On the Hyperbolicity of the Bulk Air–Sea Heat Flux Functions: Insights into the Efficiency of Air–Sea Moisture Disequilibrium for Tropical Cyclone Intensification

AbstractSea-to-air heat fluxes are the energy source for tropical cyclone (TC) development and maintenance. In the bulk aerodynamic formulas, these fluxes are a function of surface wind speed U10 and air–sea temperature and moisture disequilibrium (ΔT and Δq, respectively). Although many studies have explained TC intensification through the mutual dependence between increasing U10 and increasing sea-to-air heat fluxes, recent studies have found that TC intensification can occur through deep convective vortex structures that obtain their local buoyancy from sea-to-air moisture fluxes, even under conditions of relatively low wind. Herein, a new perspective on the bulk aerodynamic formulas is introduced to evaluate the relative contribution of wind-driven (U10) and thermodynamically driven (ΔT and Δq) ocean heat uptake. Previously unnoticed salient properties of these formulas, reported here, are as follows: 1) these functions are hyperbolic and 2) increasing Δq is an efficient mechanism for enhancing the fluxes. This new perspective was used to investigate surface heat fluxes in six TCs during phases of steady-state intensity (SS), slow intensification (SI), and rapid intensification (RI). A capping of wind-driven heat uptake was found during periods of SS, SI, and RI. Compensation by larger values of Δq > 5 g kg−1 at moderate values of U10 led to intense inner-core moisture fluxes of greater than 600 W m−2 during RI. Peak values in Δq preferentially occurred over oceanic regimes with higher sea surface temperature (SST) and upper-ocean heat content. Thus, increasing SST and Δq is a very effective way to increase surface heat fluxes—this can easily be achieved as a TC moves over deeper warm oceanic regimes.

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Evaluation of Moist Static Energy in a Simulated Tropical Cyclone

Atmosphere ◽

10.3390/atmos10060319 ◽

2019 ◽

Vol 10 (6) ◽

pp. 319

Author(s):

Lijun Yu ◽

Shuhui Wu ◽

Zhanhong Ma

Keyword(s):

Tropical Cyclone ◽

Potential Temperature ◽

Surface Heat ◽

Heat Fluxes ◽

Moist Static Energy ◽

Surface Heat Fluxes ◽

Budget Analysis ◽

Study Results ◽

Static Energy ◽

Radial Outflow

The characteristics of moist static energy (MSE) and its budget in a simulated tropical cyclone (TC) are examined in this study. Results demonstrate that MSE in a TC system is enhanced as the storm strengthens, primarily because of two mechanisms: upward transfer of surface heat fluxes and subsequent warming of the upper troposphere. An inspection of the interchangeable approximation between MSE and equivalent potential temperature (θe) suggests that although MSE is capable of capturing overall structures of θe, some important features will still be distorted, specifically the low-MSE pool outside the eyewall. In this low-MSE region, from the budget analysis, the discharge of MSE in the boundary layer may even surpass the recharge of MSE from the ocean. Unlike the volume-averaged MSE, the mass-weighted MSE in a fixed volume following the TC shows no apparent increase as the TC intensifies, because the atmosphere becomes continually thinner accompanying the warming of the storm. By calculating a mass-weighted volume MSE budget, the TC system is found to export MSE throughout its lifetime, since the radial outflow overwhelms the radial inflow. Moreover, the more intensified the TC is, the more export of MSE there tends to be. The input of MSE by surface heat fluxes is roughly balanced by the combined effects of radiation and lateral export, wherein a great majority of the imported MSE is reduced by radiation, while the export of MSE from the TC system to the environment accounts for only a small portion.

