Impact of a Warm Ocean Eddy’s Circulation on Hurricane-Induced Sea Surface Cooling with Implications for Hurricane Intensity

Abstract Upper oceanic heat content (OHC) in advance of a hurricane is generally superior to prestorm sea surface temperature (SST) for indicating favorable regions for hurricane intensification and maintenance. OHC is important because a hurricane’s surface winds mix the upper ocean and entrain cooler water into the oceanic mixed layer from below, subsequently cooling the sea surface in the region providing heat energy to the storm. For a given initial SST, increased OHC typically decreases the wind-induced sea surface cooling, and a warm ocean eddy (WCR) has a higher OHC than its surroundings, so conditions typically become more favorable for a hurricane to intensify when the storm’s core encounters a WCR. When considering hurricane intensity, however, one often-neglected aspect of a WCR is its anticyclonic circulation. This circulation may impact the location and magnitude of the hurricane-induced sea surface cooling. Using an ocean model, either prescribed hurricane wind stress or wind stress obtained via coupling to a hurricane model is applied to an initial ocean condition in which the SST is homogeneous, but a WCR is embedded in an otherwise horizontally homogeneous subsurface density field. Based on model experiments, when a WCR is located to the right of the storm track (in the Northern Hemisphere), the interaction of the WCR’s circulation with the hurricane-induced cold wake can cause increased sea surface cooling under the storm core and decreased storm intensity relative to the scenario where no WCR is present at all. Therefore, the presence of a WCR in advance of a hurricane sometimes creates a less favorable condition for hurricane intensification.

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Limitation of One-Dimensional Ocean Models for Coupled Hurricane–Ocean Model Forecasts

Monthly Weather Review ◽

10.1175/2009mwr2863.1 ◽

2009 ◽

Vol 137 (12) ◽

pp. 4410-4419 ◽

Cited By ~ 74

Author(s):

Richard M. Yablonsky ◽

Isaac Ginis

Keyword(s):

North Atlantic Ocean ◽

Three Dimensional ◽

Ocean Model ◽

Sea Surface ◽

Upper Ocean ◽

Surface Cooling ◽

One Dimensional ◽

Sea Surface Cooling ◽

Ocean Models ◽

The One

Abstract Wind stress imposed on the upper ocean by a hurricane can limit the hurricane’s intensity primarily through shear-induced mixing of the upper ocean and subsequent cooling of the sea surface. Since shear-induced mixing is a one-dimensional process, some recent studies suggest that coupling a one-dimensional ocean model to a hurricane model may be sufficient for capturing the storm-induced sea surface temperature cooling in the region providing heat energy to the hurricane. Using both a one-dimensional and a three-dimensional version of the same ocean model, it is shown here that the neglect of upwelling, which can only be captured by a three-dimensional ocean model, underestimates the storm-core sea surface cooling for hurricanes translating at <∼5 m s−1. For hurricanes translating at <2 m s−1, more than half of the storm-core sea surface cooling is neglected by the one-dimensional ocean model. Since the majority of hurricanes in the western tropical North Atlantic Ocean translate at <5 m s−1, the idealized experiments presented here suggest that one-dimensional ocean models may be inadequate for coupled hurricane–ocean model forecasting.

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Enthalpy and Momentum Fluxes during Hurricane Earl Relative to Underlying Ocean Features

Monthly Weather Review ◽

10.1175/mwr-d-13-00277.1 ◽

2015 ◽

Vol 143 (1) ◽

pp. 111-131 ◽

Cited By ~ 46

Author(s):

Benjamin Jaimes ◽

Lynn K. Shay ◽

Eric W. Uhlhorn

Keyword(s):

