Rainfall dynamics in Sri Lanka: A Review of Present Variability, Trends and Responses to Climate Change

Rainfall dynamics in Sri Lanka: A Review of Present Variability, Trends and Responses to Climate Change | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Rainfall dynamics in Sri Lanka: A Review of Present Variability, Trends and Responses to Climate Change Prabashvari Galagamage, Chamoda Payagala, Gayan Pathirana, Jong-Seong Kug, and 7 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9329627/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract Sri Lanka exhibits one of the strongest rainfall gradients in the tropics due to the interaction between complex topography, seasonally reversing monsoonal circulations and large-scale air-sea coupling. Accordingly, understanding recent changes in the spatial and temporal characteristics of rainfall is crucial for food security, water resource management and reducing disaster risk. This review synthesizes current understanding of rainfall variability, long-term trends, and climate change responses in Sri Lanka, integrating recent observational analyses (1981–2023) based on the high-resolution CHIRPS satellite-gauge blended dataset, station records, and reanalysis products. Seasonal climatology, interannual variability, and trends assessed using non-parametric Mann–Kendall and Sen's slope methods reveal pronounced spatial contrasts, with the Southwest Monsoon dominating the Wet Zone through orographic enhancement and the Northeast Monsoon controlling rainfall in the Dry Zone. The Second Inter-monsoon (October–November) emerges as the most intense and variable season, contributing disproportionately to annual totals and extreme flood events. Evidence indicates a statistically significant and spatially coherent increase in Second Inter-monsoon rainfall, alongside a post-1990s rise in wet-day frequency, suggesting a shift toward more frequent and intense rainfall episodes. Synthesized findings further demonstrate that positive phases of the Indian Ocean Dipole exert the strongest large-scale control on Sri Lankan rainfall, particularly during October–November, while the El Niño–Southern Oscillation plays a secondary and seasonally dependent role. These teleconnections operate within a rapidly warming tropical Indian Ocean, which enhances atmospheric moisture availability and amplifies rainfall extremes. Collectively, the reviewed evidence indicates increasing hydro-climatic volatility, especially in the Wet Zone, heightening risks of floods and landslides, and underscoring the urgent need for improved seasonal prediction and climate-adaptive water resource management in Sri Lanka. Sri Lanka Rainfall variability Second inter-monsoon Monsoon systems Indian Ocean Dipole El Niño-Southern Oscillation Full Text Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 15 Apr, 2026 Reviewers invited by journal 14 Apr, 2026 Editor assigned by journal 12 Apr, 2026 First submitted to journal 07 Apr, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9329627","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":623299423,"identity":"31a2067f-6f59-49bc-81ee-11e77d21d74b","order_by":0,"name":"Prabashvari Galagamage","email":"","orcid":"","institution":"University of Ruhuna","correspondingAuthor":false,"prefix":"","firstName":"Prabashvari","middleName":"","lastName":"Galagamage","suffix":""},{"id":623299424,"identity":"d4c005dc-0cd3-4589-8420-96a59be3c6f0","order_by":1,"name":"Chamoda Payagala","email":"","orcid":"","institution":"University of Ruhuna","correspondingAuthor":false,"prefix":"","firstName":"Chamoda","middleName":"","lastName":"Payagala","suffix":""},{"id":623299425,"identity":"a25e16ed-1111-4327-bcbb-814d603ff5c2","order_by":2,"name":"Gayan Pathirana","email":"data:image/png;base64,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","orcid":"https://orcid.org/0000-0002-4670-579X","institution":"University of Ruhuna","correspondingAuthor":true,"prefix":"","firstName":"Gayan","middleName":"","lastName":"Pathirana","suffix":""},{"id":623299426,"identity":"1a9a4db8-9811-4e22-9f6e-a6ed68d3766c","order_by":3,"name":"Jong-Seong Kug","email":"","orcid":"","institution":"Seoul National University","correspondingAuthor":false,"prefix":"","firstName":"Jong-Seong","middleName":"","lastName":"Kug","suffix":""},{"id":623299427,"identity":"0bde532f-4a84-40bb-864e-8d0164df8412","order_by":4,"name":"K.S.S. 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