Papers on how longwave radiation warms oceans

The Impact of Wind Gusts on the Ocean Thermal Skin Layer – Zappa et al. (2019) “The thermodynamic and emissive properties of the ocean thermal skin layer are crucial contributors to air‐sea heat flux. In order to properly observe ocean surface temperature without disturbing any delicate fluid mechanical processes, thermal infrared imaging is often used. However, wind impacting the ocean surface complicates the extraction of meaningful information from thermal imagery; this is especially true for transient forcing phenomena such as wind gusts. Here, we describe wind gust‐water surface interaction through its impact on skin layer thermal and emissive properties. Two key physical processes are identified: (1) the growth of centimeter‐scale wind waves, which increases interfacial emissivity, and (2) microscale wave breaking and shear, which mix the cool skin layer with warmer millimeter‐depth water and increase the skin temperature. As more observations are made of air‐sea interaction under transient forcing, the full consideration of these processes becomes increasingly important.” Zappa, C. J., Laxague, N. J. M., Brumer, S. E., & Anderson, S. P. (2019). The impact of wind gusts on the ocean thermal skin layer. Geophysical Research Letters, 46, 11301– 11309. https://doi.org/10.1029/2019GL083687. [FULL TEXT]

The Response of the Ocean Thermal Skin Layer to Variations in Incident Infrared Radiation – Wong & Minnett (2018) “Ocean warming trends are observed and coincide with the increase in concentrations of greenhouse gases in the atmosphere resulting from human activities. At the ocean surface, most of the incoming infrared (IR) radiation is absorbed within the top micrometers of the ocean’s surface where the thermal skin layer (TSL) exists. Thus, the incident IR radiation does not directly heat the upper few meters of the ocean. This paper investigates the physical mechanism between the absorption of IR radiation and its effect on heat transfer at the air‐sea boundary. The hypothesis is that given the heat lost through the air‐sea interface is controlled by the TSL, the TSL adjusts in response to variations in incident IR radiation to maintain the surface heat loss. This modulates the flow of heat from below and hence controls upper ocean heat content. This hypothesis is tested using the increase in incoming longwave radiation from clouds and analyzing vertical temperature profiles in the TSL retrieved from sea‐surface emission spectra. The additional energy from the absorption of increasing IR radiation adjusts the curvature of the TSL such that the upward conduction of heat from the bulk of the ocean into the TSL is reduced. The additional energy absorbed within the TSL supports more of the surface heat loss. Thus, more heat beneath the TSL is retained leading to the observed increase in upper ocean heat content.” Wong, E. W., & Minnett, P. J. (2018). The response of the ocean thermal skin layer to variations in incident infrared radiation. Journal of Geophysical Research: Oceans, 123, 2475‐ 2493. https://doi.org/10.1002/2017JC013351. [FULL TEXT]

Bulk Parameterization of Air-Sea Exchanges of Heat and Water Vapor Including the Molecular Constraints at the Interface – Liu et al. (1979) “A model is developed for the marine atmospheric surface layer including the interfacial sublayers on both sides of the air-sea interface where molecular constraints on transports are important. Flux-profile relations which are based on the postulation of intermittent renewal of the surface fluid aye matched to the logarithmic profiles and compared with both field and laboratory measurements. These relations enable numerical determination of air-sea exchanges of momentum, heat and water vapor (or bulk transfer coefficients) employing the bulk parameters of mean wind speed, temperature and humidity at a certain height in the atmospheric surface layer, and the water temperature. With increasing wind speed, the flow goes from smooth to rough and the bulk transfer coefficient for momentum also increases. The increase in roughness is associated with increasing wave height which in the present model results in sheltering at the wave troughs. Due to the decrease in turbulent transports, the transfer coefficients of heat and water vapor decrease slightly with wind speed after the wind speed exceeds a certain value. The bulk transfer coefficients are also found to decrease with increasing stability. If the “bucket temperature” which typically gives the water temperature a few centimeters below the surface is used, rather than the interfacial temperature, erroneous results may be obtained when the air-sea temperature difference is small. By including the effects of stability and interfacial conditions in bulk parameterization, the model provides a way to account for physical conditions which are known to affect air-sea exchanges.” Liu, W. T., Katsaros, K. B., & Businger, J. A. (1979). Bulk Parameterization of Air-Sea Exchanges of Heat and Water Vapor Including the Molecular Constraints at the Interface, Journal of Atmospheric Sciences, 36(9), 1722-1735. https://doi.org/10.1175/1520-0469(1979)036<1722:BPOASE>2.0.CO;2. [FULL TEXT]

Heat thermal structure in the interfacial boundary layer measured in an open tank of water in turbulent free convection – Katsaros et al. (1977) “The thermal structure in the boundary layer and its relation to the heat flux from the cooling and evaporating surface of a deep tank of water are investigated. When a deep layer of water in contact with still air above loses heat to the air, the cooled water in a region just under the surface converges along lines and then plunges down in sheets. These sheets of falling water dissipate as they move into the body of the water, which is in turbulent motion. The vertical profiles of the horizontally averaged temperature and its standard deviation agree fairly closely with theoretical profiles based on time averages of the solution to the heat diffusion equation. The differences between observed and thus predicted profile shapes are consistent with the expected effects of the falling cold thermals and the warm return flow, which are neglected in the theories. The profiles of the standard deviation have large values up to the interface and lie between predictions based on boundary conditions of constant surface temperature and constant heat flux, in keeping with the experimental conditions. The relation between the net heat flux and the temperature difference across the boundary layer is given in non-dimensional form by N = 0[sdot ]156R^{0[sdot ]33}, which is in good agreement with the asymptotic similarity prediction N [vprop ] R1/3 but lower than theoretical calculations of the upper bound of N vs. R.” Katsaros, K., Liu, W., Businger, J., & Tillman, J. (1977). Heat thermal structure in the interfacial boundary layer measured in an open tank of water in turbulent free convection. Journal of Fluid Mechanics, 83(2), 311-335. doi:10.1017/S0022112077001219. [FULL TEXT]

Air-sea bulk transfer coefficients in diabatic conditions – Kondo (1975) “On the basis of recent data for the roughness Reynolds number of the sea surface, and using the Owen-Thomson theory on the transfers of heat and mass between a rough surface and the flow above it, the bulk transfer coefficients of the sea surface have been estimated. For a reference height of 10 m, the neutral-lapse transfer coefficient for water vapor is larger by only a few percent than that for sensible heat. When the wind speed at the 10-m height is u ₁₀>3 m s⁻¹, the coefficient for sensible heat C _H is larger by about 10% than that for momentum C _D . For u ₁₀<5 m s⁻¹, however, the value of C _D exceeds the value of C _H , and for u ₁₀=15 m s⁻¹ it is shown that C _H ≈0.8C _D . It may be also proposed that 10³ C _D =1.11 to 1.70, 10³ C _E =1.18 to 1.30, and 10³ C _H =1.15 to 1.26 for a range of u ₁₀=4 to 20 m s⁻¹. A plot of diabatic transfer coefficients versus wind speed is obtained by using a parameter of the sea-air temperature difference. For practical purposes, the coefficients are approximated by empirical formulae.” Kondo, J. Air-sea bulk transfer coefficients in diabatic conditions. Boundary-Layer Meteorol 9, 91–112 (1975). https://doi.org/10.1007/BF00232256.