Rossby Wave Propagation Tracks in Southern Hemisphere Mean Basic Flows Associated to Generalized Frosts over Southern South America

MULLER GABRIELA V; AMBRIZZI TÉRCIO

ATMóSFERA

CENTRO CIENCIAS ATMOSFERA UNAM

Lugar: México; Año: 2009

0187-6236

Based on previous observational studies on cold extreme events over Southern South America, some recent studies suggest a possible relationship between Rossby wave propagation remotely triggered and the occurrence of frost. Using the concept of linear wave theory, this study analyzes the path followed by the planetary waves on different basic states which were composited for events in the periods of maximum and minimum occurrence of generalized frosts over the Wet Pampa, located in central-northwest Argentina during the austral winter. In order to determine the wave trajectories the ray tracking technique is used in this study. Some theoretical discussion about this technique is also presented. The analysis of the basic state, from a theoretical point of view and based on the calculation of ray tracings, corroborates that remotely excited Rossby waves is the mechanism that favors the maximum occurrence of generalized frosts. The basic state in which the waves propagate is what conditions the places where they are excited. The Rossby waves are excited in places determined by the atmosphere, propagating towards South America along the jet streams that act as wave guides, favoring the generation of generalized frosts. In summary, this paper presents an overview of the ray tracing technique and how it can be used to investigate an important synoptic event, such as frost in a specific region, and its relationship with the propagation of large scale planetary waves.