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Analysis of Amazon Humidity Transport to South East of Brazil During the Southern Summer (DJF)
* 1 , * 1 , * 2 , * 1
1  National Institute of Space Research
2  Institute of Aeronautics and Space


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 20oS and longitude between 315 and 305oW). This transport originates from the entrance of moisture from the North Atlantic Ocean, moving to inside of the Amazon (10oS and 3oN, and longitude between 290o and 310oW), 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.

Keywords: Climate Moisture Transport Climate Change
Comments on this paper
Specific Commets
Dear Authors:

Thank you very much for your contribution to the Conference. This topic is pretty relevant and important. I have the following specific comments/questions on the full-text:

1) ENSO. Please clarify what phase of ENSO are you referring to in any case: El Niño or La Niña.

2) Figure 1. Please provide units and size reference for arrows.

3) Two major droughts occurred in 2005 and 2010 in Amazonia. Rainfall was reduced in Sao Paulo in 2005 but no so in 2010. Could you please elaborate on the physical mechanisms that prevented the reduction in 2010?

4) Figures 2 and 3. Explain what the red and dashed lines represent.

5) Also in Figures 2 and 3. ENSO (El Niño) events cover two calendar years, and therefore are denoted in pairs [Year 0 and Year (+1)]. The red bars and analysis should be focused on the DJM of Year (+1).

6) Units. The Abstract refers to kg/kg whereas the text refers to kg/s. I suggest being consistent throughout the paper.

7) The paper by Poveda et al (2014; Seasonal precipitation patterns along pathways of South American
low-level jets and aerial rivers, Water Resour. Res., 50, 98–118) shows strong observational evidence that rainfall distribution over the pathways of South American aerial rivers is also influenced by land cover type. Could you please comment on that?

Ana Durán-Quesada
Evaluation of the method
This a problem that has been around for a long time without a formal solution, hope your work directs to one. I would recommend the analysis to be considered from the perspective of conditions in both areas, the source and the receptor so that main mechanisms driving the transport can be identified beyond whether the source is active or not. A clustering technique may be helpful for you to separate for example extremely dry conditions and enhanced SPCZ activity, this will make the relationship of the transport more transparent for analysis.