Energética de um Caso de Geada Generalizada na Argentina

GAN, MANOEL ALONSO; MÜLLER GABRIELA V; PICCININI SILVEIRA VIRGINIA; AMBRIZZI, TÉRCIO

Belén

Congreso; XVI Congresso Brasileiro de Meteorologia; 2010

The energetics of a wave train associated with a prolonged event of generalized frost (GF) in the extratropical region of South America is studied. This event was the most remarkable observed during the period from 1961 to 1990. It began on July 5, 1988 and caused frost (partial and generalized) during 11 consecutive days in Argentina, of which 8 were GF in the Humid Pampa region (central-eastern Argentina). The results show a wave train that propagates through the Southern Hemisphere, following the orientation of the polar jet. In the days prior to the event, this train had a deep ridge located at approximately 120°W, associated with an intense anticyclonic anomaly, and a trough downstream (west side of Andes) with a large amplitude, during the days preceding the episode. In the geopotential anomaly field, a double wave train, on subtropical latitude and the other on the mid-latitude was observed. In the kinetic energy fields, two centers of maximum energy were observed associated with the wave train over South America: one upstream of the trough and the other downstream of the ridge during the pre-frost days and the upstream of it when the GG started (July 5, 1988 ). The main source of the maximum kinetic energy associated with the trough was the convergence of the ageostrophic flow (CAF) during the pre-frost period. During the frost period, the baroclinic conversion was the main source of energy that intensified this maximum of energy. The center of maximum energy associated with the ridge had a behavior similar to the maximum of the trough during the pre-frost period. During frost days, CAF was positive and the baroclinic conversion had positively contributed only during a few days.