THE EFFECT OF THE LOW-LEVEL JET ON THE POLEWARD WATER-VAPOR TRANSPORT IN THE CENTRAL REGION OF SOUTH-AMERICA

The low-level jet (LLJ)in the central region of South America is studied. This LLJ is generated by the daily cycle of convergence and divergence east of the Andes Mountains. We use the 1973-1974 radiosonde and pilot balloon data set from the upper air weather stations, Salta and Resistencia, in northern Argentina to select 10 LLJ cases and another 10 NoLLJ cases (when the LLJ is not present). We use the University of Utah Mesoscale Model to simulate these situations in order to obtain a high-resolution low-level wind field. These model predictions are then used to calculate the meridional water vapour transport across a vertical cross-section, along 26-degrees-S in central South America. The results reveal that the LLJs are a very effective mechanism for the poleward water vapour transport.