Acceleration of Tropical Cyclone Development by Cloud-Radiative Feedbacks

Abstract

Abstract A complete understanding of the development of tropical cyclones (TC) remains elusive and forecasting TC intensification remains challenging. This motivates further research into the physical processes that govern TC development. One process that has, until recently, been under-investigated is the role of radiation. Here, the importance of radiative feedbacks in TC development and the mechanisms underlying their influence is investigated in a set of idealized convection-permitting simulations. A TC is allowed to form after initialization from a mesoscale warm, saturated bubble on an f plane, in an otherwise quiescent and moist neutral environment. Tropical storm formation is delayed by a factor of 2 or 3 when radiative feedbacks are removed by prescribing a fixed cooling profile or spatially homogenizing the model-calculated cooling profiles. The TC’s intensification rate is also greater when longwave radiative feedbacks are stronger. Radiative feedbacks in the context of a TC arise from interactions between spatially and temporally varying radiative heating and cooling (driven by the dependence of radiative heating and cooling rate on clouds and water vapor) and the developing TC (the circulation of which shapes the structure of clouds and water vapor). Further analysis and additional mechanism denial experiments pinpoint the longwave radiative feedback contributed by ice clouds as the strongest influence. Improving the representation of cloud-radiative feedbacks in forecast models, therefore, has the potential to yield critical advancements in TC prediction. Significance Statement Our understanding of the development of tropical cyclones, hurricanes, and typhoons is incomplete, and, thus, forecasting tropical cyclone formation and intensification remains challenging. This study investigates the importance of interactions between clouds and solar and infrared radiation for tropical cyclone development. I find that in idealized convection-permitting simulations, tropical cyclone development is accelerated by a factor of 2 or more with the inclusion of these cloud–radiation feedbacks. The interaction of ice clouds associated with strong thunderstorms with infrared radiation has the biggest effect. These results indicate that improving the representation of ice clouds and their radiative feedbacks in forecast models has the potential to yield critical advancements in tropical cyclone prediction.