Joint Probability of Cyclonic Wind Speed and Maximum Rainfall for Cyclones Affected Sri Lanka

Tropical cyclones pose significant risks to coastal regions, with impacts including high wind speeds, heavy rainfall, and storm surges. This study aims to analyse the joint probability of cyclonic wind speed and maximum rainfall for cyclones affecting Sri Lanka using the Copula theory. Historical data from 33 cyclones that made landfall in Sri Lanka between 1900 and 2020 were analysed. Through exploratory data analysis and marginal distribution analysis, the Generalized Pareto distribution and Pearson type III distribution were identified as the best fits for cyclonic wind speed and rainfall, respectively. The study employed the Clayton copula to model the joint distribution of these variables, given its suitability for capturing moderate correlation and tail dependence. Optimisation of the copula parameters led to a synthetic dataset that validated the copula model’s accuracy. The results revealed a moderate correlation between wind speed and rainfall. The joint return periods were calculated using the copula model, providing crucial insights into the likelihood of simultaneous occurrences of specific wind speeds and rainfall intensities. This statistical relationship offers valuable insights for coastal flood modelling and risk mitigation strategies in Sri Lanka, aiding policymakers and stakeholders in preparing for and mitigating the impacts of tropical cyclones.