Aerosol Influence on Dynamic Parameters Required for Tropical Cyclone Genesis over the Tropical Southwest Pacific Ocean in Different Madden Julian Oscillation Phases

Tropical cyclones (TC) over the Southwest Pacific Ocean (SWPO) cause major disasters in Eastern Australia (EA) because of the variable track nature. Large scale dynamic variables (vertical wind shear, relative vorticity and specific humidity) required for TC genesis create distinct patterns of interseasonal variability in TC activity over this region. This study provides an additional contributor to the variability in the dynamic conditions, atmospheric aerosol properties. This study examines the relationship between aerosol properties and dynamic variables required for TC genesis in different Madden-Julian Oscillation (MJO) phases. MJO is a leading mode of interseasonal atmospheric variability in the tropical Pacific characterized by an eastward propagating, large-scale oscillation in tropical deep convection and causes cloudiness and rainfall over the Australian region. MJO phases and associated rainfall and cloudiness could potentially impact aerosol properties through atmospheric circulation patterns and anomalies. Previous research suggests aerosol properties significantly affect TC genesis through modulating thermodynamic parameters. This study uses aerosol optical depth (AOD) and the Ångström exponent (AE: qualitative indicator of aerosol particle size) from the Moderate Resolution Imaging Spectrometer (MODIS), Advanced Very High Resolution Radiometer (AVHRR), and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) for the period 1997–2016 as the independent variables and dynamic conditions from National Center for Atmospheric Research (NCAR) as the dependent variables. Granger causality is used in this study to statistically determine the causal relationship between these aerosol properties and dynamic parameters over the tropical SWPO region in each of the eight MJO phases. This study strives to find the modulating influence of the MJO on factors affecting TC genesis. Understanding these relationships can aid in the prediction of TC genesis and will be beneficial for applying proper risk management strategies in advance.