Rossby wave propagation during winters of maximum frequency of frost occurrence over the wet pampa

The influence of extratropical waves on the development of extreme cold events over southeast South America, particularly on the Argentinean Wet Pampa region is studied in this work. An anomalous heating observed over the occidental tropical Pacific Ocean, northeast of Australia, during Austral winters of maximum frequency of Generalized Frost (GF) occurrence over the center-east of Argentina, known as Wet Pampa (WP), acts as a Rossby wave source which generate waves that propagate towards the South American continent favoring the frost events. The wave propagation pattern obtained from simulations using a Global Baroclinic Model shows wavenumber 3 dominance. Additional, upper and lower levels meridional wind correlations during the GF events selected were analyzed. The 250hPa global meridional wind shows a significant correlation (0.9) with the meridional wind at the WP region. The wave propagation pattern observed in this case agrees with that simulated by the model when a heating source is located at the Pacific tropical ocean. Also, significant correlation values were found for the low level southern winds at the WP region. The wave pattern simulated shows a good correlation between the hemispheric meridional wind at higher levels and the air temperature in the day of GF events.

Rossby waves; Frost; Convection; Argentinean Wet Pampa

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