scholarly journals Tropical cyclone genesis potential across palaeoclimates

2015 ◽  
Vol 11 (10) ◽  
pp. 1433-1451 ◽  
Author(s):  
J. H. Koh ◽  
C. M. Brierley
Keyword(s):  
Carbon Dioxide ◽  
Tropical Cyclone ◽  
Last Glacial Maximum ◽  
Large Scale ◽  
Climate Models ◽  
Glacial Maximum ◽  
Tropical Cyclone Genesis ◽  
Last Glacial ◽  
Potential Index ◽  
Cyclone Genesis

Abstract. The favourability of the mid-Pliocene, Last Glacial Maximum (LGM) and mid-Holocene for tropical cyclone formation is investigated in five climate models. This is measured by a genesis potential index, derived from large-scale atmospheric properties known to be related to storm formation. The mid-Pliocene and Last Glacial Maximum (LGM) were periods where carbon dioxide levels were higher and lower than preindustrial levels respectively, while the mid-Holocene differed primarily in its orbital configuration. The cumulative global genesis potential is found to be fairly invariant across the palaeoclimates in the multi-model mean. Despite this all ensemble members agree on coherent responses in the spatial patterns of genesis potential change. During the mid-Pliocene and LGM, changes in carbon dioxide led to sea surface temperature changes throughout the tropics, yet the potential intensity (a measure associated with maximum tropical cyclone strength) is calculated to be relatively insensitive to these changes. Changes in tropical cyclone genesis potential during the mid-Holocene are found to be asymmetric about the Equator: being reduced in the Northern Hemisphere but enhanced in the Southern Hemisphere. This is clearly driven by the altered seasonal insolation. Nonetheless, the enhanced seasonality drove localised changes in genesis potential, by altering the strength of monsoons and shifting the intertropical convergence zone. Trends in future tropical cyclone genesis potential are consistent neither between the five models studied nor with the palaeoclimate results. It is not clear why this should be the case.

scholarly journals Tropical cyclone genesis across palaeoclimates

2015 ◽  
Vol 11 (1) ◽  
pp. 181-220 ◽  
Author(s):  
J. H. Koh ◽  
C. M. Brierley
Keyword(s):  
Carbon Dioxide ◽  
Tropical Cyclone ◽  
Tropical Cyclones ◽  
Large Scale ◽  
Climate Models ◽  
Tropical Cyclogenesis ◽  
Tropical Cyclone Genesis ◽  
Inter Tropical Convergence Zone ◽  
Potential Index ◽  
Cyclone Genesis

Abstract. Tropical cyclone genesis is investigated for the Pliocene, Last Glacial Maximum (LGM) and the mid-Holocene through analysis of five climate models. The genesis potential index is used to estimate this from large scale atmospheric properties. The mid-Pliocene and LGM characterise periods where carbon dioxide levels were higher and lower than pre-industrial respectively, while the mid-Holocene differed primarily in its orbital configuration. The number of tropical cyclones formed each year is found to be fairly consistent across the various palaeoclimates. Although there is some model uncertainty in the change of global annual tropical cyclone frequency, there are coherent changes in the spatial patterns of tropical cyclogenesis. During the Pliocene and LGM, changes in carbon dioxide led to sea surface temperature changes throughout the tropics, yet the potential intensity of tropical cyclones appears relatively insensitive to these variations. Changes in tropical cyclone genesis during the mid-Holocene are observed to be asymmetric about the Equator: genesis is reduced in the Northern Hemisphere, but enhanced in the Southern Hemisphere. This is clearly driven by the altered seasonal insolation. Nonetheless, the enhanced seasonality may have driven localised effects on tropical cyclone genesis, through changes to the strength of monsoons and shifting of the inter-tropical convergence zone. Trends in future tropical cyclone genesis are neither consistent between the five models studied, nor with the palaeoclimate results. It is not clear why this should be the case.

scholarly journals Tropical Cyclone Genesis Factors in Simulations of the Last Glacial Maximum

