Brazilian component of the South American low level jet east of the Andes field experiment: interaction in meso and large scale between the Amazon and La Plata River Basins

Abstract

This project is part of a broader international research agenda of the Variability of American Monsoon Systems (VAMOS) and its component Monsoon Experiment in South America (MESA), which are sponsored by the Climate Variability and Predictability (CLIVAR) Program of the World Meteorological Organization (WMO). The proposed field experiment is also relevant to the observational and scientific activities in the continental scale experiment basins of the hydrographic basins of the Global Energy and Water Cycle Experiment (GEWEX) that includes the Amazon and La Plata River basins. In the context of VAMOS and MESA, the regional experiment on South American Low Level Jet East of the Andes (SALLJ) is basically dedicated to field observations and modeling studies of moisture transport between the Amazon and La Plata basins. There are some observational evidences as well as modeling studies that how that the Low Level Jet East of the Andes (hereafter, LLJ) is responsible for most of the moisture and energy transport between these two basins. The SALLJ field experiment has regional components in each country involved (Argentina, Bolivia, Chile, Paraguay, Peru, Uruguay and United States), and some of them already have secured or are looking for funds from international institutions as well as US agencies. The current proposal is directed to obtain funding for the Brazilian component of the SALU for the implementation of the Brazilian component of the LLJ field experiment (SALLJ-Brazil), and the observational and modeling studies associated to it. The involvement of scientists from institutions São Paulo (CPTEC/INPE, USP-IAG, CTA and IPMET), with the collaboration of researchers from Alagoas, Pará, Paraná, Rio de Janeiro, Acre, Rondonia and from countries of the southeastern region of South America plus the United States, will provide an starting point in a series of detailed and high resolution surface, upper-air and remote sensing observation, and will allow to get some answers to this science question: what is the role of the LU on the moisture transport from the Amazon to the La Plata basins? More specific science questions include: 1) how is the synoptic variability of the: LLJ ?, what is the role of the synoptic forcing associated with upper-level westerly flow?, is the Chaco Low Important in the modulation of the LLJ?, what is the role of the heat source associated to latent heat release versus senible heat on the Bolivian Altiplano and in Amazônia/West Central Brazil?; 2) what is the spatial structure and time variability from diurnal to intrasasonal time scales?, what is the role of the LLJ in the intraseasonal variability of precipitation along the ZCAS?, what is the role of the LLJ in the dynamics of the Mesoscale Convective Complexes over the La Plata Basin?, what is the dependence of the diurnal cycle of in the Andean Region to the east of the Andes in relation to the LLJ?; 3) how is the interuannual variability of the LLJ?, what is the dependence of the LLJ in relation to SST anomalies in the Pacific and Atlantic?; 4) do the atmospheric models reproduce adequately the spatial and temporal structure of the LLJ at different time and space scales?, is there any difference in the representation of the LLJ in terms of the vertical and horizontals discretization of the numerical models?; 5) what is the coupling between the occurrence or not of LLJ episodes and rainfall in the Andean region, east of the Andes, and southern Brazil-northern Argentina?; 6) what satellite based techniques and monitoring describe adequately the spatial structure and temporal variability of the LLJ? The extension and upgrading of the current observational network will allow for better and more frequent surface and upper-air directed towards a better understanding of the LLJ, based on a combination of observation and monitoring of circulation and fluxes associated to the LLJ, complemented by regional and global models. (AU)