Search Results
You are looking at 1 - 7 of 7 items for :
- Author or Editor: S. A. Hsu x
- Journal of Physical Oceanography x
- Refine by Access: All Content x
Abstract
A mechanism is proposed for a physical explanation of the increase in wind stress (drag) coefficient with wind speed over water surfaces. The formula explicitly incorporates the contribution of both winds and waves through the parameterizations of an aerodynamic roughness equation. The formula is consistent with measurements from the field and with results obtained by numerical models for storm surges and water level fluctuations.
Abstract
A mechanism is proposed for a physical explanation of the increase in wind stress (drag) coefficient with wind speed over water surfaces. The formula explicitly incorporates the contribution of both winds and waves through the parameterizations of an aerodynamic roughness equation. The formula is consistent with measurements from the field and with results obtained by numerical models for storm surges and water level fluctuations.
Abstract
A formula that linearly relates the difference in wind speed between onshore and offshore regions, as tested successfully in the Great Lakes region, has been revised and extended to other parts of the world. This formula is further substantiated theoretically by using an approximation of the equations of motion. Contribution of air–sea temperature difference to wind speed and direction, as well as the meteorological conditions under which this formula way be applied, are also evaluated.
Abstract
A formula that linearly relates the difference in wind speed between onshore and offshore regions, as tested successfully in the Great Lakes region, has been revised and extended to other parts of the world. This formula is further substantiated theoretically by using an approximation of the equations of motion. Contribution of air–sea temperature difference to wind speed and direction, as well as the meteorological conditions under which this formula way be applied, are also evaluated.
Abstract
No abstract available.
Abstract
No abstract available.
Abstract
At the air–sea interface, estimates of evaporation or latent heat flux and the Monin–Obukhov stability parameter require the measurements of dewpoint (T dew) or wet-bulb temperature, which are not routinely available as compared to those of air (T air) and sea surface temperature (T sea). On the basis of thermodynamic considerations, this paper first postulates that the quantity of (q sea − q air) for the difference in specific humidity between the sea surface and its overlying air is related to the quantity of (T sea − T air). Using hourly measurements of all three temperatures, that is, T sea, T air, and T dew from a buoy in the Gulf of Mexico under a severe cold air outbreak, a linear correlation between (q sea − q air) and (T sea − T air) does exist with a compelling high correlation coefficient, r, of 0.98 between these two quantities. Second, based on this Clausius-Clapeyron effect, the Bowen ratio B is proposed to relate to the quantity of (T sea − T air) only such that B = a(T sea − T air) b . Using all data for these three temperatures available from four stations in the Gulf from 1993 through 1997 reveal that for deepwater a varies from 0.077 to 0.078, b from 0.67 to 0.71, and r from 0.85 to 0.89. Similar equations for the nearshore region are also provided. Limited datasets from the open ocean also support this generic relationship between B and the quantity of (T sea − T air).
Abstract
At the air–sea interface, estimates of evaporation or latent heat flux and the Monin–Obukhov stability parameter require the measurements of dewpoint (T dew) or wet-bulb temperature, which are not routinely available as compared to those of air (T air) and sea surface temperature (T sea). On the basis of thermodynamic considerations, this paper first postulates that the quantity of (q sea − q air) for the difference in specific humidity between the sea surface and its overlying air is related to the quantity of (T sea − T air). Using hourly measurements of all three temperatures, that is, T sea, T air, and T dew from a buoy in the Gulf of Mexico under a severe cold air outbreak, a linear correlation between (q sea − q air) and (T sea − T air) does exist with a compelling high correlation coefficient, r, of 0.98 between these two quantities. Second, based on this Clausius-Clapeyron effect, the Bowen ratio B is proposed to relate to the quantity of (T sea − T air) only such that B = a(T sea − T air) b . Using all data for these three temperatures available from four stations in the Gulf from 1993 through 1997 reveal that for deepwater a varies from 0.077 to 0.078, b from 0.67 to 0.71, and r from 0.85 to 0.89. Similar equations for the nearshore region are also provided. Limited datasets from the open ocean also support this generic relationship between B and the quantity of (T sea − T air).
Abstract
A dynamic roughness equation including major wind and wave interaction parameters (wind shear velocity, wave height, and phase velocity) is derived. Because this equation implicitly incorporates the effects of wave steepness, relative water depth, and wind duration and fetch, it may be applied to a wide variety of natural conditions. This equation was used to construct a nomogram which can be utilized to determine the wind stress at the sea surface, given phase velocities, wave heights, and the wind speed at any height in the atmospheric boundary layer. The proposed relationships are verified by the available field and laboratory data under near-neutral atmospheric stability conditions from which the appropriate parameters could be determined.
Abstract
A dynamic roughness equation including major wind and wave interaction parameters (wind shear velocity, wave height, and phase velocity) is derived. Because this equation implicitly incorporates the effects of wave steepness, relative water depth, and wind duration and fetch, it may be applied to a wide variety of natural conditions. This equation was used to construct a nomogram which can be utilized to determine the wind stress at the sea surface, given phase velocities, wave heights, and the wind speed at any height in the atmospheric boundary layer. The proposed relationships are verified by the available field and laboratory data under near-neutral atmospheric stability conditions from which the appropriate parameters could be determined.
Abstract
Studies suggested that neutral-stability wind speed at 10 m U 10 ≥ 9 m s −1 and wave steepness H s /L p ≥ 0.020 can be taken as criteria for aerodynamically rough ocean surface and the onset of a wind sea, respectively; here, H s is the significant wave height, and L p is the peak wavelength. Based on these criteria, it is found that, for the growing wind seas when the wave steepness increases with time during Hurricane Matthew in 2016 before the arrival of its center, the dimensionless significant wave height and peak period is approximately linearly related, resulting in U 10 = 35H s /T p ; here, T p is the dominant or peak wave period. This proposed wind–wave relation for aerodynamically rough flow over the wind seas is further verified under Hurricane Ivan and North Sea storm conditions. However, after the passage of Matthew’s center, when the wave steepness was nearly steady, a power-law relation between the dimensionless wave height and its period prevailed with its exponent equal to 1.86 and a very high correlation coefficient of 0.97.
Abstract
Studies suggested that neutral-stability wind speed at 10 m U 10 ≥ 9 m s −1 and wave steepness H s /L p ≥ 0.020 can be taken as criteria for aerodynamically rough ocean surface and the onset of a wind sea, respectively; here, H s is the significant wave height, and L p is the peak wavelength. Based on these criteria, it is found that, for the growing wind seas when the wave steepness increases with time during Hurricane Matthew in 2016 before the arrival of its center, the dimensionless significant wave height and peak period is approximately linearly related, resulting in U 10 = 35H s /T p ; here, T p is the dominant or peak wave period. This proposed wind–wave relation for aerodynamically rough flow over the wind seas is further verified under Hurricane Ivan and North Sea storm conditions. However, after the passage of Matthew’s center, when the wave steepness was nearly steady, a power-law relation between the dimensionless wave height and its period prevailed with its exponent equal to 1.86 and a very high correlation coefficient of 0.97.
