For the purpose of the continuous measurement of the total rate of ion formation in the atmosphere, a device was developed which consisted of five identical ionization chamber units. Ionization was measured by using three sets of apparatus, two of which were composed of two chamber units in order to compensate the residual ionization of the chamber, and the rest was a single chamber unit. For obtaining the working characteristics of newly constructed apparatus, long-dated observations on the some fields were done. The newly constructed apparatus can give continuous recording, fairly accurate evaluation of the total rate of ion formation and its diurnal variation in the atmosphere.
When the aerosols originated on land are dispersed over the ocean, they are not only decreased in the concentration, but deformed in the pattern of size distribution. This deforma-tion was ascertained by the experiments aboard an observation ship in 1972 and 1974. Based on the mobility spectrometry of atmospheric ions using the apparata we have developed, and the concurrent size spectrometry of large particles using a Royco Optical Counter, the whole size distribution of aerosol particles covering the radius range from 3 nm to 4μm was determined over the cruising course of 1000 km from Tokyo. With the aid of the result of 222Rn concentration measurements, the effect of dilution associated with the spatial dispersion was estimated. Subtracting the dilution factor from the apparent decay rate of the aerosol concentration, the residence time of aerosols was determined in relation to the particle size. In both the expeditions in 1972 and 1974, the deformation of the size distribution was found to take place in such a way that the center of gravity of the distribution was shifted towards smaller size with the increasing age of aerosols.
A study has been made of the aggregation of ice crystals of typical dimension 50μm. which interacted while falling freely in an electric field. Aggregation was increased by up to 30% in an electric field of the order of 105Vm-1 and the aggregation was found to be temperature depend- ent with the electric field having a maximum effect at -8°C.
Huge band echoes of 200 to 400km in width have been frequently observed by Mt. Fuji radar or by multi-radar echo composite. These band echoes are considered mesoscale system in the direction normal to them. The orientations of the band echoes are nearly WSW to ENE. The mesoscale meteorological structure associated with the band echoes is examined with routine radiosonde data. In order to extract the features common and essential to the band echo, the mean structure of various meteorological elements is prepared by superposing a large number of the cases. The following features are obtained from the mean vertical cross-section across the band echo. (1) Within the band echo of stratiform type, a slanting layer with large horizontal gradient of wet-bulb potential temperature (θw) is found in the lower and middle troposphere. Along this slanting layer, the vertical vorticity takes large values. The inclination of the layer is ca. 1/100, which is reasonable value for usual frontal surface. (2) Above this front-like layer, the updraft is found, the maximum value of which is several tens mb/hr and is located on the southside of the center line of band in the middle troposphere. In conformity with this, the intense echo zone is found also on the south of the center line. Below the front-like layer, the downdraft is present. (3) In the vertical cross-section of wind component parallel to the orientation of band echo, jet-like strong wind is situated in the central region of band echo at ca. 500mb, and extends slantwise toward lower levels to reach 700mb near the southern edge of band echo. (4) In the case of convective band echo, the front-like layer as seen from the distributions of θw and vertical vorticity is situated on the northside of the band echo, and the band echo seems to develop over the tongue of high θw in the lower troposphere. That is, the convective band echo is considered prefrontal in nature. (5) In the case of convective type, the wind component parallel to the band echo is fairly small, compared with the case of stratiform type. The above features will serve for understanding the mechanism of band echo and also for estimating the mesoscale meteorological field from the observed radar echo pattern in the data sparse area.
Vertical conditions on 248 days during two summer seasons are investigated to study the distinctive characteristics of the stratification on days with thunderstorms in the northern Kanto plain. For the sake of convenience atmosphere is divided into two layers, upper layer and lower layer. It is recognized that high degree of conditional instability of an upper layer is not the sufficient condition for the occurrence of thunderstorms. However, there are distinct differences of vertical stabilities of a lower layer between on days with thunderstorms and on days without a thunder-storm when an upper layer is conditionally unstable. Namely, it is shown that vertical movement of an air parcel in a lower layer on the former is easier than on the latter. It is also shown that the ratio of the degree of conditional instability of an upper layer to the degree of stability of a lower layer is an important factor affecting the occurrence of thunderstorms rather than their values. These conditions are interpreted into suggesting an interaction between a convective cloud and its subcloud layer, and an instability index is obtained by assuming the interaction. It is shown that this instability index has higher association with the occurrence of thunderstorms than Showalter stability index has. Therefore, the stronger relation is suggested between the occur-rence of thunderstorms and the stability of the whole atmosphere than it has been pointed out.
Vertical fluxes of momentum, sensible heat and water vapour were determined during the 1974 Air Mass Transformation Experiment at 3 sites using the eddy correlation and spectral density techniques. The paper describes these fluxes in terms of the bulk transfer coefficients during the cold air outbreak occurring between February 23rd and 28th. The evidence suggests an increase of the neutral drag coefficient (referred to 10m) with wind speed, to a value of 2×10-3 for wind speed approaching 15m s-1, whilst the ‘neutral’ heat and w.v. transfer coefficients remain approximately constant at 1.5×10.3 over the wind speed range 4-15m s-1. The mean sensible and latent heat fluxes for this 5 day period, based on data from Tarama-jima and Miyakojima were 11 mw cm-2 and 55 mw cm-2 (226 langleys day-1 and 1130 langleys day-1) respectively. The implied Bowen ratio of 0.20 is consistent with the measured sea surface temperature of 21°C, in agreement with the work of Priestley and Taylor (1972).
The diffuse reflection radiation from an inhomogeneous plane-parallel planetary atmosphere including ozone and aerosols is computed by using the “adding” method (Takashima, 1974) at wavelengths 0.30μ, 0.32μ and 0.34μ. Deirmendjian modified Gamma function is adopted for their aerosol size distribution (Deirmendjian, 1969). The values of optical thicknesses of atmospheric compositions and vertical distributions are given by Elterman (1968). Computational results show that (1) at λ=0.30μ, where absorption due to Ozone is predominant, intensity of the upwelling radiation increases at most 10 percent in the presence of aerosols when the nadir angle of measurements is within about 60 degrees. (2) At λ=0.34μ, where absorption due to ozone is negligible, it increases up to about 20 percent. In general intensity ratio increases in the presence of aerosols more at λ=0.34μ than at λ=0.30μ, in comparison with that of Rayleigh and ozone mixed atmosphere. (3) The values of the diffusely reflected radiation in terms of aerosols of refractive index m=1.50 is higher than that of 1.35.