Wavelet Analysis of Winter Rainfall Variability over Victoria

This study employ Wavelet analysis to investigate the winter (May-Aug) rainfall variability with respect to the intensity of Indian Ocean Subtropical High Pressure (IOSHPS) System and its longitude, Indian Ocean Subtropical High Longitudes (IOSHLN), positions. The physical relationship among these predictors and winter rainfall were analyzed using composites of atmospheric circulation patterns. We have found inverse association between IOSH indices and winter rainfall. We have observed that maximum rainfall variability occurred in 1-3 years periodicity during 1951-1979 when IOSHPS was located around Southern Australia. This caused moisture onshore and Victoria received more rainfall. We have also observed that highest variability from 1980-2016 with similar periodicity in IOSHPS. The shifting of IOSHPS from Southern to Southeastern Australia and increase in its intensity from the post 1979 period of the analysis era (1951-2016) cause further declined in winter rainfall over Victoria.