Multiscale Analysis of the Summertime Precipitation over the Central Andes

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Abstract
Precipitation over the central Andes in South America exhibits a marked annual march, with most of the rainfall concentrated during the austral summer season (December–February), when the atmospheric circulation favors the uplifting of moist air from the lowlands to the east of the mountain range. Within its rainy season, the central Andes experiences week-long rainy and dry episodes. The large-scale and local conditions during these episodes are investigated using satellite imagery, reanalyzed atmospheric fields, and in situ data. Despite the deep layer of conditional instability prevalent during most summertime afternoons, deep convection can occur only on those days in which the mixing ratio within the local boundary layer exceeds some threshold (∼7 g kg−1), yielding saturation of near-surface air parcels rising more than 600 m above ground. Convective cloudiness anomalies over the central Andes extend southeastward and tend to be concurrent with anomalies of opposite sign over the eastern par... Abstract Precipitation over the central Andes in South America exhibits a marked annual march, with most of the rainfall concentrated during the austral summer season (December–February), when the atmospheric circulation favors the uplifting of moist air from the lowlands to the east of the mountain range. Within its rainy season, the central Andes experiences week-long rainy and dry episodes. The large-scale and local conditions during these episodes are investigated using satellite imagery, reanalyzed atmospheric fields, and in situ data. Despite the deep layer of conditional instability prevalent during most summertime afternoons, deep convection can occur only on those days in which the mixing ratio within the local boundary layer exceeds some threshold (∼7 g kg−1), yielding saturation of near-surface air parcels rising more than 600 m above ground. Convective cloudiness anomalies over the central Andes extend southeastward and tend to be concurrent with anomalies of opposite sign over the eastern par...

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