of prevailing fields in the lower atmosphere atregional scale in SA. It was possible to reproduce the spatial and temporal humidity characteristics over the region. Over the semi-arid area, produced by the blocking effect of the Andes in mid-latitudes, mountain waves and severe storms with hail production are often observed at the same time. These events were analyzed, finding several differences in radar parameters between storms in the presence or absence of mountain waves. From the analysis of instability indices such as CAPE and CIN it was found that the energy provided by mountain waves was high enough to trigger deep convection over the studied area.