2012 ◽  
Vol 25 (12) ◽  
pp. 4348-4365 ◽  
Author(s):  
Robert L. Korty ◽  
Suzana J. Camargo ◽  
Joseph Galewsky
Keyword(s):  
Tropical Cyclone ◽  
Last Glacial Maximum ◽  
Large Scale ◽  
Glacial Maximum ◽  
Tropical Cyclogenesis ◽  
Tropical Cyclone Genesis ◽  
Surface Cooling ◽  
Last Glacial ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract Large-scale environmental factors that favor tropical cyclogenesis are calculated and examined in simulations of the Last Glacial Maximum (LGM) from the Paleoclimate Modelling Intercomparison Project Phase 2 (PMIP2). Despite universally colder conditions at the LGM, values of tropical cyclone potential intensity, which both serves as an upper bound on thermodynamically achievable intensity and indicates regions supportive of the deep convection required, are broadly similar in magnitude to those in preindustrial era control simulation. Some regions, including large areas of the central and western North Pacific, feature higher potential intensities at the LGM than they do in the control runs, while other regions including much of the Atlantic and Indian Oceans are lower. Changes in potential intensity are strongly correlated with the degree of surface cooling during the LGM. Additionally, two thermodynamic parameters—one that measures midtropospheric entropy deficits relevant for tropical cyclogenesis and another related to the time required for genesis—are broadly more favorable in the LGM simulation than in the preindustrial era control. A genesis potential index yields higher values for the LGM in much of the western Pacific, a feature common to nearly all of the individual models examined.

The PMIP4-CMIP6 Last Glacial Maximum experiments: preliminary results and comparison with the PMIP3-CMIP5 simulations

2020 ◽  
Author(s):  
Masa Kageyama ◽  
Keyword(s):  
Last Glacial Maximum ◽  
Ocean Circulation ◽  
Large Scale ◽  
Climate Changes ◽  
Climate Models ◽  
Glacial Maximum ◽  
Meridional Overturning Circulation ◽  
Jet Streams ◽  
Last Glacial ◽  
Simulated Precipitation

<p>The Last Glacial Maximum (LGM, ~21,000 years ago) has been a major focus for evaluating how well state-of-the-art climate models simulate climate changes as large as those expected in the future using paleoclimate reconstructions. A new generation of climate models have been used to generate LGM simulations as part of the Palaeoclimate Modelling Intercomparison Project (PMIP) contributionto CMIP6. Here we provide a preliminary analysis and evaluation of the results of these LGM experiments and compare them with the previous generation of simulations (PMIP3-CMIP5). We show that the PMIP4-CMIP6 are globally less cold and less dry than the PMIP3-CMIP5 simulations, most probably because of the use of a more realistic specification of the northern hemisphere ice sheets in the latest simulations although changes in model configuration may also contribute to this. There are important differences in both atmospheric and ocean circulation between the two sets of experiments, with the northern and southern jet streams being more poleward and the changes in the Atlantic Meridional Overturning Circulation being less pronounced in the PMIP4-CMIP6 simulations than in the PMIP3-CMIP5 simulations. Changes in simulated precipitation patterns are influenced by both temperature and circulation changes. Differences in simulated climate between individual models remain large so, although there are differences in the average behaviour across the two ensembles, the new simulation results are not fundamentally different from the PMIP3-CMIP5 results. Evaluation of large-scale climate features, such as land-sea contrast and polar amplification, confirms that the models capture these well and within the uncertainty of the palaeoclimate reconstructions. Nevertheless, regional climate changes are less well simulated: the models underestimate extratropical cooling, particularly in winter, and precipitation changes. The spatial patterns of increased precipitation associated with changes in the jet streams are also poorly captured. However, changes in the tropics are more realistic, particularly the changes in tropical temperatures over the oceans. Although these results are preliminary in nature, because of the limited number of LGM simulations currently available, they nevertheless point to the utility of using paleoclimate simulations to understand the mechanisms of climate change and evaluate model performance.</p>

scholarly journals Tropical cyclone genesis potential index in climate models

2007 ◽  
Vol 59 (4) ◽  
pp. 428-443 ◽  
Author(s):  
Suzana Camargo ◽  
Adam H. Sobel ◽  
Anthony G. Barnston ◽  
Kerry A. Emanuel
Keyword(s):  
Tropical Cyclone ◽  
Climate Models ◽  
Tropical Cyclone Genesis ◽  
Genesis Potential Index ◽  
Potential Index ◽  
Cyclone Genesis

scholarly journals Results of PMIP2 coupled simulations of the Mid-Holocene and Last Glacial Maximum – Part 1: experiments and large-scale features

2007 ◽  
Vol 3 (2) ◽  
pp. 261-277 ◽  
Author(s):  
P. Braconnot ◽  
B. Otto-Bliesner ◽  
S. Harrison ◽  
S. Joussaume ◽  
J.-Y. Peterchmitt ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Large Scale ◽  
Climate Models ◽  
Glacial Maximum ◽  
Second Phase ◽  
Atmospheric Models ◽  
Last Glacial ◽  
Intercomparison Project ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. A set of coupled ocean-atmosphere simulations using state of the art climate models is now available for the Last Glacial Maximum and the Mid-Holocene through the second phase of the Paleoclimate Modeling Intercomparison Project (PMIP2). This study presents the large-scale features of the simulated climates and compares the new model results to those of the atmospheric models from the first phase of the PMIP, for which sea surface temperature was prescribed or computed using simple slab ocean formulations. We consider the large-scale features of the climate change, pointing out some of the major differences between the different sets of experiments. We show in particular that systematic differences between PMIP1 and PMIP2 simulations are due to the interactive ocean, such as the amplification of the African monsoon at the Mid-Holocene or the change in precipitation in mid-latitudes at the LGM. Also the PMIP2 simulations are in general in better agreement with data than PMIP1 simulations.

