Papers in Meteorology and Geophysics

For the evaluation of vertical turbule n t fluxes over wide areas such as oceans, it is difficult to measure three dimensional turbulent fluctuations, mean vertical profiles of wind speed, potential air temperature and humidity over the whole area in question.
Accordingly, for practical purposes a simple and more convenient evaluat i ng method should be developed.
In this paper, such a method is developed by use of flux-profile relationship.
For obtaining solutions, simultaneous transcendental equations ar e solved by an iterative method. The following properties of turbulent fluxes are studied in this paper:
(1) Estimation of mean roughness height by our bulk method shows good agreem e nt with the one by the extrapolation method of lower profiles of mean wind velocities under the best neutral condition. And also it is found that there exists an optimum choice of measurement levels to make errors of estimated Z0 minimum.
(2) The fluxes of sensible heat and momentum a gree relatively well with the ones obtained by direct measurement, but as latent heat fluxes become larger, the values obtained by the bulk method tend to be larger than the directly measured ones.
(3) The fluxes of momentum, sensible heat and latent heat obtained by our bulk method over the sea agree very well with ones obtained by Kondo's bulk formulae.
(4) Diurnal variation of sensible heat flux obtained by our method sh o ws good correspondence with that of net radiation and cloud amounts.
(5) Momentum fluxes calculated by our bul k method vary a little with the two measurement levels except under stable condition. And relative errors of estimated fluxes to the directly measured average fluxes are 30% to 50% about in the middle levels of profiles, except near neutral condition. On the other hand, the variations of sensible heat fluxes with the two measurement levels are relatively small under diabetic condition and relative errors of them are also minimum in the middle of profiles.

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When the stable air mass over the sea comes in over the land heated by insolation, an internal boundary layer tends to be created by the difference of the surface temperatures and surface roughness between the land and the sea. At the same time, if there is a pollutant source near the seashore, fumigation may occur. This study aim at making clear the characteristics of this fumigation. For this purpose, two steps of numerical simulation are put into practice. In the first step, wind and diffusivity profiles in the internal boundary layer are calculated from the numerical model by the use of equations of the surface boundary layer based on the mixing length theory (eq.1-11). Secondly, using the result of the first step, the concentration of the pollutant emitted from the point source is calculated from the advection and diffusion model (eq.12). Since this study is based upon surface boundary layer equations, the result is not applicable to the larger scale phenomena.
The resul t s of the simulations are as follows
( 1 ) When only the surface roughness of the land is different from that of the sea surface in neutral condition, fumigation dose not clearly occur (See Fig.4).
( 2 ) Even if the stability condition over the sea is good and the surface temperatures of the land and the sea have different values, fumigation does not always occuer. Maximum surface concentration is largest at a certain combination of stability length at the sea Lo, and surface temperature difference 4T; for example, with the effective stack height h=52.5 m, and L0=50 m, the maximum surface concentration is largest when 4T is about 2°C. But in case ZIT is larger or smaller than 2°C, the maximum surface concentration is low, and the fumigation is not so clear (See Fig.13, Fig.15).
( 3 ) When the effective stack height is low (eq. h=22.5), fumigation tends to occur especially at smaller ziT for the same stability (See Fig.17).
(4) The distribution of concentration from, a constant source is strongly affected by L0,4T and wind velocity U h, at the effective stack height. But the surface roughness length of the land and the sea, z00 and z01, are not so dominant parameters (See Fig.16).

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