Impact of Aerosols and Ocean Temperature on Tropical Cyclone Days Near Australia

Abstract

Tropical cyclones (TCs) devastate nations around the world. Many different variables influence TC intensification or decay. Near Australia, one of those influences may stem from the arid interior of the landmass. The influences of aerosol optical depth (AOD), sea surface temperature (SST) and upper ocean temperature (UOT) on monthly TC days over eastern Australia and the southwest Pacific Ocean are examined using data from 1985 to 2015. The area experiences TCs in November (Nov) through June with a peak in March. Variables occurring together in time are considered as possible predictors of TC days, as well as lagged relationships between them. Spearman rank correlation tests showcase the significant relationships between all pairs of variables during a variety of months. A Poisson multiple regression model is applied on TC-SST-AOD and TC-UOT-AOD to find the most significant relationships between the variables throughout the season. Four significant models are found without violating statistical assumptions. An increase in Nov AOD and Dec SST leads to a significant increase in Jan TC days. Dec UOTs are found to be negatively related to TC days in Jan. The difference in directions is related to the difference in heating mechanisms associated with the surface conditions and the lower subsurface in environments of relatively higher AOD. Probabilities of monthly days during unfavorable and favorable conditions are found. Low to moderate TC days are expected in Jan when both Nov AOD and Dec SSTs are low. There is a chance of a higher number of Jan TC days in both high Nov AOD and Dec SSTs. This study provides scenarios between the variables to aid in forecasting.