Analysis of Amazon Humidity Transport to South East of Brazil During the Southern Summer (DJF)

The moisture transport from the Amazon to the Southeast (SE) of Brazil is an important atmospheric mechanism that contributes to the high precipitation rates during the austral summer (DJF) in this region, or more specifically, in the Sao Paulo state (27 and 20^oS and longitude between 315 and 305^oW). This transport originates from the entrance of moisture from the North Atlantic Ocean, moving to inside of the Amazon (10^oS and 3^oN, and longitude between 290^o and 310^oW), where it is supplied by rivers and aerial lakes, resulting of rain forest evapotranspiration. After this supply, the moisture flow is diverted to larger latitudes (South and Southeast) due to the Andes mountain range. Another important system that also assists precipitation in the SE region during the summer period is the frontal systems that are supplied by the transport of this moisture and, when they remain stationary, form a large band of cloudiness with NW / SE orientation, called the South Atlantic Convergence Zone (SACZ), which supplies, along with the frontal systems (on average 5 passes during the summer (DJF)) the SE region. This integrated vertical moisture transport (from the surface up to 500hPa) was studied for the years that occurred El Niño Southern Oscillation (ENSO) events and in neutral years. The results show an intensification of this flow in years of ENSO. In neutral years, thereabout 45.1 kg / kg enter the Amazon territory and thereabout 27.5 kg / kg of this moisture exits, and in the region of São Paulo it receives an average amount of 8.9 kg / kg and loses 7kg / kg. When the ENSO phenomenon occurs, the flow pattern increases significantly in the two regions: the input (54.8 kg / kg) and the outflow (47.4 kg / kg) in Amazon are larger, with São Paulo receiving 42, 2 kg / kg and loses 11.8 kg / kg of all moisture received. In years of ENSO, there is an intensification of the jet stream in the central part of Brazil, blocking the passage of frontal systems. The reduction of precipitation in this period in the SE region by the SACZ is compensated by the greater humidity transport from the Amazon, and therefore, not changing in the precipitation pattern.