Future Impact of Differential Interbasin Ocean Warming on Atlantic Hurricanes (original) (raw)
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Quaternary International, 2009
Processes affecting hurricane development over the North Atlantic like the El Niño Southern Oscillation (ENSO), the stratospheric Quasi-Biennial Oscillation (QBO) and Sea Surface Temperatures (SSTs) are discussed. Global coupled climate model simulations cannot answer directly the question on enhancement of hurricane activities (or its absence) under increased greenhouse gas concentrations because of their too coarse resolution. Therefore large-scale quantities that affect hurricane formation are investigated in a future warmer climate.More frequent or more intense hurricanes are expected from an increase in the local SST, from more latent heat flux from the ocean to the atmosphere, from more westerly winds in the tropical stratosphere that reduces the occurrence of strong easterly phases of the QBO and from a more moist-unstable stratification of the atmosphere. However, a stronger vertical wind shear similar to the difference between El Niño and La Niña events suggests fewer hurricanes in the northern Atlantic. Also a more dry-stable atmosphere would lead to fewer hurricanes. Of the various forcing factors, the impact of wind shear appears to be more decisive, i.e. with a strong wind shear over the tropical Atlantic like during El Niño events strong hurricanes hardly happen while impacts from SSTs over the tropical Atlantic are less significant. As there are some factors favouring an increase of hurricane activity in a future climate and others favouring a decrease, it remains so far difficult to estimate their joint effect and to suggest any decisive trend. The area of hurricane development is limited among others by an increase of vertical wind shear towards the north and south from a minimum at 5–10°N. This wind shear pattern does not change in a future climate and has the potential of superseding impacts from ocean warming. A need of very long time-series for obtaining robust results becomes obvious. Here at least 50 years of data were used.
Increased tropical Atlantic wind shear in model projections of global warming
Geophysical Research Letters, 2007
1] To help understand possible impacts of anthropogenic greenhouse warming on hurricane activity, we assess model-projected changes in large-scale environmental factors tied to variations in hurricane statistics. This study focuses on vertical wind shear (V s ) over the tropical Atlantic during hurricane season, the increase of which has been historically associated with diminished hurricane activity and intensity. A suite of state-of-the-art global climate model experiments is used to project changes in V s over the 21st century. Substantial increases in tropical Atlantic and East Pacific shear are robust features of these experiments, and are shown to be connected to the modelprojected decrease in the Pacific Walker circulation. The relative changes in shear are found to be comparable to those of other large-scale environmental parameters associated with Atlantic hurricane activity. The influence of these V s changes should be incorporated into projections of long-term hurricane activity. Citation: Vecchi, G. A., and B. J. Soden , Increased tropical Atlantic wind shear in model projections of global warming, Geophys. Res. Lett., 34, L08702,
Simulated reduction in Atlantic hurricane frequency under twenty-first-century warming conditions
Nature Geoscience, 2008
Atlantic Ocean and measures of Atlantic hurricane activity have been reported to be strongly correlated since at least 1950 (refs 1-5), raising concerns that future greenhouse-gas-induced warming 6 could lead to pronounced increases in hurricane activity. Models that explicitly simulate hurricanes are needed to study the influence of warming ocean temperatures on Atlantic hurricane activity, complementing empirical approaches. Our regional climate model of the Atlantic basin reproduces the observed rise in hurricane counts between 1980 and 2006, along with much of the interannual variability, when forced with observed sea surface temperatures and atmospheric conditions 7 . Here we assess, in our model system 7 , the changes in large-scale climate that are projected to occur by the end of the twenty-first century by an ensemble of global climate models 8 , and find that Atlantic hurricane and tropical storm frequencies are reduced. At the same time, near-storm rainfall rates increase substantially. Our results do not support the notion of large increasing trends in either tropical storm or hurricane frequency driven by increases in atmospheric greenhouse-gas concentrations.
Journal of Climate, 2013
A method of downscaling that isolates the effect of temperature and moisture changes on tropical cyclone (TC) activity was presented in Part I of this study. By applying thermodynamic modifications to analyzed initial and boundary conditions from past TC seasons, initial disturbances and the strength of synoptic-scale vertical wind shear are preserved in future simulations. This experimental design allows comparison of TC genesis events in the same synoptic setting, but in current and future thermodynamic environments. Simulations of both an active (September 2005) and inactive (September 2009) portion of past hurricane seasons are presented.
Impacts from SSTs, ENSO, stratospheric QBO and global warming on Hurricanes over the North Atlantic
Processes affecting hurricane development over the North Atlantic like the El Niño Southern Oscillation (ENSO), the stratospheric Quasi-Biennial Oscillation (QBO) and Sea Surface Temperatures (SSTs) are discussed. Global coupled climate model simulations cannot answer directly the question on enhancement of hurricane activities (or its absence) under increased greenhouse gas concentrations because of their too coarse resolution. Therefore large-scale quantities that affect hurricane formation are investigated in a future warmer climate. More frequent or more intense hurricanes are expected from an increase in the local SST, from more latent heat flux from the ocean to the atmosphere, from more westerly winds in the tropical stratosphere that reduces the occurrence of strong easterly phases of the QBO and from a more moist-unstable stratification of the atmosphere. However, a stronger vertical wind shear similar to the difference between El Niño and La Niña events suggests fewer hurr...