scholarly journals Tropical cyclone genesis potential index in climate models

2007 ◽  
Author(s):  
Suzana J. Camargo ◽  
Adam H. Sobel ◽  
Anthony G. Barnston ◽  
Kerry A. Emanuel
Keyword(s):  
Tropical Cyclone ◽  
Climate Models ◽  
Tropical Cyclone Genesis ◽  
Genesis Potential Index ◽  
Potential Index ◽  
Cyclone Genesis

scholarly journals Coupled simulations of the mid-Holocene and Last Glacial Maximum: new results from PMIP2

2006 ◽  
Vol 2 (6) ◽  
pp. 1293-1346 ◽  
Author(s):  
P. Braconnot ◽  
B. Otto-Bliesner ◽  
S. Harrison ◽  
S. Joussaume ◽  
J.-Y. Peterchmitt ◽  
...  
Keyword(s):  
Water Vapour ◽  
Last Glacial Maximum ◽  
Large Scale ◽  
Climate Models ◽  
Glacial Maximum ◽  
Boreal Summer ◽  
Second Phase ◽  
Surface Cooling ◽  
Last Glacial ◽  
Summer Warming

Abstract. A set of coupled ocean-atmosphere simulations using state of the art climate models is now available for the Last Glacial Maximum and the mid-Holocene through the second phase of the Paleoclimate Modeling Intercomparison Project (PMIP2). This study presents the large scale features of the simulated climates and compares the new model results to those of the atmospheric models from the first phase of the PMIP, for which sea surface temperature was prescribed or computed using simple slab ocean formulations. We consider first the large scale features of the climate change, pointing out some of the major differences between the different sets of experiments. Then we quantify the latitudinal shift of the location of the ITCZ in the tropical regions during boreal summer. It is shown that this shift is limited for LGM, whereas a northward shift and an increase of precipitation are well depicted for mid-Holocene in continental regions affected by monsoon precipitation. In the last part we quantify for both periods the feedback from snow and sea-ice in mid and high latitudes. We show that it contributes for half of the cooling in the northern hemisphere for LGM, the second half being achieved by the reduced CO2 and water vapour in the atmosphere. For mid-Holocene the snow and albedo feedbacks strengthen spring cooling and enhance boreal summer warming, whereas water vapour reinforces the late summer warming. These feedbacks are modest in the southern hemisphere. For LGM most of the surface cooling is due to CO2 and water vapour.

Developing versus Nondeveloping Disturbances for Tropical Cyclone Formation. Part II: Western North Pacific

2012 ◽  
Vol 140 (4) ◽  
pp. 1067-1080 ◽  
Author(s):  
Bing Fu ◽  
Melinda S. Peng ◽  
Tim Li ◽  
Duane E. Stevens
Keyword(s):  
Tropical Cyclone ◽  
North Pacific ◽  
Western North Pacific ◽  
Large Scale ◽  
Relative Vorticity ◽  
Tropical Cyclone Genesis ◽  
Horizontal Shear ◽  
The North ◽  
Thermodynamic Variables ◽  
Cyclone Genesis

Global daily reanalysis fields from the Navy Operational Global Atmospheric Prediction System (NOGAPS) are used to analyze Northern Hemisphere summertime (June–September) developing and nondeveloping disturbances for tropical cyclone (TC) formation from 2003 to 2008. This is Part II of the study focusing on the western North Pacific (WNP), following Part I for the North Atlantic (NATL) basin. Tropical cyclone genesis in the WNP shows different characteristics from that in the NATL in both large-scale environmental conditions and prestorm disturbances. A box difference index (BDI) is used to identify parameters in differentiating between the developing and nondeveloping disturbances. In order of importance, they are 1) 800-hPa maximum relative vorticity, 2) rain rate, 3) vertically averaged horizontal shear, 4) vertically averaged divergence, 5) 925–400-hPa water vapor content, 6) SST, and 7) translational speed. The study indicates that dynamic variables are more important in TC genesis in the WNP, while in Part I of the study the thermodynamic variables are identified as more important in the NATL. The characteristic differences between the WNP and the NATL are compared.

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