Applicability of Micrometeorological Transfer Coefficient to Estimate the Long-period Means of Fluxes in the Air-sea Interface

Abstract

It is shown that the long-period means of the transfers of momentum, sensible heat and water vapor in the air-sea interface may be expressed by several terms. The first term is the same expression as the so-called bulk formula making use of the transfer coefficient known from the micrometeorological observations. The other terms consist of the wind velocity variance, of the covariances between the wind velocity and sea-air temperature difference and between the wind velocity and sea-air water vapor pressure difference, and of the third-order correlation between the wind velocity, temperature and water vapor differences. A statistical analysis was made for the data of wind, temperature and water vapor pressure obtained by twelve weather ships in the Pacific and Atlantic Oceans.And it is concluded that the time averaged quantities of the sensible and the latent heat transfers for the periods shorter than one day may be approximately calculated by the bulk formula using the time averaged values for the same period of the wind velocity and of the sea-air temperature and water vapor differences.On a certain occasion, however, for a period longer than few days the difference between the true heat transfer and the approximate value from calculation may become significant.

Heat Balance of the East China Sea during the Air Mass Transformation Experiment

“…(The geostrophic wind speed was obtained from the pressure gradients over a distance of order 200-300km. See Kondo, 1977.) From this figure we can find the apparent roughness length of the land station as z0' = 0.5cm for Okinawa and z0' =2cm for Miyakojima. (It is naturally said that this value does not mean the roughness value in an ordinary sense.)…”

“…In that case the daily means were used for the following meteorologic parameters: wind speed, air temperature and vapor presure. The errors in the fluxes obtained by use of these parameters, which were averaged over long intervals of time, are of essentially negligible magnitude, provided that the time intervals over which the meteorologic data were averaged were no more than one day or so (Kondo, 1972;Jobson, 1972). Fig.…”

“…The turbulent transports of heat (H and lE) and momentum (*) at the sea surface were estimated by use of the aerodynamic bulk coefficients under diabatic conditions (Kondo, 1975). In that case the daily means were used for the following meteorologic parameters: wind speed, air temperature and vapor presure.…”

“…2 indicates the relationship of u10/G versus G in neutral stabilities, which can be obtained from the relationship between u* and zo (Kondo, 1975) in combination with the Planetary Boundary Layer model for the wind profile (e.g., Blackadar, 1962), where u* is the friction velocity, and zo the aerodynamic roughness length of the sea surface. In addition to the latter relationship, the atmospheric stability was taken into account for practical calculations (see Kondo, 1977).…”

“…One of these aims is to evaluate the heat transfer from the sea surface into the air, especially in areas where the air-mass transformation is active. In the preparatory research for this purpose, Kondo (1975) developed an aerodynamic bulk technique which can be applied to evaluating the turbulent fluxes in the diabatic atmosphere such as that over the AMTEX sea areas.…”