Impacts of non-canonical El Niño patterns on Atlantic hurricane activity
Geophysical Research Letters, 2012
The impact of non-canonical El Niño patterns, typically characterized by warmer than normal sea surface temperatures (SSTs) in the central tropical Pacific, on Atlantic tropical cyclone (TC) is explored by using composites of key Atlantic TC indices and tropospheric vertical wind shear over the Atlantic main development region (MDR). The highlight of our major findings is that, while the canonical El Niño pattern has a strong suppressing influence on Atlantic TC activity, non-canonical El Niño patterns considered in this study, namely central Pacific warming, El Niño Modoki, positive phase Trans-Niño, and positive phase Pacific meridional mode, all have insubstantial impact on Atlantic TC activity. This result becomes more conclusive when the impact of MDR SST is removed from the Atlantic TC indices and MDR wind shear by using the method of linear regression. Further analysis suggests that the tropical Pacific SST anomalies associated with the non-canonical El Niño patterns are not strong enough to cause a substantial warming of the tropical troposphere in the Atlantic region, which is the key factor that increases the wind shear and atmospheric static stability over the MDR. During the recent decades, the non-canonical El Niños have been more frequent while the canonical El Niño has been less frequent. If such a trend continues in the future, it is expected that the suppressing effect of El Niño on Atlantic TC activity will diminish and thus the MDR SST will play a more important role in controlling Atlantic TC activity in the coming decades.
Sea Surface Temperature Variability in Hurricanes: Implications with Respect to Intensity Change
Monthly Weather Review, 2003
Scientists at NOAA's Hurricane Research Division recently analyzed the inner-core upper-ocean environment for 23 Atlantic, Gulf of Mexico, and Caribbean hurricanes between 1975 and 2002. The interstorm variability of sea surface temperature (SST) change between the hurricane inner-core environment and the ambient ocean environment ahead of the storm is documented using airborne expendable bathythermograph (AXBT) observations and buoy-derived archived SST data. The authors demonstrate that differences between inner-core and ambient SST are much less than poststorm, ''cold wake'' SST reductions typically observed (i.e., ϳ0Њ-2ЊC versus 4Њ-5ЊC). These findings help define a realistic parameter space for storm-induced SST change within the important high-wind inner-core hurricane environment. Results from a recent observational study yielded estimates of upper-ocean heat content, upper-ocean energy extracted by the storm, and upper-ocean energy utilization for a wide range of tropical systems. Results from this analysis show that, under most circumstances, the energy available to the tropical cyclone is at least an order of magnitude greater than the energy extracted by the storm. This study also highlights the significant impact that changes in inner-core SST have on the magnitude of airsea fluxes under high-wind conditions. Results from this study illustrate that relatively modest changes in innercore SST (order 1ЊC) can effectively alter maximum total enthalpy (sensible plus latent heat) flux by 40% or more.
Modeled impact of anthropogenic warming on the frequency of intense Atlantic hurricanes
Science (New York, N.Y.), 2010
Several recent models suggest that the frequency of Atlantic tropical cyclones could decrease as the climate warms. However, these models are unable to reproduce storms of category 3 or higher intensity. We explored the influence of future global warming on Atlantic hurricanes with a downscaling strategy by using an operational hurricane-prediction model that produces a realistic distribution of intense hurricane activity for present-day conditions. The model projects nearly a doubling of the frequency of category 4 and 5 storms by the end of the 21st century, despite a decrease in the overall frequency of tropical cyclones, when the downscaling is based on the ensemble mean of 18 global climate-change projections. The largest increase is projected to occur in the Western Atlantic, north of 20 degrees N.
Journal of Climate, 2012
A tropical cyclone–permitting global atmospheric model is used to explore the hurricane frequency response to sea surface temperature (SST) anomalies generated by coupled models for the late-twenty-first century. Results are presented for SST anomalies averaged over 18 models as well as from 8 individual models. For each basin, there exists large intermodel spread in the magnitude and even the sign of the frequency response among the different SST projections. These sizable variations in response are explored to understand features of SST distributions that are important for the basin-wide hurricane responses. In the North Atlantic, the eastern Pacific, and the southern Indian basins, most (72%–86%) of the intermodel variance in storm frequency response can be explained by a simple relative SST index defined as a basin’s storm development region SST minus the tropical mean SST. The explained variance is significantly lower in the South Pacific (48%) and much lower in the western Pac...