Symmetric Instability Evaluation in Some Cases of Cloud Bands in Argentina.

SCHWARZKOPF, MARIA LUISA; ROSSO, LUIS C; MULLER, GABRIELA V.

Saint Auban, Francia.

Congreso; XXV OSTIV Congress of the International Scientific and Technical.; 1997

Organization for Liding.

Insted of a unique frontal band, parallel cloud bands of great extension, oriented approximately along the thermal wind, are frequently observed over a baroclinic zone associated to frontogenetical processes over northern Patagonia. Very often the first bands show deep convection leaving a strong aligned arrangement of thunderstorms cells. The main objective of this work was to elucidate if the corresponding conditions could be detected on cross sections constructed across the baroclinic zone, in which the vertical distribution of thermodynamic variables available from conventional radiosonda data were displayed. Based on satellite images five cases were selected, arranged from strong to weak bandedness and analyzed. The authors concluded that it is possible to visualize on an operational vertical cross section favorable conditions for slant convection and they suggest that a) the preexistent conditions of symmetric instability over northern Patagonia due to the existence of a relatively strong and narrow baroclinic zone and b) the north-south tongue distribution of the humidity over the argentine pampas with its axes to the east of 60°W, are the basic atmospheric conditions which explain tentatively the frequent fact that thunderstorms are strongly arranged on very straight lines.