Thermal Structure ◽

Heat Content ◽

Sea Surface ◽

Atmospheric Environment ◽

Specific Humidity ◽

Intensity Change ◽

Surface Cooling ◽

Near Surface ◽

Sea Surface Cooling

Abstract Using dropsondes from 27 aircraft flights, in situ observations, and satellite data acquired during Tropical Cyclone Earl (category 4 hurricane), bulk air–sea fluxes of enthalpy and momentum are investigated in relation to intensity change and underlying upper-ocean thermal structure. During Earl’s rapid intensification (RI) period, ocean heat content (OHC) variability relative to the 26°C isotherm exceeded 90 kJ cm−2, and sea surface cooling was less than 0.5°C. Enthalpy fluxes of ~1.1 kW m−2 were estimated for Earl’s peak intensity. Daily sea surface heat losses of , , and kJ cm−2 were estimated for RI, mature, and weakening stages, respectively. A ratio of the exchange coefficients of enthalpy (CK) and momentum (CD) between 0.54 and 0.7 produced reliable estimates for the fluxes relative to OHC changes, even during RI; a ratio overestimated the fluxes. The most important result is that bulk enthalpy fluxes were controlled by the thermodynamic disequilibrium between the sea surface and the near-surface air, independently of wind speed. This disequilibrium was strongly influenced by underlying warm oceanic features; localized maxima in enthalpy fluxes developed over tight horizontal gradients of moisture disequilibrium over these eddy features. These regions of local buoyant forcing preferentially developed during RI. The overall magnitude of the moisture disequilibrium (Δq = qs − qa) was determined by the saturation specific humidity at sea surface temperature (qs) rather than by the specific humidity of the atmospheric environment (qa). These results support the hypothesis that intense local buoyant forcing by the ocean could be an important intensification mechanism in tropical cyclones over warm oceanic features.

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Oceanic response to the consecutive Hurricanes Dorian and Humberto (2019) in the Sargasso Sea

10.5194/nhess-2020-296 ◽

2020 ◽

Author(s):

Dailé Avila-Alonso ◽

Jan M. Baetens ◽

Rolando Cardenas ◽

Bernard De Baets

Keyword(s):

Heat Content ◽

Biological Response ◽

Euphotic Zone ◽

Sea Surface ◽

Sargasso Sea ◽

Surface Cooling ◽

Chl A ◽

The Third ◽

Oceanic Response ◽

Sea Surface Cooling

Abstract. Understanding the oceanic response to tropical cyclones (TCs) is of importance for studies on climate change. Although the oceanic effects induced by individual TCs have been extensively investigated, studies on the oceanic response to the passage of consecutive TCs are rare. In this work, we assess the upper oceanic response to the passage of the Hurricanes Dorian and Humberto over the western Sargasso Sea in 2019 using satellite remote sensing and modelled data. We found that the combined effects of these slow-moving TCs led to an increased oceanic response during the third and fourth post-storm weeks of Dorian (accounting for both Dorian and Humberto effects) because of the induced mixing and upwelling at this time. Overall, anomalies of sea surface temperature, ocean heat content and mean temperature from the sea surface to a depth of 100 m were a 50, 63 and 57% smaller (more negative) in the third/fourth post-storm weeks than in the first/second poststorm weeks (accounting only for Dorian effects) of Dorian, respectively, while surface chlorophyll-a (chl-a) concentration anomalies, the mean ch-a concentration in the euphotic zone and the chl-a concentration in the deep chlorophyll maximum were 16, 4 and 16% higher in the third/fourth post-storm weeks than in the first/second post-storm weeks, respectively. The sea surface cooling and increased biological response induced by these TCs were significantly higher (Mann-Whitney test p < 0.05) as compared to climatological records. Our climatological analysis reveals that the strongest TC-induced oceanographic variability in the western Sargasso Sea can be associated with the occurrence of consecutive TCs and long-lasting TC forcing.

