Extreme precipitation and temperature events in the Colombian Andes during ENSO and Neutral years

Abstract

ABSTRACT : The Andes of Colombia is a region highly influenced by changes in the mean and extreme precipitation and temperature fields during El Niño–Southern Oscillation (ENSO). Here we study the influence of the ENSO phenomenon on extreme precipitation events (EPE) and extreme temperature events (ETE) and explore the atmospheric circulation patterns that contribute to the EPEs. EPEs were characterized from the 95th and 99th percentiles and ETEs through the 99th percentile for daytime and nighttime maxima (TXx ) and minima (TNn). Our results suggest that EPEs do not show differences in intensity between La Niña (LN), EN (EN), and neutral years; however, the frequency is higher during LN and the September-October-November season. Additionally, a cluster analysis was performed where five regions with similar characteristics were found for their intensity in the EPEs. This finding is consistent with the spatial patterns observed at the in situ stations. On the other hand, diurnal and nocturnal TXx and TNn were more intense during EN. While TXx are more frequent during EN, and TNn are more frequent during LN, in both nocturnal and diurnal. Transitioning our analysis to the atmospheric context, the circulation patterns exhibited favorable conditions for the onset of EPEs during LN in northern South America; in addition, the horizontal fields showed agreement between the 2010-2012 LN event and the composite, except for the vertical profile where the atmospheric conditions may be different from other LN events in some months. The moisture flux in the vertical showed that moisture sources are available during the year but may change during EN, LN, and neutral years.