Royal Dutch Meteorological Institute; Ministery Of Infrastructure And The Environment

Publications, presentations and other activities
Tropical cyclone sensitivities to CO2 doubling: Roles of atmospheric resolution, synoptic variability and background climate changes
2019
by G.A. Vecchi (Princeton University), T.L. Delworth (NOAA GFDL), H. Murakami (NOAA GFDL), S.D. Underwood (NOAA GFDL), A.T. Wittenberg (NOAA GFDL)F. Zeng (NOAA GFDL)W. Zhang (University of Iowa)J. Baldwin (Princeton University)K. Bhatia (Princeton University)W. Cooke (NOAA GFDL)J. He (Princeton University)S.B. Kapnick (NOAA GFDL)T. Knutson (NOAA GFDL)G. Villarini (University of Iowa)K. van der Wiel (KNMI)

Responses of tropical cyclones (TCs) to CO2 doubling are explored using coupled global climate models (GCMs) with increasingly refined atmospheric/land horizontal grids (~200 km, ~50 km and ~25 km). The three models exhibit similar changes in background climate fields thought to regulate TC activity, such as relative sea surface temperature (SST), potential intensity, and wind shear. However, global TC frequency decreases substantially in the 50 km model, while the 25 km model shows no significant change. The ~25 km model also has a substantial and spatially-ubiquitous increase of Category 3𣯗 hurricanes. Idealized perturbation experiments are performed to understand the TC response. Each model抯 transient fully-coupled 2證O2 TC activity response is largely recovered by 搕ime-slice experiments using time-invariant SST perturbations added to each model抯 own SST climatology. The TC response to SST forcing depends on each model抯 background climatological SST biases: removing these biases leads to a global TC intensity increase in the ~ 50 km model, and a global TC frequency increase in the ~25 km model, in response to CO2-induced warming patterns and CO2 doubling. Isolated CO2 doubling leads to a significant TC frequency decrease, while isolated uniform SST warming leads to a significant global TC frequency increase; the ~25 km model has a greater tendency for frequency increase. Global TC frequency responds to both (1) changes in TC 搒eeds, which increase due to warming (more so in the ~25 km model) and decrease due to higher CO2 concentrations, and (2) less efficient development of these搒eeds into TCs, largely due to the nonlinear relation between temperature and saturation specific humidity.

Bibliographic data
Vecchi, G.A., T.L. Delworth, H. Murakami, S.D. Underwood, A.T. Wittenberg, F. Zeng, W. Zhang, J. Baldwin, K. Bhatia, W. Cooke, J. He, S.B. Kapnick, T. Knutson, G. Villarini and K. van der Wiel, Tropical cyclone sensitivities to CO2 doubling: Roles of atmospheric resolution, synoptic variability and background climate changes
Clim. Dyn., 2019, 53, 5999-6033, doi:10.1007/s00382-019-04913-y.
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