Estudo de eventos climáticos extremos na Amazônia Ocidental e seus impactos na hidrovia rio Madeira.

Abstract

This research aimed to study climate extremes in western Amazonia (Acre, Amazonas, Roraima and Rondônia) and their impact on load flow in the Madeira River waterway. Rio levels data were used, precipitation and sea surface temperature (1990-2014). And applied the standardized precipitation index to classify dry years in the region. The years 1998, 2005 and 2010 were classified as very dry years. The 1997 – 1998 and 2009 – 2010 events presented similar characteristics in the Pacific with El Niño conditions followed by a rapid transition to La Niña conditions. All three events were marked by excessively warm sea surface temperatures in the tropical North Atlantic. Particularly in 2010 sea surface temperatures reached the highest values in history in the tropical North Atlantic, contributing to the establishment of a local meridional Hadley circulation with upward vertical motion over the North Atlantic and downward vertical motion (subsidence) over the Amazon. The combination of El Niño conditions in the Pacific with warm sea surface conditions in the North Atlantic reinforce subsidence conditions in the Amazon, which are unfavourable to the occurrence of precipitation. Even though humidity existed in the tropical atmosphere, cloud formation was inhibited by subsidence. In terms of drought spatial extent over the Amazon, the year 1998 presented the largest area with abnormal precipitation deficit, followed by 2010 and 2005 when drought conditions were restricted to the southwestern Amazon. We also observed a reduction in the load flow in the waterway Madeira River in the months of July, August and September 2010.