NWC REU 2003
May 26 - August 2



Summertime Precipitation Variability and Atmospheric Circulation over the South American Altiplano: Effects of Lake Titicaca and Salar de Uyuni

Maura Hahnenberger, Michael Douglas, and Jose Galvez



The South American Altiplano is a high altitude plateau located between 15°S and 22°S and lying between two mountain chains of the Central Andes. Within the plateau are two large features of surface discontinuity that influence local circulations. Lake Titicaca, at the north end of the Altiplano is has an area of 8,300 square km making it the 2nd largest lake in South America. The Salar de Uyuni is the largest dry salt lake in the world with a surface area of 9000 square km. These features and their influences on local circulation can possibly change weather and climate of their surrounding areas. The aim of this study is to use pilot balloon soundings and rain gauge measurements to describe the influence of these features on their surroundings, and the impact on precipitation. Large-scale results showed a relationship between upper-level easterly flow and wet days on the Altiplano, in addition to the opposite; westerly flow and dry days on the altiplano. On the local scale we observed a tendency for increased precipitation with proximity to the lake. The difference in flow on wet and dry days also modified the diurnal breeze circulation of the lake. Analysis of morning and afternoon near-surface winds at the lake and salar indicate morning confluence and afternoon difluence, which may be linked to increased morning convection over the lake indicated by satellite imagery. Comparison of the Salar and Lake indicated a stronger breeze signal at the Salar, possibly a result of the resistance of the salt surface to heating, and reduction of daytime surface heating surrounding Lake Titicaca due to increased vegetation.

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