Wavelet Analysis of Winter Rainfall Variability over Victoria
Bilal Ahmed Usmani
Department of Bio Medial Engineering, NED University of Engineering and Technology, Karachi, Pakistan.
Saqib-Ur-Rehman . *
Department of Mathematics, University of Karachi, Karachi, Pakistan.
Abdul Jamil Khan
Mathematical Sciences Research Center, Federal Urdu University of Arts, Sciences and Technology, Karachi, Pakistan.
Kamran Khan
Mathematical Sciences Research Center, Federal Urdu University of Arts, Sciences and Technology, Karachi, Pakistan.
Syed Adnan Hussain
Department of Mathematics, University of Karachi, Karachi, Pakistan.
Syeda Sadia Zia
Department of Mathematics, University of Karachi, Karachi, Pakistan.
Tanveer Ahmed Siddiqui
Department of Mathematics, University of Karachi, Karachi, Pakistan.
Syed Inayat Ullah
Department of Mathematics, University of Karachi, Karachi, Pakistan.
*Author to whom correspondence should be addressed.
Abstract
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.
Keywords: Periodicity, Indian Ocean subtropical high pressure, atmospheric circulations, moisture and variability, wavelet analysis