scholarly journals Variability of Surface Heat Fluxes and Its Driving Forces at Different Time Scales Over a Large Ephemeral Lake in China

2018 ◽  
Vol 123 (10) ◽  
pp. 4939-4957 ◽  
Author(s):  
Xiaosong Zhao ◽  
Yuanbo Liu
Keyword(s):  
Time Scales ◽  
Driving Forces ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Surface Heat Fluxes ◽  
Different Time Scales

The Impact of Rapid Wind Variability upon Air–Sea Thermal Coupling

2008 ◽  
Vol 21 (4) ◽  
pp. 621-637 ◽  
Author(s):  
Philip Sura ◽  
Matthew Newman
Keyword(s):  
Wind Speed ◽  
Time Scales ◽  
Multiplicative Noise ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Thermal Coupling ◽  
Surface Heat Fluxes ◽  
State Dependent ◽  
Ocean Coupling ◽  
The Impact

Abstract The basic effect of extratropical atmosphere–ocean thermal coupling is to enhance the variance of both anomalous sea surface temperatures (SSTs) and air temperatures (AIRT) due to a decreased energy flux between the atmosphere and ocean, called reduced thermal damping. In this paper it is shown that rapidly varying surface winds, through their influence upon the turbulent surface heat fluxes that drive this coupling, act to effectively weaken the coupling and thus partially counteract the reduced thermal damping. In effect, rapid fluctuations in wind speed somewhat insulate the atmosphere and ocean from each other. The nonlinear relationship between the rapidly varying wind speed anomalies and SST and AIRT anomalies results in a rapidly varying component of the surface heat fluxes. The clear separation between the dynamical time scales of the ocean and atmosphere allows this rapidly varying flux to be simply approximated by a stochastic process in which rapidly varying wind speed is represented as Gaussian white noise whose amplitude is modulated by the more slowly evolving thermal anomalies. Such state-dependent (multiplicative) noise can alter the dynamics of atmosphere–ocean coupling because it induces an additional heat flux term, the noise-induced drift, that effectively acts to weaken both coupling and dissipation. Another key implication of the outlined theory is that air–sea coupling includes both deterministic and stochastic components. The theory is tested by examining daily observations during extended winter (November–April) at several ocean weather stations (OWSs). Two important results are found. First, multiplicative noise at OWS P effectively decreases the coupling by about one-third, with about a 10% (20%) decrease in the damping of SST (AIRT). This suggests that multiplicative noise may be responsible for roughly half of the AIRT variability at OWS P on subseasonal time scales. Second, OWS observations reveal that joint probability distribution functions of daily averaged SST and AIRT anomalies are significantly non-Gaussian. It is shown that treating the rapidly varying boundary layer heat fluxes as state-dependent noise can reproduce this observed non-Gaussianity. It is concluded that the effect of state-dependent noise is crucial to understand and model atmosphere–ocean coupling.

A Moist Static Energy Framework for Zonal-Mean Storm-Track Intensity

2018 ◽  
Vol 75 (6) ◽  
pp. 1979-1994 ◽  
Author(s):  
Tiffany A. Shaw ◽  
Pragallva Barpanda ◽  
Aaron Donohoe
Keyword(s):  
Time Scales ◽  
Storm Track ◽  
Longwave Radiation ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Net Energy ◽  
Moist Static Energy ◽  
Ocean Energy ◽  
Surface Heat Fluxes ◽  
Static Energy

Abstract A moist static energy (MSE) framework for zonal-mean storm-track intensity, defined as the extremum of zonal-mean transient eddy MSE flux, is derived and applied across a range of time scales. According to the framework, storm-track intensity can be decomposed into contributions from net energy input [sum of shortwave absorption and surface heat fluxes into the atmosphere minus outgoing longwave radiation (OLR) and atmospheric storage] integrated poleward of the storm-track position and MSE flux by the mean meridional circulation or stationary eddies at the storm-track position. The framework predicts storm-track decay in spring and amplification in fall in response to seasonal insolation. When applied diagnostically the framework shows shortwave absorption and land turbulent surface heat fluxes account for the seasonal evolution of Northern Hemisphere (NH) intensity; however, they are partially compensated by OLR (Planck feedback) and stationary eddy MSE flux. The negligible amplitude of Southern Hemisphere (SH) seasonal intensity is consistent with the compensation of shortwave absorption by OLR and oceanic turbulent surface heat fluxes (ocean energy storage). On interannual time scales, El Niño minus La Niña conditions amplify the NH storm track, consistent with decreased subtropical stationary eddy MSE flux. Finally, on centennial time scales, the CO2 indirect effect (sea surface temperature warming) amplifies the NH summertime storm track whereas the direct effect (increased CO2 over land) weakens it, consistent with opposing turbulent surface heat flux responses over land and ocean.

Trends of land surface heat fluxes on the Tibetan Plateau from 2001 to 2012

2017 ◽  
Vol 37 (14) ◽  
pp. 4757-4767 ◽  
Author(s):  
Cunbo Han ◽  
Yaoming Ma ◽  
Xuelong Chen ◽  
Zhongbo Su
Keyword(s):  
Tibetan Plateau ◽  
Land Surface ◽  
Surface Heat ◽  
Heat Fluxes ◽  
The Tibetan Plateau ◽  
Surface Heat Fluxes ◽  
Land Surface Heat Fluxes

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

2021 ◽  
Vol 149 (5) ◽  
pp. 1517-1534
Author(s):  
Benjamin Jaimes de la Cruz ◽  
Lynn K. Shay ◽  
Joshua B. Wadler ◽  
Johna E. Rudzin
Keyword(s):  
Tropical Cyclone ◽  
Surface Wind ◽  
Heat Content ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Ocean Heat Uptake ◽  
Surface Heat Fluxes ◽  
Heat Uptake ◽  
Moisture Fluxes ◽  
New Perspective

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.

Boundary Surface Heat Fluxes in a Square Enclosure with an Embedded Design Element

2010 ◽  
Vol 24 (4) ◽  
pp. 845-849 ◽  
Author(s):  
M. Ajith ◽  
Ranjan Das ◽  
Ramgopal Uppaluri ◽  
Subhash C. Mishra
Keyword(s):  
Boundary Surface ◽  
Surface Heat ◽  
Heat Fluxes ◽  
Design Element ◽  
Surface Heat Fluxes ◽  
Square Enclosure ◽  
Embedded Design
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