On the Temporal Decay of Tropical Cyclones Over the Ocean

It is important to understand how tropical cyclones (TCs) decay over the ocean as this is a critical pre-landfall stage. A modified exponential decay model (beta model) with two parameters alpha and beta is proposed. The scale parameter alpha defines the decay scale, while the shape parameter beta determines whether the decay rate decelerates or accelerates over time. Global fittings indicate that around 40% of TCs exhibit decelerating decay ( beta <= 1), while the majority (about 60%) show accelerating decay ( beta> 1). Correlation analysis reveals a strong negative correlation between the scale parameter alpha and the initial Coriolis parameter ( r =- 0 . 96 ) and a positive correlation between the shape parameter beta and the meridional component of the initial translation velocity ( r = 0.75). The beta model provides a comprehensive understanding of how TCs decay with time and how environmental conditions affect the decay scale and evolution.