[in Japanese]

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Introducing a modified in t e gral diffusivity whose integral range does not contain the surface values of temperature and water vapour, the bulk aerodynamic method is surveyed by the use of the data obtained on the joint exploration, which was carried out at the Chiba seaport in 1966 by the Meteorological Research Institute, the observational section, JMA and the Meteorological College.
Comparisons of the estimation of H and E du e to the profile method with that due to the bulk method are made and the dependence of the modified integral diffusivity on the stability ratio is also sought. Finally the empirical bulk equations for the estimation of H and E without using the surface values are presented.

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¹⁸O content in cloud droplets is higher in a closed system than in an open system. It is also higher under a non-equilibrium condition than under an equilibrium condition.
In case of the frontal type of precipitation, the observed variation with time in ¹⁸O content agrees fairly well with the calculation using an open model. The change in ¹⁸O content in convective shower which gives snow pellets can be explained by an open model.
The isotopic exchange between falling rain drops an d vapor is more effective in enriching heavier isotopes than evaporation.
The calculated rate constant of isotopic exchange r eaction between falling rain drops and vapor is about half of that given by FRIEDMAN et al. (1962). A smaller amount of isotopic exchange than calculation was observed in rain water.
The relationship b etween D and ¹⁸O contents in precipitation under an equilibrium condition can be expressed as an approximate straight line starting from the original point with a slope less than (αD-1)/(α¹⁸O-1) in the region of slight isotopic fractionation. The deviations from the straight line are ex p lained by the effect of kinetic processes.
The downward shift below the line is due to kinetic evaporation, while the upward shift is due to either the supply of source vapor under a kinetic condition or isotopic exchange between rain drops and vapor which has evaporated under a kinetic condition.
A constant term in Craig's equation for the relation between D and ¹⁸O contents is derived by the fact that ¹⁸O content in source vapor is lower by 1.2% on an average as compared with D content.

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Integrated amounts of ²³⁹Pu during the period from March 1958to the end of 1966 and ²³⁸Pu (from 1959 to 1966) in Tokyo are respectively 0.92 mCi/km2 and 34 uCi/km².²³⁸Pu to ²³⁹Pu ratio from 1959to 1966 is 3.9% which is nearly the same as that in fallout prior to the satellite failure. The mean ratio of ²³⁹Pu/⁹⁰Sr deposition is 1.6%. Assuming 1.6% activity ratio of ²³⁹Pu/⁹⁰Sr, the total release of ²³9Pu and ²³⁸Pu associated with the nuclear test is estimated to be about 0.22 MCi and <10 kCi respectively in this period.
The mean residence time of 239PU is 1.7 years i n both periods from 1959 to 1961 and from 1963 to 1966, which is slightly longer than that of ⁹⁰Sr (1.4 yr.,1963 to 1966).

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In this study, we first investig a t e d the characteristics of areal frequency distribution of heavy rain. Heavy rainfalls were classified by daily precipitation amount as >50mm, >100mm, >150mm, >200mm, >300mm, >400mm,......, and t h e characteristics of areal distribution of these frequencies are expressed. Frequencies of each class of daily precipitation amount from > 0.1mm to > 500mm of the total sum of all stations are of exponential behaviour. The remarkable characteristics of areal distribution are as follows:
( 1 ) The frequency of heavy rain on the east side of peninsulas or islands situated the pacific side is greater than on the west side of them.
( 2 ) In the central part of the Inland Sea, the Sea of Okhotsk coast of Hokkaido and the northern part of the inland area of the Chubu Dis t r i ct, the frequency of heavy rain is considerably low.
( 3 ) High frequency appears along the coast of the Pacific Ocean, especially on the east side of the Izu and the Kii Peninsula, and the i n land area and east coast of the Kyushu District.
From the total annual frequency a n d the seasonal variation of frequency at each station, we can derive four climatic types of heavy rain i n Japan and some transitional ones:
( 1 ) Total frequency is low and heavy rain appears only in the warm season (Hokkaido except the southeast Pacific coast, central part o f the Inland Sea, and parts of the inland area of Honshu).
( 2 ) Total frequency is high and heavy rain appears throughout the year (along the coast of the Pacific Ocean).
( 3 ) Max. of frequency of the year appears in December or very frequent in winter season, but heavy rain more than 100mm appe a rs only in the warm season (along the coast of the Japan Sea).
( 4 ) Total frequency is somewhat high, but heavy rain appears only in the warm season (the inland area of the Kyushu and the northern p a rt of the Kanto Districts).
( 5 ) Example of transitional type: Type ( 1 ) to Type ( 2 ) (the coast of the Bungo and the Kii Channel, the southern part of the inland are a of the Kanto and the Chubu Districts).
The normal of the prec i p itation density (the value obtained by dividing the total sum of precipitation amount by the number of rainy days with a daily precipitation amout of ≥ O.1mm in the same period) is a very suitable index for the frequency of heavy rainfalls, that is, a large value of precipitation density indicated greater frequency of heavy rainfalls.
The ratio of the frequency of heavy rainfalls b e tween a station in level land and an adjacent station in mountain area is 1: 1.4-1.6.
Lastly, it must be noted that the seasonal variation of the s i tuation of Polar Frontal Zone and typhoon or violent cyclone tracks are often responsible for areas of frequent heavy rain.

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Many swarm earthquakes started near Matsushiro from August,1965, and their coda activity still continues as of May,1968. Fig.1 illustrates the daily frequency of perceptible earthquakes, which outlines the present swarm activity.
From examinations of the distribution of initial motions of these earthquakes, activities of magma pockets were inferred as follows. First, the Matsushiro magma pocket started its activity, and later in April,1966, the Wakaho magma pocket became active in addition to the former, and in May,1966, activity of the Oomine magma pocket perticipated in these. Those pockets are believed to have intruded nearly vertically with an incident angle of 5 degrees (see Fig.8).
At the peak of the swarm activity, Mt. Minakami rose or tilted to the north-west. This change was slightly restored later, which probably indicated the end of the main activity. The auther assumes that the deformation of Mt. Minakami is an indication of magma intrusion and that the present swarm is of volcanic nature, which was originated by heat energy from radioactive elements (Th, U, Ra etc. ).

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For the purpose of improving the signal-to-noise ratio of seismological observations of the Japan Meteorological Agency, the attenuation of background noise in a shallow hole has been studied. Three-component seismograph of 1.5 sec in period was placed at depths of 10,20,50,100,150, and 200 m as an observation hole was being bored in the premises of the Meteorological Research Institute, Tokyo. Simultaneous observation was made on the surface by seismograph of the same characteristics, and the comparison between surface and hole was made with respect to frequency and depth (see Figs.1 and 2).
The results are summarized in t he following:
1) Attenuation of background noise is more rapid with higher frequencies (see Figs.5 and 6).
2) Low frequency noises of less than 0.5 cps hardly attenuate with depth (Fig.5). This is also the case with very deep holes of 3000 m t e sted in the United States.
3) As far as observations of local earthquakes with seismograph of 1 sec in period are concerned, significant improvements in signal-to-nois e ratio can be obtained near a depth of 50 m. No improv e m ent of the ratio will probably be expected by any deeper hole, and the optimu m depth both for the signal-to-noise ratio and instrumental op e rations seems to be in this vicinity. Such depth, however, may d e pend to some extent on the geological structure near the surface, and furthe r studies will be made at different places.
4) Short-time noises due to vehicles running near-by or to the dropping weight become insignificant at a depth of 50 m or even less (F ig.8).

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