Impact of CO₂-Induced Warming on Simulated Hurricane Intensity and Precipitation: Sensitivity to the Choice of Climate Model and Convective Parameterization

Abstract

Previous studies have found that idealized hurricanes, simulated under warmer, high-CO 2 conditions, are more intense and have higher precipitation rates than under present-day conditions. The present study explores the sensitivity of this result to the choice of climate model used to define the CO 2-warmed environment and to the choice of convective parameterization used in the nested regional model that simulates the hurricanes. Approximately 1300 five-day idealized simulations are performed using a higher-resolution version of the GFDL hurricane prediction system (grid spacing as fine as 9 km, with 42 levels). All storms were embedded in a uniform 5 m s Ϫ1 easterly background flow. The large-scale thermodynamic boundary conditions for the experimentsatmospheric temperature and moisture profiles and SSTs-are derived from nine different Coupled Model Intercomparison Project (CMIP2ϩ) climate models. The CO 2-induced SST changes from the global climate models, based on 80-yr linear trends from ϩ1% yr Ϫ1 CO 2 increase experiments, range from about ϩ0.8Њ to ϩ2.4ЊC in the three tropical storm basins studied. Four different moist convection parameterizations are tested in the hurricane model, including the use of no convective parameterization in the highest resolution inner grid. Nearly all combinations of climate model boundary conditions and hurricane model convection schemes show a CO 2induced increase in both storm intensity and near-storm precipitation rates. The aggregate results, averaged across all experiments, indicate a 14% increase in central pressure fall, a 6% increase in maximum surface wind speed, and an 18% increase in average precipitation rate within 100 km of the storm center. The fractional change in precipitation is more sensitive to the choice of convective parameterization than is the fractional change of intensity. Current hurricane potential intensity theories, applied to the climate model environments, yield an average increase of intensity (pressure fall) of 8% (Emanuel) to 16% (Holland) for the high-CO 2 environments. Convective available potential energy (CAPE) is 21% higher on average in the high-CO 2 environments. One implication of the results is that if the frequency of tropical cyclones remains the same over the coming century, a greenhouse gas-induced warming may lead to a gradually increasing risk in the occurrence of highly destructive category-5 storms.

Regional model simulation of North Atlantic cyclones: Present climate and idealized response to increased sea surface temperature

“…It is worth noting that the increase in mean and extreme precipitation related to the tropical storms is more pronounced than the increase in the maximum wind speed, which is consistent with previous findings [e.g., Knutson and Tuleya, 2004].…”

“…Using estimation strategies to determine the maximum potential intensity of tropical storms based on thermodynamic and dynamic considerations [e.g., Emanuel, 1987;Holland, 1997] might be an alternative, but it lacks some important processes such as ocean spray feedback or upper ocean layer response. Knutson and Tuleya [2004] performed idealized high resolution simulations with the GFDL hurricane prediction system using large-scale thermodynamic boundary conditions from different GCMs. Their results suggest that the risk in the occurrence of highly destructive tropical storms may increase; the maximum wind speed (W max ) and the maximum precipitation rate associated with hurricanes might considerably increase in a future warmer world.…”

Recent slowdown of tropical upper tropospheric warming associated with Pacific climate variability

“…Recent and future changes in the tropical upper tropospheric temperature (T TUT ) have received particular attention [e.g., Santer et al, 2005;Allen and Sherwood, 2008;Thorne et al, 2011;O'Gorman and Singh, 2013;Flannaghan et al, 2014] because they play important roles regarding climate feedbacks and climate sensitivity [e.g., Colman, 2001;Soden and Held, 2006;Vial et al, 2013], atmospheric circulation [e.g., Knutson and Manabe, 1995;Ueda et al, 2006;Vecchi and Soden, 2007], and tropical cyclone activity in a warming climate [e.g., Shen et al, 2000;Knutson and Tuleya, 2004;Emanuel et al, 2013;Vecchi et al, 2013].…”

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

“…Recent studies (Sugi et al, 2002;Oouchi et al, 2006;Yoshimura et al, 2006;Bengtsson et al, 2007) have utilized GCMs to reproduce TC activity and to predict the level of TC activity in warmer climates. To improve upon the coarse resolution employed by GCMs, regional downscaling, in which a regional model is driven by GCM boundary conditions, has been applied to the problem (Knutson and Manabe, 1998;Knutson and Tuleya, 2004;Knutson et al, 2007Knutson et al, , 2008. Another approach is that of Emanuel (2006a) and Emanuel et al (2008, hereafter E08), in which the climate state is randomly seeded with nascent TCs that move according to a beta-and-advection model and whose intensity evolution is determined by a simple but highresolution coupled TC model.…”