Characterizing the dominant atmospheric conditions leading to rainfall-extreme events in the south-central Andes

The south-central Andes in NW Argentina are characterized by steep topographic and climatic gradients. The atmospheric conditions leading to rainfall extreme events along the steep topographic gradient are not sufficiently understood. The focus of the study is to characterize these dominant atmospheric conditions and their spatial variability by analyzing convective available potential energy (CAPE) and dew-point temperature (T_d) for areas stretching from the high elevation central Andean Plateau to the low-elevation foreland region. We rely on ERA-Interim reanalysis data, version 2.0 of the ECMWF (European Centre for Medium-Range Weather Forecasts) and TRMM (Tropical Rainfall Measuring Mission) data. We obtained several key results: First, based on our spatiotemporal analysis rainfall distributions are controlled by spatial differences in CAPE and T_d. Second, we identify a correlation between rainfall and combination of dew-point temperature and CAPE by a multivariable regression analysis. Our results based on p values <<0.001 indicate a statistically significant relationship between a non-linear combination of dew point temperature and CAPE and 90th percentile rainfall. Third, we observe the dew-point temperature is a more important variable in the low- and intermediate-elevation areas compared to the high-elevation Puna Plateau and CAPE as a more significant variable in high-elevation Puna Plateau compared to low- and intermediate elevation areas leading to the extreme rainfall. Fourth, we find that rainfall can be predicted with higher statistical significance at the 90th percentile using the CAPE and T_d compared to lower rainfall percentiles. Our study highlights the important role of atmospheric variables on extreme rainfall events in the south-central Andes. Our correlation analysis and model does not predict individual events, but it allows identifying the general conditions leading to rainfall-extreme events in the eastern central Andes.