Thermodynamic control of tropical cyclogenesis in environments of radiative‐convective equilibrium with shear

Rappin, Eric D.; Nolan, David S.; Emanuel, Kerry

doi:10.1002/qj.706

Cited by 73 publications

(92 citation statements)

References 43 publications

(38 reference statements)

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“…Figure 2 illustrates this point, showing Atlantic results from Mei et al (2014), from a 25-kmresolution version of the HiRAM, demonstrating the performance of this higher-resolution version of (2010) give decreases in the Northern Hemisphere ranging from roughly 0% to 30% and in the Southern Hemisphere from 10% to 40%. Previous explanations of this result have focused on changes in tropical stability and the associated reduction in climatological upward vertical velocity (Sugi et al 2002(Sugi et al , 2012 Oouchi et al 2006; Held and Zhao 2011) and on increased midlevel saturation deficits (drying) (e.g., Rappin et al 2010). In this argument, the tropical cyclone frequency reduction is associated with a decrease in the convective mass flux and an overall related decrease in tropical cyclone numbers.…”

Section: Tropical Cyclone Formationmentioning

confidence: 98%

Hurricanes and Climate: The U.S. CLIVAR Working Group on Hurricanes

Walsh

Camargo

Vecchi

et al. 2015

Bulletin of the American Meteorological Society

181

172

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Although a theory of the climatology of tropical cyclone formation remains elusive, high-resolution climate models can now simulate many aspects of tropical cyclone climate. T he effect of climate change on tropical cyclones has been a controversial scientific issue for a number of years. Advances in our theoretical understanding of the relationship between climate and tropical cyclones have been made, enabling us to understand better the links between the mean climate and the potential intensity (PI; the theoretical maximum intensity of a tropical cyclone for a given climate condition) of tropical cyclones. Improvements in the capabilities of climate models, the main tool used to predict future climate, have enabled them to achieve a considerably improved and more credible simulation of the present-day climatology of tropical cyclones. Finally, the increasing ability of such models to predict the interannual variability of tropical cyclone formation in various regions of the globe indicates that they are capturing some of the essential physical relationships governing the links between climate and tropical cyclones. HURRICANES AND CLIMATEPrevious climate model simulations, however, have suggested some ambiguity in projections of future numbers of tropical cyclones in a warmer world. While many models have projected fewer tropical cyclones globally (Sugi et al. 2002;Bengtsson et al. 2007b; Gualdi et al. 2008; Knutson et al. 2010), other climate models and related downscaling methods have suggested some increase in future numbers (e.g., Broccoli and Manabe 1990;Haarsma et al. 1993; Emanuel 2013a). When future projections for individual basins are made, the issue becomes more serious: for example, for the Atlantic basin there appears to be little consensus on the future number of tropical cyclones or on the relative importance of forcing factors such as aerosols or increases in carbon dioxide (CO 2 ) concentration. One reason could be statistical: annual numbers of tropical cyclones in the Atlantic are relatively small, making the identification of such storms sensitive to the detection method used.Further, there is substantial spread in projected responses of regional tropical cyclone (TC) frequency and intensity over the twenty-first century from downscaling studies (Knutson et al. 2007; Emanuel 2013a). Interpreting the sources of those differences is complicated by different projections of large-scale climate and by differences in the present-day reference period and sea surface temperature (SST) datasets used. A natural question is whether the diversity in responses to projected twenty-firstcentury climate of each of the studies is primarily | a reflection of uncertainty arising from different large-scale forcing (as has been suggested by, e.g., Villarini et al. 2011;Villarini and Vecchi 2012;Knutson et al. 2013) or whether this spread reflects principally different inherent sensitivities across the various downscaling techniques, even including different sensitivity of responses within the same model due to...

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Section: Tropical Cyclone Formationmentioning

confidence: 98%

Hurricanes and Climate: The U.S. CLIVAR Working Group on Hurricanes

Walsh

Camargo

Vecchi

et al. 2015

Bulletin of the American Meteorological Society

181

172

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“…process [Rappin et al, 2010]. Here we consider the relationship between each of these variables separately and in combination with the climatology of tracks in LGM and 20C presented in the last section.…”

Section: Journal Of Advances In Modeling Earth Systems 101002/2016msmentioning

confidence: 99%

“…Journal of Advances in Modeling Earth Systems 10.1002/2016MS000685 [Rappin et al, 2010;Emanuel, 2010, 2012]. Nolan and Rappin [2008] highlighted the complex role that even small values of vertical wind shear can exert in a changing climate: in the absence of any shear, the saturation of mid-troposphere can be reached quickly by increased surface fluxes in a warmer climate, but in the presence of even weak shear, the tendency to form more storms reversed with warming.…”

