scholarly journals The Response of Tropical Cyclone Statistics to an Increase in CO2 with Fixed Sea Surface Temperatures

2011 ◽  
Vol 24 (20) ◽  
pp. 5353-5364 ◽  
Author(s):  
Isaac M. Held ◽  
Ming Zhao
Keyword(s):  
Tropical Cyclone ◽  
Vertical Motion ◽  
Atmospheric Model ◽  
Sea Surface ◽  
Intensity Increase ◽  
Average Intensity ◽  
Sea Surface Temperatures ◽  
Global Atmospheric Model ◽  
Relative Contribution ◽  
Surface Temperatures

Abstract The effects on tropical cyclone statistics of doubling CO2, with fixed sea surface temperatures (SSTs), are compared to the effects of a 2-K increase in SST, with fixed CO2, using a 50-km resolution global atmospheric model. Confirming earlier results of Yoshimura and Sugi, a significant fraction of the reduction in globally averaged tropical storm frequency seen in simulations in which both SST and CO2 are increased can be thought of as the effect of the CO2 increase with fixed SSTs. Globally, the model produces a decrease in tropical cyclone frequency of about 10% due to doubling of CO2 and an additional 10% for a 2-K increase in SST, resulting in roughly a 20% reduction when both effects are present. The relative contribution of the CO2 effect to the total reduction is larger in the Northern than in the Southern Hemisphere. The average intensity of storms increases in the model with increasing SST, but intensity remains roughly unchanged, or decreases slightly, with the increase in CO2 alone. As a result, when considering the frequency of more intense cyclones, the intensity increase tends to compensate for the reduced total cyclone numbers for the SST increase in isolation, but not for the CO2 increase in isolation. Changes in genesis in these experiments roughly follow changes in mean vertical motion, reflecting changes in convective mass fluxes. Discussion of one possible perspective on how changes in the convective mass flux might alter genesis rates is provided.

scholarly journals Analysis of an intense bora event in the Adriatic area

2004 ◽  
Vol 4 (2) ◽  
pp. 323-337 ◽  
Author(s):  
D. Cesini ◽  
S. Morelli ◽  
F. Parmiggiani
Keyword(s):  
Satellite Data ◽  
Initial Conditions ◽  
Atmospheric Model ◽  
Horizontal Resolution ◽  
Sea Surface ◽  
Temperature Fields ◽  
Sea Surface Temperatures ◽  
Low Level ◽  
Surface Temperatures ◽  
The Difference

Abstract. Numerical simulations of a bora event, recently occurred in the Adriatic area, are presented. Two reference runs at different horizontal resolution (about 20km and 8km) describe the case. Initial conditions for the atmospheric model integration are obtained from ECMWF analyses. Satellite data are used for comparisons. A further run at horizontal resolution of 8km, using initial satellite sea surface temperatures, is performed to evaluate their impact on the low level wind over the Adriatic Sea. All the simulations are carried out with 50 layers in the vertical. Numerous aspects of the simulations are found to be in agreement with the understanding as well as the observational knowledge of bora distinctive characteristics. Satellite data and model results indicate that a more realistic simulation of the bora wind over the sea is achieved using the model with 8km horizontal resolution and that the low level wind in this case is sensitive, though weakly, to the difference between the used sea surface temperature fields. Simulation results also show that both wind intensity and the area around wind peaks tend to increase when relatively higher sea surface temperatures are used.

scholarly journals Real World and Tropical Cyclone World. Part II: Sensitivity of Tropical Cyclone Formation to Uniform and Meridionally Varying Sea Surface Temperatures under Aquaplanet Conditions

2020 ◽  
Vol 33 (4) ◽  
pp. 1473-1486 ◽  
Author(s):  
K. J. E. Walsh ◽  
S. Sharmila ◽  
M. Thatcher ◽  
S. Wales ◽  
S. Utembe ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Wind Shear ◽  
General Circulation ◽  
Vertical Wind Shear ◽  
Circulation Model ◽  
Static Stability ◽  
Sea Surface ◽  
Sea Surface Temperatures ◽  
Tropical Cyclone Formation ◽  
Surface Temperatures