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The Impact of Outer-Core Surface Heat Fluxes on the Convective Activities and Rapid Intensification of Tropical Cyclones

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-19-0348.1 ◽

2020 ◽

Vol 77 (11) ◽

pp. 3907-3927

Author(s):

Chin-Hsuan Peng ◽

Chun-Chieh Wu

Keyword(s):

Inner Core ◽

Surface Wind ◽

Outer Core ◽

Surface Heat ◽

Heat Fluxes ◽

Intensity Change ◽

Rapid Intensification ◽

Core Surface ◽

Surface Heat Fluxes ◽

The Impact

AbstractThe rapid intensification (RI) of Typhoon Soudelor (2015) is simulated using a full-physics model. To investigate how the outer-core surface heat fluxes affect tropical cyclone (TC) structure and RI processes, a series of numerical experiments are performed by suppressing surface heat fluxes between various radii. It is found that a TC would become quite weaker when the surface heat fluxes are suppressed outside the radius of 60 or 90 km [the radius of maximum surface wind in the control experiment (CTRL) at the onset of RI is roughly 60 km]. However, interestingly, the TC would experience stronger RI when the surface heat fluxes are suppressed outside the radius of 150 km. For those sensitivity experiments with capped surface heat fluxes, the members with greater intensification rate show stronger inner-core mid- to upper-level updrafts and higher heating efficiency prior to the RI periods. Although the outer-core surface heat fluxes in these members are suppressed, the inner-core winds become stronger, extracting more ocean energy from the inner core. Greater outer-core low-level stability in these members results in aggregation of deep convection and subsequent generation and concentration of potential vorticity inside the inner core, thus confining the strongest winds therein. The abovementioned findings are also supported by partial-correlation analyses, which reveal the positive correlation between the inner-core convection and subsequent 6-h intensity change, and the competition between the inner-core and outer-core convections (i.e., eyewall and outer rainbands).

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Long-term global ocean heat content change driven by sub-polar surface heat fluxes

10.1002/essoar.10504695.1 ◽

2020 ◽

Author(s):

Taimoor Sohail ◽

Damien B Irving ◽

Jan David Zika ◽

Ryan M Holmes ◽

John Alexander Church

Keyword(s):

Heat Content ◽

Surface Heat ◽

Heat Fluxes ◽

Ocean Heat Content ◽

Global Ocean ◽

Polar Surface ◽

Surface Heat Fluxes ◽

Content Change

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Fifty Year Trends in Global Ocean Heat Content Traced to Surface Heat Fluxes in the Sub‐Polar Ocean

Geophysical Research Letters ◽

10.1029/2020gl091439 ◽

2021 ◽

Vol 48 (8) ◽

Author(s):

Taimoor Sohail ◽

Damien B. Irving ◽

Jan D. Zika ◽

Ryan M. Holmes ◽

John A. Church

Keyword(s):

Heat Content ◽

Surface Heat ◽

Heat Fluxes ◽

Ocean Heat Content ◽

Global Ocean ◽

Surface Heat Fluxes ◽

Polar Ocean

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Seasonal mixed layer heat budget in coastal waters off Angola

10.5194/egusphere-egu21-6122 ◽

2021 ◽

Author(s):

Mareike Körner ◽

Peter Brandt ◽

Marcus Dengler

Keyword(s):

Mixed Layer ◽

Heat Budget ◽

Heat Content ◽

Nutrient Supply ◽

Surface Heat ◽

Heat Fluxes ◽

Driving Mechanism ◽

Near Surface ◽

Surface Heat Fluxes ◽

Mixed Layer Heat Budget

<p>The Angolan shelf system represents a highly productive ecosystem that exhibits pronounced seasonal variability. Productivity peaks in austral winter when seasonally prevailing upwelling favorable winds are weakest. Thus, other processes than local wind-driven upwelling contribute to the near-coastal cooling and nutrient supply during this season. Possible processes that lead to changes of the mixed-layer heat content does not only include local mechanism but also the passage of remotely forced coastally trapped waves. Understanding the driving mechanism of changes in the mixed-layer heat content that may be locally or remotely forced are vital for understanding of upward nutrient supply and biological productivity off Angola. Here, we investigate the seasonal mixed layer heat budget by analyzing atmospheric and oceanic causes for heat content variability. We calculate monthly estimates of surface heat fluxes, horizontal advection from near-surface velocities, horizontal eddy advection, and vertical entrainment. Additionally, diapycnal heat fluxes at the mixed-layer base are determined from shipboard and glider microstructure data. The results are discussed in reference to the variability of the eastern boundary circulation, surface heat fluxes and wind forcing.</p>

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Surface heat fluxes and subsurface heat content at a site over the southeastern Bering Sea shelf, May–July 1996

