How do Tropical Cyclones Impact the Large-Scale Climate? An Exploration Using Global Climate Models
Gabriel Rios, Princeton University
Tropical cyclones (TCs) are among the most energetic phenomena in Earth’s atmosphere. The extreme winds, intense precipitation, and storm surge associated with TCs often have catastrophic societal effects by posing significant risks to life and property. Although the effects associated with TCs have been studied extensively, the impacts of TCs on the large-scale climate have not. Despite TC effects on climate not being as immediately impactful as their direct effects along their paths, their potential influence on ocean mixing, meridional heat transport, and ability to modulate the Earth’s radiative budget shows a need to improve our understanding of their upscale effects. The climatic impacts of TCs are explored in this work using a novel algorithm to suppress TC formation in global climate models, such that the climate state with suppressed TC activity can be compared to a control state and reveal differences induced by TCs. The SWISHE (suppressed wind-induced surface heat exchange) algorithm results in a 48% reduction in TC frequency and a 91% reduction in frequency of TCs that reach hurricane-strength. The reduction in TC frequency reveals that TCs increase global mean precipitation by approximately 1%, redistribute atmospheric moisture poleward and dry the tropics, and contribute to an increase in high cloud fraction in the tropics and subtropics. The reduction also reveals that globally, TCs cool by an average of 0.1 degrees Celsius but warm and deepen the oceanic mixed layer, demonstrating their potential to mix and transport oceanic heat. Future work from this exploration points to investigation of the relationship between TC activity and the overturning circulation and the role of TCs in convective aggregation, both of which have considerable implications for Earth’s radiative balance and hydrological cycle.