More rain falls over tropical islands than nearby ocean areas. This enhancement of island rainfall occurs for multiple reasons, including triggering of thunderstorms by daytime heating of islands and associated sea breezes, as well as by winds blowing over mountainous islands. Although island rainfall may seem like a local subject of study, an improved understanding of it has several benefits that cut across study of global weather and climate. For example, rainfall over the large islands of the western Tropical Pacific (such as Borneo, Papua New Guinea, and Sumatra) influences wind patterns along the equatorial Pacific basin at both weather (a few weeks) and climate (seasonal) time scales. Also, a deeper understanding of tall thunderstorms in the tropics remains a major obstacle to better weather forecasts and reducing uncertainty in climate change projections. Connected with this, studying island rainfall may help address questions about whether it tends to rain more over wet or dry soils and why; these questions are important for understanding the persistence of floods and droughts. Finally, understanding how island rainfall depends on the temperature of the nearby ocean remains a challenge. This temperature-dependence is important not only for the societal impacts of rainfall extremes in a changing climate, but also because dissolved minerals found in the runoff from all land - but particularly tropical islands - can regulate atmospheric carbon dioxide content and global temperature over periods of millions of years. The goal of this project is to address these questions that cut across weather, current climate, and past climate, by using high-resolution numerical model simulations of the atmosphere to investigate how island rainfall enhancement depends on multiple factors of the island environment. These factors include the temperature of the nearby ocean, the wetness and height of the island, the strength of the winds impinging on the island, and the size of the region simulated in the numerical model.
This research project will advance knowledge about the tropical convection processes that regulate the climate, by studying how tropical convections are influenced by local aspects of the island environment. The research project supports a graduate student who will gain training in climate dynamics and preparation for a career in teaching and research in academia or commercial weather prediction, thus sustaining the pool of human resources required for excellence in climate research. Publicly available instructional videos will be produced to illustrate central concepts associated with island thunderstorms and rainfall, including sea-breezes and the pattern of thunderstorm triggering over the day. A set of tools for analyzing the output generated by the high-resolution numerical model of the atmosphere will be made available to undergraduate students, graduate students, and postdoctoral researchers.
