Interannual variability of summertime convective cloudiness and precipitation in the central Andes derived from ISCCP-B3 data

The interannual variability of austral summer [December–January–February–March (DJFM)] convective ac-tivity and precipitation in the central Andes (158–308S) is investigated between 1983 and 1999 based on in situ rain gauge measurements, International Satellite Cloud Climatology Project (ISCCP) reduced radiance satellite data (the B3 dataset), and National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis data. Twice-daily ISCCP-B3 calibrated infrared data, corrected for limb-darkening effects and representing equiv-alent blackbody temperatures Tb emitted by clouds are used to derive seasonal composites of fractional cold cloud coverage F*. Comparison of in situ rain gauge measurements with F * show a good correlation when a temperature threshold Tb 5 240 K is used to derive F*. A rotated empirical orthogonal function (REOF) applied to the seasonal estimates of F * yielded three spatially separated modes of convective activity in the south, northwest, and northeast of the central Andes. Results indicate that precipitation variability in the central Andes shows less spatial coherence than previously thought, with many years showing an antiphasing of wet/dry conditions between the northern and southern part of the study area. Regression analyses confirm the crucial role of both intensity and location of upper-ai