A Laboratory Study of the Effect of Surface Waves on Heat and Momentum Transfer at High Wind Speeds

Abstract

This paper describes laboratory experiments (using a high‐speed wind‐wave flume) of the effects of water waves on heat and momentum exchange in the near‐water atmospheric boundary layer at high wind speeds. Different from previous experiments of this type, the parameters of waves were controlled by a net stretched along the entire channel to effectively decrease the fetch. This helped to achieve dependency of the transfer coefficients on two independent parameters, namely, the wind speed and fetch (expressed via variations of the wavefield). Another key to the experiment was using a stable temperature stratification of the air flow, with the temperature of the air entering the flume 15–25° higher than the water. The experiments showed a sharp increase in the heat exchange coefficient at winds exceeding 33–35 m/s, similar to that observed earlier in the high‐speed wind‐wave flume of Kyoto University with conditions of unstable temperature stratification of the air flow. The joint analysis of the data obtained in the high‐speed wind‐wave flumes of IAP RAS and Kyoto University yields the universal dependency of the exchange coefficients and the temperature roughness on the peak wave number of surface wave spectra. This is independent of the type of temperature stratification of the atmospheric boundary layer, either stable or unstable. The sharp increase in the heat exchange coefficient is shown to be associated with increased whitecapping.

Air–Sea Enthalpy and Momentum Exchange Coefficients from GPS Dropsonde Measurements in Hurricane Conditions

“…It should also be emphasized that the growth in the dependence of the enthalpy exchange coefficient on wind speed is significantly weaker than that observed in the laboratory experiments reported in [38,42]. This result needs further study and may be associated with the different features of laboratory and field conditions.…”

“…In this paper, we propose the application of a modified profiling method based on the use of data not from the region of constant fluxes but from the wake part. We applied this method (in earlier work) to the results of laboratory modeling [18,38], and the method was used further to retrieve dynamic parameters in tropical cyclones [34]. In the present study, we have expanded the dataset (including the consideration of the data from CBLAST), and, in addition, we modified the profiling method to retrieve the thermodynamic parameters (Section 4).…”

“…Nevertheless, the observed effect requires further investigation. The fact that CK does not demonstrate significant changes in major hurricane conditions may be due to an increase in the number of wave-breaking events and the associated whitecapping; both of these phenomena lead to opposing effects-the effect of reducing aerodynamic drag due to the sea surface whitecap masking and the growth in temperature roughness due to sea-surface-area increase and the intensification of mixing, causing water surface renewal due to whitecapping (see [38]). .…”

“…This result needs further study and may be associated with the different features of laboratory and field conditions. In particular, it may be related to the decreasing dependence of the exchange coefficients on the wave fetch (or the wave age parameter), which differs dramatically in laboratory and field conditions [38].…”

Surface Layer Drag Coefficient at Different Radius Ranges in Tropical Cyclones

“…Bi et al [14] used offshore tower observation and found C d peaked at 18 m s −1 and decreased afterward, but leveled off when larger than 27 m s −1 . Other studies with various methods generally also found the same feature that C d decreased or leveled off with wind speed when it was larger than around 30 m s −1 (e.g., [15][16][17][18][19][20][21][22][23][24]).…”