The radiative equilibrium and the radiative-convective equilibrium of the Venusian atmosphere corresponding to the averaged insolation are numerically calculated for the layer up to 76km. The non-grey absorption in infra-red region due to carbon dioxide and water vapour and the grey absorption due to the cloud are included in the present study. The amount of solar radiation reaching the ground is assumed to be 1.5% of the solar constant at the orbit of Venus based on the information by Venera-8, and the rest of the absorbed energy is assumed to be distributed uniformly in the cloud layer. The heat trans-port by convection is included by means of eddy mixing of the potential temperature. The results of the present calculations on the radiative equilibrium and the radiative- convective equilibrium lead to the conclusion that the high surface temperature can be explained in terms of a green house effect provided that the concentration of water vapour assumed in the present study is not far from the correct value. Namely, water vapour is indispensable to the maintenance of the high surface temperature. The cloud also has an important effect concerning the infra-red region on the thermal structure of the atmosphere, especially on that in the upper layer. However the cloud's contribution to green house effect seems not to be indispensable, as indicated from the result that the high surface temperature can be maintained in spite of a small optical thickness of the cloud assumed in the present study. In the calculations of the radiative-convective equilibrium, convection takes place in most part of the atmosphere. The eddy diffusion coefficient is of the order of 106cm2/sec in the lower layer and 107cm2/sec in the upper layer. However a non-convective layer appears below the cloud base under most conditions assumed in the present study. It suggests that a connection between the lower layer and the cloud layer is rather weak. A calculation on the diurnal variation of the Venusian atmosphere was made by the present model in which lateral mixing is neglected. The result indicates that in the night side strong convection occurs to transport heat upward within the cloud layer and prevents cooling of the cloud top. The maximum diurnal temperature range averaged over a layer between the surface and the 1km level turns out to be 0.3°K.
During AMTEX 1974, the 50m tower on Tarama Island reported a strong diurnal cycle in the eddy fluxes of sensible and latent heat at 50m height even for land fetches as short as 1km. A numerical assessment is made demonstrating that the large aerodynamic roughness of the island, combined with unstable stratification in the lower atmosphere enables significant fractions of the land fluxes to be transported through the 50m level. On an energy basis, however, it is difficult to account for the high values of the fluxes observed.
The results of fluctuation measurements of wind velocity and air temperature above the ocean surface at the marine observation tower are presented. And vertical fluxes of momentum and sensible heat obtained from the eddy correlation method are shown with various statistical quantities of turbulence. Intensities of turbulence are estimated to the values of σu/u=0.089, σv/u=0.060, σw/u=0.044 respectively at about 6.4m high for neutral conditions of atmosphere. The drag co-efficient CD of momentum transfer is approximated by the expression 103CD=0.36+0.118u10 for 3<u10<8m/s and 1.01+0.036u10 for 8<u10<15m/s. Similary the heat flux co- efficient CH is 103CH=1.1 for u10>4m/s and this coefficient is scattered in weak winds. Spectra and cospectra of turbulence are analyzed and these curves are classified into a few types according to the stability parameter z/L. In addition, it is shown from the simultaneous measurement of wind velocity and sea surface displacement that the coherence between wind and wave is too small to be recognized in moderate winds at the level of 6m height.
This paper deals with turbulent properties of vertical velocities and wind inclinations at height of 40m in strong winds. In the wind of sea trajectory, the intensity of turbulence was mostly in the range from 0.03-0.04. The ratio of vertical velocity to longitudinal one, that of vertical velocity to friction velocity, and non-dimensional frequency _??_m at which logarithmic power spectrum had a maximum were in good agreement with those by other investigators. The lateral correlation was small compared with that of longitudinal velocities. It vanished almost at the separation of 35m. When the square root of coherence was ex-pressed by an exponential function, the decay parameter scattered in a wide range but it was estimated from 14-16 on the average. The effect of averaging on peak values and scales of wind inclinations was discussed as engineering application. With increase of averaging time, peak values decreased and lateral scales increased, but the rate of increase was small compared with that of decrease of the peak values.
To investigate the temperature dependency of the angle between the c-axes of neighbour-ing crystals of frozen water droplets, supercooled water droplets of 0.6 to 1.0mm in diameter were nucleated and frozen using single crystal frost ice in temperature ranges of -10 to -15°C, -15 to -20°C and -20 to -25°C. At the range of -15 to -20°C, the peak of the angles between the c-axes of neighbouring crystals was around 20°, on the other hand, there were two peaks around 20° and 70° at the temperature range of -20 to -25°C.The peak around 20°C obtained in the previous paper by authors (1976a) in the temperature range of -17 and -23°C is considered to be affected by relatively warmer temperatures above -20°C. The peak around 70°C appeared at the temperature range of -20 to -25°C in this experiment, strictly coincided with the results of observations in natural snow crystals grown at air temperatures below -20°C. At the temperature range of -10 to -15°C, almost all supercooled water droplets froze single crystals and the orientation of the c-axis of the frozen crystals was the same as that of the seed single crystal frost ice. The directions of protrusions which appeared when the supercooled water droplets were incidently frozen were in parallel to the c-axis of seed crystal. The reason why the orientation of the c-axis of frozen water droplets and the direction of protrusions coincided with the direction of the c-axis of seed crystals were considered. And further, the course of the freezing process of the supercooled water droplets nucleated and frozen by contact with a single crystal frost ice was taken by a motordriven camera mounted on a polarizing microscope.
The effect of the radiosonde suspension length on temperature measurement has been surveyed by comparing day-night temperature differences. The comparisons were made at 6 upper-air standard levels at 10 stations in Japan for two 4-year periods of 1964-67 and 1969-72 except 1968 when the suspension length for the Japanese routine radiosondes was changed from 7m to 15m. It is found that the day-night temperature differences in and after 1969 are considerably reduced in contrast to the differences in and before 1967.