ANNUAL AND DAILY METEOROLOGICAL CYCLES AT HIGH-ALTITUDE ON A TROPICALMOUNTAIN

An automated weather station was installed in October 1996 at the summ it of Nevado Sajama, located in the western Andean Cordillera of Boliv ia (6542 m, 18 degrees 06'8, 68 degrees 53'W). Meteorological conditio ns on the mountain are being observed to improve the calibration of ge ochemical variations within tropical ice cores. This article documents the design and operation of the station and presents a discussion of measurements made through the first annual cycle. Variables analyzed i nclude pressure, incoming solar radiation, air temperature, humidity, wind, and snow accumulation. Large diurnal fluctuations were recorded in most variables, which is not unexpected given the location at 18 de grees S; the data also reveal substantial day-to-day variability and r apid seasonal changes in weather and circulation. As a result, snowfal l events and periods of evaporation are more episodic in nature than p reviously believed. Measurement of atmospheric conditions during and b etween snowfall events will therefore greatly facilitate the interpret ation of geochemical variations in each resultant snowpack layer.