Linking atmospheric circulation patterns with hydro-geomorphic disasters in Peru

The occurrence of El Nino has been generally considered the main driver of hydro-geomorphic processes in Peru. However, the climatic characterization of hydro-geomorphic events (HGE) occurring in the absence of El Nino remains scarce. Information contained in the DesInventar disaster database suggests a widespread occurrence of HGE associated to cold-neutral sea surface temperature (SST) in the central Pacific and south tropical Atlantic. Here, we aim at characterizing synoptic patterns associated with HGE that have occurred over last 35 years related to the different El Nino types and focusing as well on the non-Nino phases. We use the ERA-Interim reanalysis climate data and implement self-organizing maps to assess the link between HGE in Peru and specific synoptic patterns. Results suggest that synoptic patterns associated with La Nina and neutral conditions play an important role in the occurrence of hydro-geomorphic disasters in Peru during the austral summer. A total of 21% of the events are associated only with the 1972-1973, 1982-1983 and 1997-1998 El Nino events and are mainly focused in the northern Pacific coast of the country (i.e., Tumbes, Piura and Lambayeque) while more than 36% of the recorded events in the database were associated with La Nina and neutral conditions between 1970 and 2013. La Nina-related events were more relevant in the Andean-Amazonian regions, whereas neutral conditions were related to more frequent HGEs in the southern regions (south of the 13.25 degrees S) along the Peruvian Pacific coast. These outcomes imply an enhanced understanding of the synoptic mechanisms leading to the occurrence of HGE and contribute to a better understanding of the triggers of HGE causing disaster no exclusively related to El Nino-like years in Peru.