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Oceanic response to the consecutive Hurricanes Dorian and Humberto (2019) in the Sargasso Sea

Natural Hazards and Earth System Science ◽

10.5194/nhess-21-837-2021 ◽

2021 ◽

Vol 21 (2) ◽

pp. 837-859

Author(s):

Dailé Avila-Alonso ◽

Jan M. Baetens ◽

Rolando Cardenas ◽

Bernard De Baets

Keyword(s):

Heat Content ◽

Biological Response ◽

Euphotic Zone ◽

Sea Surface ◽

Sargasso Sea ◽

Surface Cooling ◽

Chl A ◽

The Third ◽

Oceanic Response ◽

Sea Surface Cooling

Abstract. Understanding the oceanic response to tropical cyclones (TCs) is of importance for studies on climate change. Although the oceanic effects induced by individual TCs have been extensively investigated, studies on the oceanic response to the passage of consecutive TCs are rare. In this work, we assess the upper-oceanic response to the passage of Hurricanes Dorian and Humberto over the western Sargasso Sea in 2019 using satellite remote sensing and modelled data. We found that the combined effects of these slow-moving TCs led to an increased oceanic response during the third and fourth post-storm weeks of Dorian (accounting for both Dorian and Humberto effects) because of the induced mixing and upwelling at this time. Overall, anomalies of sea surface temperature, ocean heat content, and mean temperature from the sea surface to a depth of 100 m were 50 %, 63 %, and 57 % smaller (more negative) in the third–fourth post-storm weeks than in the first–second post-storm weeks of Dorian (accounting only for Dorian effects), respectively. For the biological response, we found that surface chlorophyll a (chl a) concentration anomalies, the mean chl a concentration in the euphotic zone, and the chl a concentration in the deep chlorophyll maximum were 16 %, 4 %, and 16 % higher in the third–fourth post-storm weeks than in the first–second post-storm weeks, respectively. The sea surface cooling and increased biological response induced by these TCs were significantly higher (Mann–Whitney test, p<0.05) compared to climatological records. Our climatological analysis reveals that the strongest TC-induced oceanographic variability in the western Sargasso Sea can be associated with the occurrence of consecutive TCs and long-lasting TC forcing.

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Metrics of hurricane-ocean interaction: vertically-integrated or vertically-averaged ocean temperature?

Ocean Science Discussions ◽

10.5194/osd-6-909-2009 ◽

2009 ◽

Vol 6 (2) ◽

pp. 909-951 ◽

Cited By ~ 7

Author(s):

J. F. Price

Keyword(s):

Thermal Field ◽

Vertical Mixing ◽

Heat Content ◽

Ocean Temperature ◽

Surface Cooling ◽

Continental Shelves ◽

Hurricane Intensification ◽

Sea Surface Cooling ◽

Integrated Or ◽

High Range

Abstract. The ocean thermal field is often represented in hurricane-ocean interaction by a metric termed the upper Ocean Heat Content (OHC), the vertical integral of ocean temperature in excess of 26°C. High values of OHC have proven useful for identifying ocean regions that are especially favorable for hurricane intensification. Nevertheless, it is argued here that a more direct and robust metric of the ocean thermal field may be afforded by a vertical average of temperature, in one version from the surface to 100 m, a typical depth of vertical mixing by a mature hurricane. OHC and the depth-averaged temperature, dubbed T100, are well correlated over the deep open ocean in the high range of OHC, OHC≥75 kJ cm−2. They are poorly correlated in the low range of OHC, ≤50 kJ cm−2, in part because OHC is degenerate when evaluated on cool ocean temperatures ≤26°C. OHC and T100 can be qualitatively different also over shallow continental shelves: OHC will generally indicate comparatively low values regardless of the ocean temperature, while T100 will take on high values over a shelf that is warm and upwelling neutral or negative, since there will be little cool water that could be mixed into the surface layer. Some limited evidence is that continental shelves may be regions of comparatively small sea surface cooling during a hurricane passage, but more research is clearly required on this important issue.