Section: Wind Shearmentioning

confidence: 99%

“…These projections are obtained using high-resolution global climate models [e.g., Murakami et al, 2012;Zhao and Held, 2012], high-resolution idealized experiments [Rappin et al, 2010;Merlis et al, 2016], as well as using dynamical downscaling using regional climate models [Knutson et al, 2008;Bender et al, 2010]. For instance, Knutson et al [2015] considered storms produced by a global model, but then used a higher-resolution model in order to simulate the most intense storms.…”

Section: Introductionmentioning

confidence: 99%

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Dynamical downscaling of tropical cyclones from CCSM4 simulations of the Last Glacial Maximum

Yoo

Galewsky

Camargo

et al. 2016

J Adv Model Earth Syst

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Dynamical downscaling of simulations of the Last Glacial Maximum (LGM) and late twentieth century (20C) were conducted using the Weather Research and Forecasting (WRF) model with the aim of (1) understanding how the downscaled kinematic and thermodynamic variables influence simulated tropical cyclone (TC) activity over the western North Pacific during the LGM and the 20C periods and (2) to test the relevance of TC genesis factors for the colder LGM climate. The results show that, despite the lower temperatures during the LGM, the downscaled TC climatology over the western North Pacific in the LGM simulation does not differ significantly from that in the 20C simulation. Among the TC environmental factors, the TC potential intensity, mid‐tropospheric entropy deficit, and vertical wind shear during the LGM were consistent with previous analyses of TC genesis factors in LGM global climate model simulations. Changes in TC genesis density between the LGM and the 20C simulations seem to be well represented by the ventilation index, a nondimensional measure of the combined effects of vertical wind shear, and thermodynamic properties, suggesting the potential applicability of those factors for TC activity evaluation during the LGM and possibly other climates.

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“…Unlike M06s simulations where surface winds gradually increased to tropical cyclone strength, N07s simulations showed a strengthening of the mid-level circulation followed by the sudden formation of an intense small scale vortex with strongest winds at the surface. Another open issue concerns the thermodynamic nature of tropical cyclogenesis (Rappin et al, 2010;.…”

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confidence: 99%

An examination of two pathways to tropical cyclogenesis occurring in idealized simulations with a cloud-resolving numerical model

Nicholls

Montgomery

2013

Atmos. Chem. Phys.

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Simulations are conducted with a cloud-resolving numerical model to examine the transformation of a weak incipient mid-level cyclonic vortex into a tropical cyclone. Results demonstrate that two distinct pathways are possible and that development along a particular pathway is sensitive to model physics and initial conditions. One pathway involves a steady increase of the surface winds to tropical cyclone strength as the radius of maximum winds gradually decreases. A notable feature of this evolution is the creation of small-scale lower tropospheric cyclonic vorticity anomalies by deep convective towers and subsequent merger and convergence by the low-level secondary circulation. The second pathway also begins with a strengthening low-level circulation, but eventually a significantly stronger mid-level circulation develops. Cyclogenesis occurs subsequently when a small-scale surface concentrated vortex forms abruptly near the center of the larger-scale circulation. The small-scale vortex is warm core throughout the troposphere and results in a fall in local surface pressure of a few millibars. It usually develops rapidly, undergoing a modest growth to form a small tropical cyclone. Many of the simulated systems approach or reach tropical cyclone strength prior to development of a prominent mid-level vortex so that the subsequent formation of a strong small-scale surface concentrated vortex in these cases could be considered intensification rather than genesis.

Experiments are performed to investigate the dependence on the inclusion of the ice phase, radiation, the size and strength of the incipient mid-level vortex, the amount of moisture present in the initial vortex, and the sea surface temperature. Notably, as the sea surface temperature is raised, the likelihood of development along the second pathway is increased. This appears to be related to an increased production of ice. The sensitivity of the pathway taken to model physics and initial conditions revealed by these experiments raise the possibility that the solution to this initial value problem is near a bifurcation point. Future improvements to model parameterizations and more accurate observations of the transformation of disturbances to tropical cyclones should clarify the conditions that favor a particular pathway when starting from a mid-level vortex

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Thermodynamic control of tropical cyclogenesis in environments of radiative‐convective equilibrium with shear

Cited by 73 publications

References 43 publications

Hurricanes and Climate: The U.S. CLIVAR Working Group on Hurricanes

Hurricanes and Climate: The U.S. CLIVAR Working Group on Hurricanes

Dynamical downscaling of tropical cyclones from CCSM4 simulations of the Last Glacial Maximum

An examination of two pathways to tropical cyclogenesis occurring in idealized simulations with a cloud-resolving numerical model

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