The Sensitivity of Tropical Cyclone Activity to Off-Equatorial Thermal Forcing in Aquaplanet Simulations

Ballinger, Andrew; Merlis, Timothy M.; Held, Isaac M.; Zhao, Ming

doi:10.1175/jas-d-14-0284.1

Cited by 34 publications

(54 citation statements)

References 40 publications

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“…A northward shift in GPI is noticeable in the eastern North Pacific, unsurprisingly associated with the local shift in ITCZ. This shift in the ITCZ would be expected to not only impact the genesis of storms (Merlis et al, 2013) but also their intensity (Ballinger et al, 2015). A slight decrease in genesis potential is seen in the North Atlantic.…”

Section: Mid-holocenementioning

confidence: 99%

Tropical cyclone genesis potential across palaeoclimates

Koh

Brierley

2015

Clim. Past

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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.

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Section: Mid-holocenementioning

confidence: 99%

Tropical cyclone genesis potential across palaeoclimates

Koh

Brierley

2015

Clim. Past

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“…SST gradient in the tropics and a lower SST at the poles compared to idealized aquaplanet simulations of Li et al (2013) and Ballinger et al (2015). The former difference yields a larger number of tropical cyclones, while the latter mimics the effect of absent sea ice.…”

Section: Experimental Designmentioning

confidence: 86%

Nonlocality of Tropical Cyclone Activity in Idealized Climate Simulations

Frisius¹,

Abdullah

2017

J Adv Model Earth Syst

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The response of tropical cyclone activity in the predicted warmer future climate is still a topic of scientific research. However, by the nonlocality hypothesis, tropical cyclone activity depends rather on relative than absolute sea surface temperature (SST). This hypothesis is investigated through idealized experiments performed with the global atmospheric climate model PlaSim. The model includes a prescribed SST and adopts a spectral resolution of T170 for resolving tropical cyclones. An idealized land‐sea configuration with two oceans and two continents has been used to study the nonlocality mechanism. The sensitivity experiments WARMBASIN and COLDBASIN include a positive and negative SST anomaly of 2.5 K in the northeastern basin. The tropical cyclone activity in the control run is similar in all four ocean basins while experiment WARMBASIN simulates a striking local increase of tropical cyclones. However, they nearly vanish in the other three ocean basins. The response is weaker and in the opposite way in COLDBASIN with a local reduction and a nonlocal increase. Analysis of well‐known cyclogenesis indices shows that nonlocality could be explained by the vorticity, relative humidity, and upper tropospheric temperature changes in experiment WARMBASIN while only vorticity is in agreement with nonlocality in experiment COLDBASIN. The vorticity anomalies determine the presence or absence of a steady state large‐scale low at the location where tropical cyclones favorably form. This low is modified by an SST‐induced change of a Walker‐like planetary circulation.

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“…The increase, which averages~3.7 TCs per season (August-October), is mainly associated with an increase of TC formation in the subtropics between 30°N and 40°N. Earlier studies suggested that such an increase of subtropical activity could occur with a reduced meridional gradient of the extratropical SST (Ballinger et al, 2015;Fedorov et al, 2018) or a globally warmed climate (e.g., Yoshida et al, 2017). The development of these TCs may be related to subtropical cyclones (Guishard et al, 2009;Bentley et al, 2016), which contributed nearly 50% of TCs in the recent 2018 hurricane season.…”

Section: Summary and Discussionmentioning

confidence: 98%

“…TC formation in the subtropics potentially can cause unexpected damage in regions where TC activity is usually rare (e.g., Hurricane Leslie). Earlier studies suggested that such an increase of subtropical activity could occur with a reduced meridional gradient of the extratropical SST (Ballinger et al, 2015;Fedorov et al, 2018) or a globally warmed climate (e.g., Yoshida et al, 2017).…”

Section: Summary and Discussionmentioning

confidence: 99%

Impacts of Extratropical Weather Perturbations on Tropical Cyclone Activity: Idealized Sensitivity Experiments With a Regional Atmospheric Model

Zhang

Knutson

Garner

2019

Geophysical Research Letters

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Extratropical weather perturbations have been linked to Atlantic tropical cyclones (TCs) activity in observations. However, modeling studies of the extratropical impact are scarce and disagree about its importance and climate implications. Using a nonhydrostatic regional atmospheric model, we explore the extratropical impact by artificially suppressing extratropical weather perturbations at the tropical-extratropical interface. Our 22-year simulations of August-October suggest that the extratropical suppression adds~3.7 Atlantic TCs per season on average, although the response varies among individual years. The TC response mainly appears within 30-40°N, where tropical cyclogenesis frequency quadruples compared to control simulations. This increased cyclogenesis, accompanied by a strong increase of midtropospheric relative humidity, arises as the perturbation suppression reduces the extratropical interference of TC development. The suppression of extratropical perturbations is highly idealized but may suggest mechanisms by which extratropical atmospheric variability potentially influences TC activity in past or future altered climate states. Plain Language SummaryRecent observational studies suggest that Atlantic hurricane activity is strongly affected by extratropical weather processes, but modeling studies disagree about the importance of such an impact. Using a regional atmospheric model, we conduct idealized experiments to explore the extratropical impact on Atlantic hurricane activity. Our simulations of 22 hurricane seasons show that artificially suppressing extratropical weather perturbations at the northern boundary in the model can increase hurricane activity significantly. The response of the model's hurricane activity varies from season to season, which may contribute to the different responses found among earlier modeling studies. Notably, the strongest response of hurricane activity appears within 30-40°N, where the number of hurricane formations quadruples compared to reference simulations. The perturbation reduction also helps hurricanes to move more slowly and smoothly with fewer disruptions from the high latitudes. These experiments, though idealized, suggest that the extratropical atmospheric circulation plays an important moderating role in limiting Atlantic hurricane formation. These experiments also could have implications for hurricane activity in the distant past or in coming decades, for example, if climate warming were accompanied by a weakening or poleward shift of extratropical weather systems.

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The Sensitivity of Tropical Cyclone Activity to Off-Equatorial Thermal Forcing in Aquaplanet Simulations

Cited by 34 publications

References 40 publications

Tropical cyclone genesis potential across palaeoclimates

Tropical cyclone genesis potential across palaeoclimates

Nonlocality of Tropical Cyclone Activity in Idealized Climate Simulations

Impacts of Extratropical Weather Perturbations on Tropical Cyclone Activity: Idealized Sensitivity Experiments With a Regional Atmospheric Model

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