Measuring and monitoring the mesoclimate of tropical locations. Field observations from the South American altiplano during the SALLJEX

Most regions of the tropics are poorly sampled by conventional meteorological measurements. Thus, direct inferences of the mesoscale climatology of many tropical locations is difficult, especially those in mountainous areas. Similarly, explaining the atmospheric dynamics associated with the observed mesoclimatology is likewise not simple. One such region with a poorly understood mesoclimatology is the altiplano region of South America. This region includes two very large features that affect the mesoclimatology of the region; Lake Titicaca (~140km long) and a similarly large dry “lake” or salt flat, the Salar de Uyuni.

An enhanced upper-air network, involving mostly pilot balloon stations, was established over the altiplano of Peru and Bolivia as part of the South American Low Level Jet Experiment (SALLJEX) held during the rainy season of 2002-2003. In addition, a network of about 200 simple raingauges was installed across the Peruvian Altiplano. The motivation for these activities was to investigate the relationship between rainfall, synoptic-scale circulations and local topographic effects. The region is characterized by complex terrain, and the rainfall shows large spatial gradients and a strong diurnal cycle.

This talk will describe the observing networks and the analysis of the raingauge and pilot balloon data. The structure and importance of the Lake Titicaca and Salar de Uyuni breezes in modulating the rainfall will be described from both observations and from simulations using the WRF model. Implications for developing observing networks to diagnose the mesoscale climate in poorly sampled regions of the tropics (and extratropics) will be described.