Observed and Modeled Aspects of Central-South American Low Level Jets

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The low level jets (LLJs) that occur east of Andes Mountains in Central-South America and play a major role in the inter-basin transport of water vapor from the Amazon to the La Plata river basin are not well understood or predicted. This is, in part, due to poor observational coverage locally where spatial distribution of radiosonde sites is sparse and some of them have only one launch per day. This research project attempts to fill this observational gap and seek improved understanding and prediction of these LLJs. The research work is divided into three components. The first one is to study different features of the LLJs and their interactions with large-scale anomalies during the El Nino and La Nina summers using a global telescoping model that allows local high resolution. The second component is to launch radiosondes at two sites in Bolivia and one in Paraguay for three months in the Southern Hemisphere summer of 2002-2003 to obtain information on the diurnal and spatial structure of the LLJs. The third component will be to carry out short-term numerical simulations to calibrate and validate both the model and the reanalysis against the summer field observations. Understanding of these features may improve prediction with regional and global models. Collaborations between scientists in the U. S. and South American countries have great potential to elevate the research activities there and improve the long- term observational efforts locally. This last goal, if achieved, will have immeasurable benefits to the meteorological research and operational community.