A Deep Convection Event above the Tunuyán Valley near the Andes Mountains

A. de la Torre Departmento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina

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V. Daniel Laboratoire de Météorologie Dynamique du CNRS, Ecole Normale Superiéure, Paris, France

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R. Tailleux Laboratoire de Météorologie Dynamique du CNRS, Université Pierre et Marie Curie, Paris, France

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H. Teitelbaum Laboratoire de Météorologie Dynamique du CNRS, Ecole Normale Superiéure, Paris, France

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Abstract

Deep convection in the Tunuyán Valley region (33°–34°S, 69°–70°W) on the eastern side of the highest peaks of the Andes Mountains is sometimes associated with damaging hail. Understanding the physical mechanisms responsible for the occurrence of deep convection in that region is therefore a central part of the development of hail suppression projects. In this paper, a case of deep convection that occurred on 22 January 2001 is studied in detail through a combined analysis of radar, satellite, and radiosonde data and numerical simulations using a nonhydrostatic mesoscale atmospheric (Meso-NH) model. The time evolution and stability characteristics are first documented using the data. In order to get insight into the main causes for the deep convection event, numerical simulations of that day were performed. These results are compared with the results corresponding to conditions of 4 January 2001 when no deep convection occurred. The comparison between the 2 days strongly suggests that the deep convection event occurred because of the simultaneous presence of anabatic winds, accumulation of moist enthalpy, and the stability conditions. The present results should be helpful in designing future observational programs in the region.

Corresponding author address: A. de la Torre, Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellon I, 1428 Buenos Aires, Argentina. Email: delatorr@df.uba.ar

Abstract

Deep convection in the Tunuyán Valley region (33°–34°S, 69°–70°W) on the eastern side of the highest peaks of the Andes Mountains is sometimes associated with damaging hail. Understanding the physical mechanisms responsible for the occurrence of deep convection in that region is therefore a central part of the development of hail suppression projects. In this paper, a case of deep convection that occurred on 22 January 2001 is studied in detail through a combined analysis of radar, satellite, and radiosonde data and numerical simulations using a nonhydrostatic mesoscale atmospheric (Meso-NH) model. The time evolution and stability characteristics are first documented using the data. In order to get insight into the main causes for the deep convection event, numerical simulations of that day were performed. These results are compared with the results corresponding to conditions of 4 January 2001 when no deep convection occurred. The comparison between the 2 days strongly suggests that the deep convection event occurred because of the simultaneous presence of anabatic winds, accumulation of moist enthalpy, and the stability conditions. The present results should be helpful in designing future observational programs in the region.

Corresponding author address: A. de la Torre, Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellon I, 1428 Buenos Aires, Argentina. Email: delatorr@df.uba.ar

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