Deep Sea Research Part II Topical Studies in Oceanography ◽

10.1016/s0967-0645(02)00325-9 ◽

2002 ◽

Vol 49 (26) ◽

pp. 5911-5917 ◽

Cited By ~ 7

Author(s):

R.K. Reed ◽

P.J. Stabeno

Keyword(s):

Bering Sea ◽

Heat Content ◽

Surface Heat ◽

Heat Fluxes ◽

Surface Heat Fluxes ◽

A Site ◽

Bering Sea Shelf

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Ocean Heat Uptake and Interbasin Transport of the Passive and Redistributive Components of Surface Heating

Journal of Climate ◽

10.1175/jcli-d-16-0138.1 ◽

2016 ◽

Vol 29 (20) ◽

pp. 7507-7527 ◽

Cited By ~ 20

Author(s):

Oluwayemi A. Garuba ◽

Barry A. Klinger

Keyword(s):

Heat Flux ◽

Heat Input ◽

Surface Heat Flux ◽

Heat Content ◽

Surface Heat ◽

Global Ocean ◽

Passive Component ◽

Ocean Heat Uptake ◽

Anomalous Surface ◽

Heat Uptake

Abstract Global warming induces ocean circulation changes that not only can redistribute ocean reservoir temperature stratification but also change the total heat content anomaly of the ocean. Here all consequences of this process are referred to collectively as “redistribution.” Previous model studies of redistributive effects could not measure the net global contribution to the amount of ocean heat uptake by redistribution. In this study, a global ocean model experiment with abrupt increase in surface temperature is conducted with a new passive tracer formulation. This separates ocean heat uptake into contributions due to redistribution temperature and surface heat flux anomalies and those due to the passive advection and mixing of surface heat flux anomalies forced in the atmosphere. For a decline in the Atlantic meridional overturning circulation of about 40%, redistribution nearly doubles the Atlantic passive anomalous surface heat input and depth penetration of temperature anomalies. However, smaller increases in the Indian and Pacific Oceans cause the net global redistributive contribution to be only 25% of the passive contribution. Despite the much larger anomalous surface heat input in the Atlantic, the Pacific gains heat content anomaly similar to that in the Atlantic because of export from the Atlantic and Indian Oceans via the global conveyor belt. Of this interbasin heat transport, most of the passive component comes from the Indian Ocean and the redistributive component comes from the Atlantic.

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The Role of WISHE in Secondary Eyewall Formation

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-17-0236.1 ◽

2018 ◽

Vol 75 (11) ◽

pp. 3823-3841 ◽

Cited By ~ 6

Author(s):

Chieh-Jen Cheng ◽

Chun-Chieh Wu

Keyword(s):

Control Experiment ◽

Inner Core ◽

Surface Wind ◽

Surface Heat ◽

Heat Fluxes ◽

Surface Heat Fluxes ◽

Secondary Eyewall Formation ◽

Tangential Wind ◽

The Impact

Abstract Numerical simulations are conducted to examine the role of the wind-induced surface heat exchange (WISHE) mechanism in secondary eyewall formation (SEF). The control experiment exhibits a coherent secondary eyewall structure as quantified by various parameters (e.g., the azimuthal-mean tangential wind and vertical velocity). Prior to SEF, an area characterized by increasing diabatic heating, enhanced inertial stability, and increasing supergradient winds at the top of the boundary layer is observed outside the eyewall. While these characteristics offer the possibility of both balanced and unbalanced dynamical pathways to SEF, the focus of this study is to evaluate the impact of WISHE. To examine the sensitivity of SEF to WISHE, the surface wind used for the calculation of surface heat fluxes is capped at several designated values and at different radial intervals. When the heat fluxes are moderately suppressed around and outside the SEF region observed in the control experiment, sensitivity experiments show that the formation of the outer eyewall is delayed, and the intensity of both eyewalls is weaker. When the heat fluxes are strongly suppressed in the same region, SEF does not occur. In contrast, suppressing the surface heat fluxes in the storm’s inner-core region has limited effect on the evolution of the outer eyewall. This study provides important physical insight into SEF, indicating that WISHE plays a crucial role in SEF and tropical cyclone evolution.

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