AbstractThis study aims to investigate the response of simulated tropical cyclone formation to specific climate conditions, using an idealized aquaplanet framework of an ~40-km-horizontal-resolution atmospheric general circulation model. Two sets of idealized model experiments have been performed, one with a set of uniformly distributed constant global sea surface temperatures (SSTs) and another in which varying meridional SST gradients are imposed. The results show that the strongest relationship between climate and tropical cyclone formation is with vertical static stability: increased static stability is strongly associated with decreased tropical cyclone formation. Vertical wind shear and midtropospheric vertical velocity also appear to be related to tropical cyclone formation, although below a threshold value of wind shear there appears to be little relationship. The relationship of tropical cyclone formation with maximum potential intensity and mean sea surface temperature is weak and not monotonic. These simulations strongly suggest that vertical static stability should be part of any climate theory of tropical cyclone formation.

scholarly journals Tropical Cyclone Formation in Environments with Cool SST and High Wind Shear over the Northeastern Atlantic Ocean*

2012 ◽  
Vol 27 (6) ◽  
pp. 1433-1448 ◽  
Author(s):  
Rachel G. Mauk ◽  
Jay S. Hobgood
Keyword(s):  
Tropical Cyclone ◽  
Atlantic Ocean ◽  
Tropical Cyclones ◽  
Wind Shear ◽  
Sea Surface ◽  
Sea Surface Temperatures ◽  
Late Season ◽  
Tropical Cyclone Formation ◽  
Surface Temperatures ◽  
Northeastern Atlantic

Abstract Tropical cyclones with nontropical characteristics are being identified more frequently over the North Atlantic Ocean in recent years. These systems present forecasting challenges because of their hybrid structure. The authors analyze environmental conditions preceding the formation of 20 late-season northeastern Atlantic tropical cyclones identified during the 1975–2005 seasons. A recent tropical storm, Grace (2009), is discussed as a case study. Seventeen of the 20 systems originated from nontropical systems (surface low, frontal weak, and frontal strong). Three tropical cyclones experienced nontropical influences during development despite originating from tropical waves. Ambient sea surface temperatures, relative vorticity, vertical temperature profiles, and wind shear are investigated to identify conditions conducive to tropical cyclone formation. Tropical cyclones developing from nontropical precursors form in environments distinct from the classical tropical cyclone environment. For 17 systems, sea surface temperatures are cooler than 26°C. Stability analysis suggests that convection is shallow. Wind shear decreases for the 850–300-hPa layer in comparison to the 850–200-hPa layer. Most systems still experience shear in excess of 8 m s−1 for the 850–300-hPa layer. It is suggested that late-season tropical cyclones in this region are shallower in vertical extent than typical tropical cyclones, which reduces the impact of strong wind shear in the 850–200-hPa layer.

scholarly journals Response of Tropical Cyclone Frequency to Sea Surface Temperatures Using Aqua-Planet Simulations

Oceans ◽  
2021 ◽  
Vol 2 (4) ◽  
pp. 785-810
Author(s):  
Pavan Harika Raavi ◽  
Kevin J. E. Walsh
Keyword(s):  
Tropical Cyclone ◽  
Mass Flux ◽  
Environmental Conditions ◽  
Global Climate Model ◽  
Static Stability ◽  
Sea Surface ◽  
Sea Surface Temperatures ◽  
Saturation Deficit ◽  
Surface Temperatures ◽  
Tropical Depressions

The present study investigates the effect of increasing sea surface temperatures (SSTs) on tropical cyclone (TC) frequency using the high-resolution Australian Community Climate and Earth-System Simulator (ACCESS) model. We examine environmental conditions leading to changes in TC frequency in aqua-planet global climate model simulations with globally uniform sea surface temperatures (SSTs). Two different TC tracking schemes are used. The Commonwealth Scientific and Industrial Research Organization (CSIRO) scheme (a resolution-dependent scheme) detects TCs that resemble observed storms, while the Okubo–Weiss zeta parameter (OWZP) tracking scheme (a resolution-independent scheme) detects the locations within “marsupial pouches” that are favorable for TC formation. Both schemes indicate a decrease in the global mean TC frequency with increased saturation deficit and static stability of the atmosphere. The OWZP scheme shows a poleward shift in the genesis locations with rising temperatures, due to lower vertical wind shear. We also observe an overall decrease in the formation of tropical depressions (TDs) with increased temperatures, both for those that develop into TCs and non-developing cases. The environmental variations at the time of TD genesis between the developing and the non-developing tropical depressions identify the Okubo–Weiss (OW) parameter and omega (vertical mass flux) as significant influencing variables. Initial vortices with lower vorticity or with weaker upward mass flux do not develop into TCs due to environments with higher saturation deficit and stronger static stability of the atmosphere. The latitudinal variations in the large-scale environmental conditions account for the latitudinal differences in the TC frequency in the OWZP scheme.

Sign in / Sign up

Export Citation Format

Share Document