Climate change exacerbates hurricane flood hazards along US Atlantic and Gulf Coasts in spatially varying patterns

One of the most destructive natural hazards, tropical cyclone (TC)–induced coastal flooding, will worsen under climate change. Here we conduct climatology–hydrodynamic modeling to quantify the effects of sea level rise (SLR) and TC climatology change (under RCP 8.5) on late 21st century flood hazards at the county level along the US Atlantic and Gulf Coasts. We find that, under the compound effects of SLR and TC climatology change, the historical 100-year flood level would occur annually in New England and mid-Atlantic regions and every 1–30 years in southeast Atlantic and Gulf of Mexico regions in the late 21st century. The relative effect of TC climatology change increases continuously from New England, mid-Atlantic, southeast Atlantic, to the Gulf of Mexico, and the effect of TC climatology change is likely to be larger than the effect of SLR for over 40% of coastal counties in the Gulf of Mexico.National Science Foundation (U.S.) (Grant EAR-1520683

Convective adjustment in baroclinic atmospheres

Local convection in planetary atmospheres is generally considered to result from the action of gravity on small regions of anomalous density. That in rotating baroclinic fluids the total potential energy for small scale convection contains a centrifugal as well as a gravitational contribution is shown. Convective adjustment in such an atmosphere results in the establishment of near adiabatic lapse rates of temperature along suitably defined surfaces of constant angular momentum, rather than in the vertical. This leads in general to sub-adiabatic vertical lapse rates. That such an adjustment actually occurs in the earth's atmosphere is shown by example and the magnitude of the effect for several other planetary atmospheres is estimated

The impact of climate change on hurricane damages in the United States

This paper quantifies hurricane damage caused by climate change across the US. A damage function is estimated from historic hurricane data to measure the impacts at each location given the storm's strength. The minimum barometric pressure of each storm turns out to be a better indicator of damages than the traditional measure of maximum wind speed. A hurricane generator in the Atlantic Ocean is then used to create 5000 storms with and without climate change. Combining the location and intensity of each storm with the income and population projected for each location, it is possible to estimate a detailed picture of how hurricanes will impact each state with and without climate change. Income and population growth alone increase expected baseline damage from $9 to$27 billion per year by 2100. Climate change is expected to increase damage by another $40 billion. Over 85 percent of these impacts are in Florida and the Gulf states. The 10 percent most damaging storms cause 93 percent of expected damage.Climate Change Economics,Climate Change Mitigation and Green House Gases,Hazard Risk Management,Science of Climate Change,Global Environment Facility

The impact of climate change on global tropical storm damages

This paper constructs an integrated assessment model of tropical cyclones in order to quantify the impact that climate change may have on tropical cyclone damages in countries around the world. The paper relies on a tropical cyclone generator in each ocean and several climate models to predict tropical cyclones with and without climate change. A damage model is constructed to compute the resulting damage when a cyclone strikes each country. Economic development is expected to double global tropical cyclone damages because more will be in harm's way. Climate change is expected to double global damage again, causing an additional $54 billion of damage per year. The damage is projected to be concentrated in North America and eastern Asia but many Caribbean islands will suffer the highest damages per unit of GDP. Most of the increased damage will be caused by rare but very powerful storms.Climate Change Economics,Climate Change Mitigation and Green House Gases,Hazard Risk Management,Science of Climate Change,Global Environment Facility

Will Global Warming Make Hurricane Forecasting More Difficult?

Hurricane track forecasts have improved steadily over the past few decades, yet forecasting hurricane intensity remains challenging. Of special concern are the rare instances of tropical cyclones that intensify rapidly just before landfall, catching forecasters and populations off guard, thereby risking large casualties. Here, we review two historical examples of such events and use scaling arguments and models to show that rapid intensification just before landfall is likely to become increasingly frequent and severe as the globe warms.National Science Foundation (U.S.) (Grant AGS-1520683

