Tropical Cyclogenesis

Tropical cyclones are a extreme weather phenomena that have significant impacts on society. However, there remain significant gaps in our understanding of tropical cyclones, particularly how they form. There is no accepted theory for what controls the number of tropical cyclones that form in a particular climate, which hampers our ability to make confident projections about how tropical cyclones might change in the future. We conduct basic research on the fundamental physical mechanisms of tropical cyclone formation ("tropical cyclogenesis"). We use a combination of tools, including idealized cloud-resolving model simulations and analysis of observations and global climate models. One hypothesis that we investigate is that the radiative-convective feedbacks responsible for self-aggregation of convection are important for tropical cyclogenesis. In particular, there is increasing evidence that tropical cyclogenesis is accelerated by cloud-radiative feedbacks, which we investigate across a hierarchy of models and in satellite observations.

The movie above shows the evolution of clouds and humidity during a cloud resolving model simulation of spontaneous tropical cyclone formation. The simulation uses a framework of rotating radiative-convective equilibrium on an f-plane at 20N. The white shading is the mixing ratio of total cloud condensate, indicating the presence and amount of clouds, and the colors indicate the water vapor mixing ratio near the surface. Each frame is an hourly snapshot and the simulation runs for 100 days. Thanks to Ryan Abernathey for helping to create the visualization! We have found that the initial spontaneous development of a broad circulation is driven by feedbacks involving longwave radiation and surface enthalpy fluxes, which is similar to self-aggregation of convection. As the tropical cyclone intensifies further, feedbacks involving the surface winds and surface enthalpy fluxes become more important. While not strictly necessary, radiative feedbacks significantly accelerate tropical cyclogenesis; a topic we continue to investigate.

Process-Oriented Diagnostics of Tropical Cyclones in Climate Models

We also are exploring tropical cylogenesis and intensification processes in historical simulations with high-resolution climate models, including both coupled and uncoupled configurations. We track the formation and evolution of tropical cyclones in the climate model simulations and apply our analysis both along the individual tracks and composited over many tropical cyclones. Our analysis framework includes diagnostics that reveal the physical processes responsible for a good simulation of tropical cyclones. These diagnostics help us identify sources of model biases and target areas for improvement. We are also developing process-oriented diagnostics for tropical disturbances, which may serve as precursors to tropical cyclones. Understanding how tropical disturbances are represented in global climate models, and whether the models correctly distinguish between those that develop into tropical cyclones and those that do not, may be essential for improving model simulation of tropical cyclone frequency.

The below movie shows an example of one of these diagnostics in six different climate models, the column-integrated moist static energy variance budget composited over the life cycle of the tropical cyclone relative to the time it reaches its lifetime maximum intensity (LMI). The first row shows the composite TC intensity throughout its life cycle, the second row shows the radiative feedback as a function of latitude and longitude relative to the center of the TC, and the third row shows the surface flux feedback as a function of latitude and longitude relative to the center of the TC.

Papers on this topic
Tropical Cyclogenesis
Wing, A.A. (2021): Acceleration of tropical cyclone development by cloud-radiative feedbacks, J. Atmos. Sci., in review.

Sobel, A.H., A.A. Wing, S.J. Camargo, C.M. Patricola, G.A. Vecchi, C.-Y. Lee, and M.K. Tippett (2021): Tropical cyclone frequency, Earth's Future, in review.

Ruppert, Jr., J.H., A.A. Wing, X. Tang, and E.L. Duran (2020): The critical role of cloud-infrared radiation feedback in tropical cyclone development, Proc. Nat. Acad. Sci., 117, 27884-27892, doi:10.1073/pnas.2013584117.
Carstens, J. and A.A. Wing, (2020): Tropical cyclogenesis from self-aggregated convection in numerical simulations of rotating radiative-convective equilibrium, J. Adv. Model. Earth Syst., 12, e2019MS002020, doi:10.1029/2019MS002020.
Wing, A.A., S.J. Camargo, and A.H. Sobel (2016), Role of radiative-convective feedbacks in spontaneous tropical cyclogenesis in idealized numerical simulations, J. Atmos. Sci., 73, 2633-2642, doi:10.1175/JAS-D-15-0380.1.
TCs in Global Models
Camargo, S.J, C.F. Giulivi, A.H. Sobel, A.A. Wing, D. Kim, Y. Moon, J.D.O. Strong, A.D. Del Genio, M. Kelley, H. Murakami, K.A. Reed, E. Scoccimarro, G.A. Vecchi, M.F. Wehner, C. Zarzycki, and M. Zhao (2020): Characteristics of model tropical cyclone climatology and the large-scale environment, J. Climate, 33, 4463–4487, doi:10.1175/JCLI-D-19-0500.1.
Wing, A.A., S.J. Camargo, A.H. Sobel, D. Kim, Y. Moon, H. Murakami, K.A. Reed, G.A. Vecchi, M.F. Wehner, C. Zarzycki, and M. Zhao (2019), Moist static energy budget analysis of tropical cyclone intensification in high-resolution climate models, J. Climate, 32, 6071–6095, doi:10.1175/JCLI-D-18-0599.1.
Maloney, E.D., A. Gettelman, Y. Ming, J.D. Neelin, D. Barrie, A. Mariotti, C.-C. Chen, D. R. B. Coleman, Y.-H. Kuo, B. Singh, H. Annamalai, A. Berg, J.F. Booth, S.J. Camargo, A. Dai, A. Gonzalez, J. Hafner, X. Jiang, X. Jing, D. Kim, A. Kumar, Y. Moon, C.M. Naud, A.H. Sobel, K. Suzuki, F. Wang, J. Wang, A.A. Wing, X. Xu, M. Zhou (2019), Process-oriented evaluation of climate and weather forecasting models, Bull. Amer. Meteorol. Soc., 100, 1665–1686, doi:10.1175/BAMS-D-18-0042.1.
Kim, D., Y. Moon, S.J. Camargo, A.A. Wing, A.H. Sobel, H. Murakami, G.A. Vecchi, M. Zhao, and E. Page (2018), Process-oriented diagnosis of tropical cyclones in high-resolution GCMs, J. Climate, 31, 1685-1702, doi:10.1175/JCLI-D-17-0269.1.
Camargo, S.J. and Wing, A.A. (2016),Tropical cyclones in climate models, WIREs Clim Change, 7, 211-237, doi: 10.1002/wcc.373.