Large-scale dynamics of extreme precipitation in the tropical Andes: combining weather radar observations and reanalysis data

Abstract

Extreme precipitation events are a global threat to human wellbeing, they are the main cause of natural disasters such as flooding and landslides. Floods are particularly harmful because they can trigger infectious disease outbreaks, cause damage to essential infrastructure, impact food and water security, and even affect the mental health of the population. Climate change has caused an intensification of extreme precipitation events globally in the last decades, including the tropics, which receive more than half of the global precipitation. In this context, the understanding of the climate dynamics related to extreme precipitation events is vital for climate change adaptation. Such understanding has been particularly limited in the tropical Andes, primarily because of the paucity of data in the region. In the present study, we used data from a weather radar installed at 4450 m a.s.l. in the southern Ecuadorian Andes and ERA5 reanalysis to examine the large-scale dynamics associated with extreme precipitation events in the tropical Andes during the 2015–2022 period. We found that extreme rainfall in the Interandean valley is connected to local positive near surface temperature and CAPE anomalies that extend to the eastern slopes of the Andes, which cause strong thermal convection and intense afternoon events. On the other hand, extreme rainfall over the western slopes and the coastal plains is associated with El Niño-like conditions that produce Mesoscale Convective Systems that survive well after sunset and cause extreme nighttime precipitation. The present study allowed us to reveal the connections between large-scale dynamics and extreme precipitation for the first time in the southern Ecuadorian Andes. The outcome of the present study could be useful in future research to improve forecasting of extreme precipitation events and early warning systems in the region