Response of Tropical Cyclone Formation and Intensification Rates to Climate Warming in Idealized Simulations. (14th October 2020)

• Record Type: Journal Article
• Authors: Ramsay, Hamish A.; Singh, Martin S.; Chavas, Daniel R.
• Is Part Of: Journal of advances in modeling earth systems. Volume 12:Number 10(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-10-14
• Subjects: tropical cyclones -- CRM -- climate -- genesis -- rapid intensification -- self‐aggregation; Geological modeling -- Periodicals; Climatology -- Periodicals; Geochemical modeling -- Periodicals; 551.5011
• DOI: 10.1029/2020MS002086
• Languages: English
• ISSNs: 1942-2466

Abstract

Abstract: There is currently no theory for the rate of tropical cyclone (TC) formation given a particular climate, so our understanding of the relationship between TC frequency and large‐scale environmental factors is largely empirical. Here, we explore the sensitivity of TC formation and intensification rates to climate warming in a series of highly idealized cloud‐permitting simulations, in which TCs form spontaneously from a base state of rest on an f ‐plane. The simulations reveal a nonmonotonic relationship between the time taken for a TC precursor disturbance (a "seed") to form and the prescribed sea surface temperature (SST), with moderately long seed emergence times at both ends of the SST range tested (292 and 304 K) and a shorter seed emergence time at the middle value of SST (298 K). Genesis potential indices (GPIs) exhibit a different response to warming: either a monotonic increase if the potential intensity and midtropospheric relative humidity are used or relatively little sensitivity if the saturation deficit is used as the humidity variable. The sensitivity of elapsed time between a TC seed disturbance and TC genesis to surface warming is, however, generally well captured by GPIs, especially those that depend on the saturation deficit. The maximum intensification rate of TCs increases strongly with warming, particularly during the second half of the intensification process. Notably, storms intensify much more rapidly with increasing temperature than is predicted by extant theory based on potential intensity, suggesting that TCs in a warmer climate may intensify even more rapidly than recent studies suggest. Plain Language Summary: Climate change is expected to exacerbate tropical cyclone (TC) hazards, such as extreme rainfall, but there is less certainty in the projections of the overall frequency of TCs as the climate continues to warm. Here, we explore how the formation and intensification of TCs respond to a warmer climate using computer simulations that capture the full evolution of a TC, from a cluster of tropical clouds to a Category 5 hurricane in a controlled environment. Our simulations reveal a complex relationship between the likelihood of TC formation and sea surface temperature that cannot be explained by a simple trend. The maximum intensification rate of TCs, on the other hand, increases strongly with warming, suggesting that rapidly intensifying storms may become more frequent in future climate and intensify faster as the world's oceans continue to warm. Key Points: Tropical cyclones (TCs) develop spontaneously in rotating radiative‐convective equilibrium, even in the absence of interactive radiation The time taken for a TC to develop from a quiescent initial state exhibits a distinctive nonmonotonic dependence on surface warming TC intensification rate increases strongly with warming, with much larger variation than that predicted by extant theory