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On the Use of Ocean Dynamic Temperature for Hurricane Intensity Forecasting

Weather and Forecasting ◽

10.1175/waf-d-17-0143.1 ◽

2018 ◽

Vol 33 (2) ◽

pp. 411-418 ◽

Cited By ~ 8

Author(s):

Karthik Balaguru ◽

Gregory R. Foltz ◽

L. Ruby Leung ◽

Samson M. Hagos ◽

David R. Judi

Keyword(s):

Prediction Models ◽

Vertical Mixing ◽

Model Performance ◽

Heat Content ◽

Sea Surface ◽

Surface Cooling ◽

Hurricane Intensity ◽

Dynamic Temperature ◽

Intensity Prediction ◽

Heat Potential

Abstract Sea surface temperature (SST) and tropical cyclone heat potential (TCHP) are metrics used to incorporate the ocean’s influence on hurricane intensification into the National Hurricane Center’s Statistical Hurricane Intensity Prediction Scheme (SHIPS). While both SST and TCHP serve as useful measures of the upper-ocean heat content, they do not accurately represent ocean stratification effects. Here, it is shown that replacing SST within the SHIPS framework with a dynamic temperature Tdy, which accounts for the oceanic negative feedback to the hurricane’s intensity arising from storm-induced vertical mixing and sea surface cooling, improves the model performance. While the model with SST and TCHP explains about 41% of the variance in 36-h intensity changes, replacing SST with Tdy increases the variance explained to nearly 44%. These results suggest that representation of the oceanic feedback, even through relatively simple formulations such as Tdy, may improve the performance of statistical hurricane intensity prediction models such as SHIPS.

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The Effect of Atmosphere–Ocean Coupling on the Structure and Intensity of Tropical Cyclone Bejisa in the Southwest Indian Ocean

Atmosphere ◽

10.3390/atmos12060688 ◽

2021 ◽

Vol 12 (6) ◽

pp. 688

Author(s):

Soline Bielli ◽

Christelle Barthe ◽

Olivier Bousquet ◽

Pierre Tulet ◽

Joris Pianezze

Keyword(s):

Tropical Cyclone ◽

Mixed Layer ◽

Heat Fluxes ◽

Sea Surface ◽

Ocean Mixed Layer ◽

Surface Cooling ◽

Southwest Indian Ocean ◽

Left Hand ◽

Sea Surface Cooling ◽

The Impact

A set of numerical simulations is relied upon to evaluate the impact of air-sea interactions on the behaviour of tropical cyclone (TC) Bejisa (2014), using various configurations of the coupled ocean-atmosphere numerical system Meso-NH-NEMO. Uncoupled (SST constant) as well as 1D (use of a 1D ocean mixed layer) and 3D (full 3D ocean) coupled experiments are conducted to evaluate the impact of the oceanic response and dynamic processes, with emphasis on the simulated structure and intensity of TC Bejisa. Although the three experiments are shown to properly capture the track of the tropical cyclone, the intensity and the spatial distribution of the sea surface cooling show strong differences from one coupled experiment to another. In the 1D experiment, sea surface cooling (∼1 ∘C) is reduced by a factor 2 with respect to observations and appears restricted to the depth of the ocean mixed layer. Cooling is maximized along the right-hand side of the TC track, in apparent disagreement with satellite-derived sea surface temperature observations. In the 3D experiment, surface cooling of up to 2.5 ∘C is simulated along the left hand side of the TC track, which shows more consistency with observations both in terms of intensity and spatial structure. In-depth cooling is also shown to extend to a much deeper depth, with a secondary maximum of nearly 1.5 ∘C simulated near 250 m. With respect to the uncoupled experiment, heat fluxes are reduced from about 20% in both 1D and 3D coupling configurations. The tropical cyclone intensity in terms of occurrence of 10-m TC wind is globally reduced in both cases by about 10%. 3D-coupling tends to asymmetrize winds aloft with little impact on intensity but rather a modification of the secondary circulation, resulting in a slight change in structure.

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