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Climate Mechanism for Stronger Typhoons in a Warmer World
Title
Climate Mechanism for Stronger Typhoons in a Warmer World.
Creator
Kang, Nam-Young, Elsner, James B.
Abstract/Description
Violent typhoons continue to have catastrophic impacts on economies and welfare, but how they are responding to global warming has yet to be fully understood. Here, an empirical framework is used to explain physically why observations support a tight connection between increasing ocean warmth and the increasing intensity of supertyphoons in the western North Pacific. It is shown that the energy needed for deep convection is on the rise with greater heat and moisture in the lower tropical...
Show moreViolent typhoons continue to have catastrophic impacts on economies and welfare, but how they are responding to global warming has yet to be fully understood. Here, an empirical framework is used to explain physically why observations support a tight connection between increasing ocean warmth and the increasing intensity of supertyphoons in the western North Pacific. It is shown that the energy needed for deep convection is on the rise with greater heat and moisture in the lower tropical troposphere but that this energy remains untapped when air pressure is high. Accordingly, tropical cyclone formation is becoming less common, but those that do form are likely to reach extreme intensities from the discharge of stored energy. These thermodynamic changes to the environment most significantly influence the upper portion of extreme typhoon intensities, indicating that supertyphoons are likely to be stronger at the expense of overall tropical cyclone occurrences in the western North Pacific.
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Date Issued
2016-02
Identifier
FSU_libsubv1_wos_000369285500001, 10.1175/JCLI-D-15-0585.1
Format
Citation
Global Observations Of Horizontal Mixing From Argo Float And Surface Drifter Trajectories
Title
Global Observations Of Horizontal Mixing From Argo Float And Surface Drifter Trajectories.
Creator
Roach, Christopher J., Balwada, Dhruv, Speer, Kevin
Abstract/Description
Mixing by mesoscale eddies in the ocean plays a major role in setting the distribution of oceanic tracers, with important implications for physical and biochemical systems at local to global scales. Roach et al. (2016; https://doi.org/10.1002/2015JC011440) demonstrated that a two-particle analysis of Argo trajectories produces robust estimates of horizontal mixing in the Southern Ocean. Here we extend this analysis to produce global 1 degrees x1 degrees maps of eddy diffusivity at the nominal...
Show moreMixing by mesoscale eddies in the ocean plays a major role in setting the distribution of oceanic tracers, with important implications for physical and biochemical systems at local to global scales. Roach et al. (2016; https://doi.org/10.1002/2015JC011440) demonstrated that a two-particle analysis of Argo trajectories produces robust estimates of horizontal mixing in the Southern Ocean. Here we extend this analysis to produce global 1 degrees x1 degrees maps of eddy diffusivity at the nominal Argo parking depth of 1,000 m. We also applied this methodology to estimate surface eddy diffusivities from Global Drifter Program (GDP) surface drifters. The global mean eddy diffusivity was 543 +/- 155 m(2)/s at 1,000m and 2637 +/- 311 m(2)/s at the surface, with elevated diffusivities in regions of enhanced eddy kinetic energy, such as western boundary currents and along the Antarctic Circumpolar Current. The eddy kinetic energy at the equator is high at both the surface and depth, but the eddy diffusivity is only enhanced near the surface. At depth the eddy diffusivity is strongly suppressed due to the presence of mean flow. We used our observational estimates to test the validity of an eddy diffusivity parameterization that accounts for mixing suppression in the presence of zonal mean flows. Our results indicated that this parameterization generally agrees with the directly observed eddy diffusivities in the midlatitude and high-latitude oceans.
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Date Issued
2018-07-01
Identifier
FSU_libsubv1_wos_000441888200008, 10.1029/2018JC013750
Format
Citation
Horizontal mixing in the Southern Ocean from Argo float trajectories
Title
Horizontal mixing in the Southern Ocean from Argo float trajectories.
Creator
Roach, Christopher J., Balwada, Dhruv, Speer, Kevin
Abstract/Description
We provide the first observational estimate of the circumpolar distribution of cross-stream eddy diffusivity at 1000 m in the Southern Ocean using Argo float trajectories. We show that Argo float trajectories, from the float surfacing positions, can be used to estimate lateral eddy diffusivities in the ocean and that these estimates are comparable to those obtained from RAFOS floats, where they overlap. Using the Southern Ocean State Estimate (SOSE) velocity fields to advect synthetic...
Show moreWe provide the first observational estimate of the circumpolar distribution of cross-stream eddy diffusivity at 1000 m in the Southern Ocean using Argo float trajectories. We show that Argo float trajectories, from the float surfacing positions, can be used to estimate lateral eddy diffusivities in the ocean and that these estimates are comparable to those obtained from RAFOS floats, where they overlap. Using the Southern Ocean State Estimate (SOSE) velocity fields to advect synthetic particles with imposed behavior that is "Argo-like'' and "RAFOS-like'' diffusivity estimates from both sets of synthetic particles agreed closely at the three dynamically very different test sites, the Kerguelen Island region, the Southeast Pacific Ocean, and the Scotia Sea, and support our approach. Observed cross-stream diffusivities at 1000 m, calculated from Argo float trajectories, ranged between 300 and 2500 m(2) s(-1), with peaks corresponding to topographic features associated with the Scotia Sea, the Kerguelen Plateau, the Campbell Plateau, and the Southeast Pacific Ridge. These observational estimates agree with previous regional estimates from the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) near the Drake Passage, and other estimates from natural tracers (helium), inverse modeling studies, and current meter measurements. These estimates are also compared to the suppressed eddy diffusivity in the presence of mean flows. The comparison suggests that away from regions of strong topographic steering suppression explains both the structure and magnitude of eddy diffusivity but that eddy diffusivities in the regions of topographic steering are greater than what would be theoretically expected and the ACC experiences localized enhanced cross-stream mixing in these regions.
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Date Issued
2016-08
Identifier
FSU_libsubv1_wos_000386912700011, 10.1002/2015JC011440
Format
Citation