Stratospheric Modulation of the MJO through Cirrus Cloud Feedbacks

Recent observations have indicated significant modulation of the Madden Julian Oscillation (MJO) by the phase of the stratospheric Quasi-Biennial Oscillation (QBO) during boreal winter. Composites of the MJO show that upper tropospheric ice cloud fraction and water vapor anomalies are generally collocated, and that an eastward tilt with height in cloud fraction exists. Through radiative transfer calculations, it is shown that ice clouds have a stronger tropospheric radiative forcing than do water vapor anomalies, highlighting the importance of incorporating upper tropospheric/lower stratospheric processes into simple models of the MJO. The coupled troposphere-stratosphere linear model previously developed by the authors is extended by including a mean wind in the stratosphere and a prognostic equation for cirrus clouds, which are forced dynamically and allowed to modulate tropospheric radiative cooling, similar to the effect of tropospheric water vapor in previous formulations. Under these modifications, the model still produces a slow, eastward propagating mode that resembles the MJO. The sign of zonal mean wind in the stratosphere is shown to control both the upward wave propagation and tropospheric vertical structure of the mode. Under varying stratospheric wind and interactive cirrus cloud radiation, the MJO-like mode has weaker growth rates under stratospheric westerlies than easterlies, consistent with the observed MJO-QBO relationship. These results are directly attributable to an enhanced barotropic mode under QBO easterlies. It is also shown that differential zonal advection of cirrus clouds leads to weaker growth rates under stratospheric westerlies than easterlies. Implications and limitations of the linear theory are discussed

Upwards Tropospheric Influence on Tropical Stratospheric Upwelling

The response of the stratosphere to a steady geopotential forcing is considered in two separate theoretical models. Solutions to the linearized quasi-geostrophic potential vorticity equations are first used to show that the vertical length scale of a tropopause geopotential anomaly is initially shallow, but significantly increased by diabatic heating from radiative relaxation. This process is deemed as geostrophic adjustment of the stratosphere to tropospheric forcing. Idealized, time-dependent calculations show that tropopause geopotential anomalies can appreciably rise in the stratosphere on time scales of a couple months. A previously developed, coupled troposphere-stratosphere model is introduced and modified to further understand how tropospheric geopotential forcing can induce upwelling in the stratosphere. Solutions to steady, zonally-symmetric sea-surface-temperature forcings in the linear $\beta$-plane model show that the upwards stratospheric penetration of the thermally induced tropopause geopotential anomaly is controlled by a non-dimensional parameter that depends on the ratio between the time scale of wave-drag to that of radiation. It is also shown that the horizontal scale of the tropopause geopotential anomaly modulates the vertical scale of the anomaly. When Earth-like non-dimensional parameters are used, the theoretical model predicts stratospheric temperature anomalies around two times larger in magnitude than those in the boundary layer, approximately in line with observational data. The results are argued to show that wave-drag alone may not suffice to explain certain observed features of the lower stratosphere, foremost of which is the anti-correlation between sea-surface temperature and lower stratospheric temperature

Are Special Processes at Work in the Rapid Intensification of Tropical Cyclones?

Probably not. Frequency distributions of intensification and dissipation developed from synthetic open-ocean tropical cyclone data show no evidence of significant departures from exponential distributions, though there is some evidence for a fat tail of dissipation rates. This suggests that no special factors govern high intensification rates and that tropical cyclone intensification and dissipation are controlled by statistically random environmental and internal variability.National Science Foundation (U.S.) (Grant AGS1032244

Grey swan tropical cyclones

We define ‘grey swan’ tropical cyclones as high-impact storms that would not be predicted based on history but may be foreseeable using physical knowledge together with historical data. Here we apply a climatological–hydrodynamic method to estimate grey swan tropical cyclone storm surge threat for three highly vulnerable coastal regions. We identify a potentially large risk in the Persian Gulf, where tropical cyclones have never been recorded, and larger-than-expected threats in Cairns, Australia, and Tampa, Florida. Grey swan tropical cyclones striking Tampa, Cairns and Dubai can generate storm surges of about 6 m, 5.7 m and 4 m, respectively, with estimated annual exceedance probabilities of about 1/10,000. With climate change, these probabilities can increase significantly over the twenty-first century (to 1/3,100–1/1,100 in the middle and 1/2,500–1/700 towards the end of the century for Tampa). Worse grey swan tropical cyclones, inducing surges exceeding 11 m in Tampa and 7 m in Dubai, are also revealed with non-negligible probabilities, especially towards the end of the century