South American monsoon indices

Four monsoon indices (the meridional wind shear index (MWSI), the zonal wind shear index (ZWSI), the 850-hPa zonal wind index (850ZWI) and the 850-hPa zonal and meridional wind index (UVI)) based on the characteristics of the wind circulation are used to identify the onset and the demise dates and the intraseasonal variability of the rainy season over the west central Brazil (WCB) region. All the four-index time series have a high correlation with the precipitation series over WCB. The UVI, MWSI and the 850ZWI represent very well the intraseasonal variability (break and active periods) of the precipitation over WCB and the 850ZWI is also useful for identifying the onset dates. Copyright (C) 2006 Royal Meteorological Society