Characteristics of Precipitation Features and Annual Rainfall during the TRMM Era in the Central Andes

Abstract

he central Andes extends from 7° to 21°S, with its eastern boundary defined by elevation (1000 m and greater) and its western boundary by the coastline. The authors used a combination of surface observations, reanalysis, and the University of Utah Tropical Rainfall Measuring Mission (TRMM) precipitation features (PF) database to understand the characteristics of convective systems and associated rainfall in the central Andes during the TRMM era, 1998?2012. Compared to other dry (West Africa), mountainous (Himalayas), and dynamically linked (Amazon) regions in the tropics, the central Andes PF population was distinct from these other regions, with small and weak PFs dominating its cumulative distribution functions and annual rainfall totals. No more than 10% of PFs in the central Andes met any of the thresholds used to identify and define deep convection (minimum IR cloud-top temperatures, minimum 85-GHz brightness temperature, maximum height of the 40-dBZ echo). For most of the PFs, available moisture was limited (<35 mm) and instability low (<500 J kg?1). The central Andes represents a largely stable, dry to arid environment, limiting system development and organization. Hence, primarily short-duration events (<60 min) characterized by shallow convection and light to light?moderate rainfall rates (0.5?4.0 mm h?1) were found.