Fall velocity, mass and cross-sectional area of snowflakes are simultaneously observed in order to obtain the conditional probability function of fall velocity for a given mass. The results are summarized as follow: 1) The frequency histograms of the mass, of the cross-sectional area and of the fall velocity are obtained for 4 snowfalls (see Fig. 3). The mode and average of the masses, of the cross-sectional areas and of the fall velocities over all snowfalls are 0.5 mg, 3.6 mg 1.5 mm2, 48 mm2 and 70-80 cm/s, 100 cm/s respectively. These values may be considered to represent the typical properties of snowflakes observed in the Hokuriku district. 2) The population containing the data of all snowfalls is divided into sub-populations by the interval of mass of 1 mg successively, and the conditional probability function of fall velocity is separately determined for each sub-population. These conditional probability functions can be expressed by a linear combination of several normal distributions with few exceptions. Of these normal distributions, there are two main normal distributions and each of them contributes to the corresponding conditional probability function at the rate of 30% or more. 3) For each sub-population, the average fall velocity of the normal distribution depends on the mass, though the standard deviation is roughly constant (12 cm/s) regardless of the mass. 4) The relationship between the cross-sectional area S (mm2) and the mass M (mg) is shown by the following equation on the average:
The rainfall data, for the period 1927-1976, at nine towns in Hokkaido, Japan, have been analyzed. At Muroran, a non-urban steel-producing town, an increase of thunder days and rainfall in the warm season was found during the period 1957-1976 when an increase of steel production is reported. It seems to suggest the effects of industrial activities on weather. An increase of thunder days was also found at the non-industrial commercial city Sapporo with a population of some 1.2 million, about eight times that in 1927. However the increase is not statistically significant at the 5% level.
The Meteorological Research Institute, J.M.A., installed a quartz crystal pressure gage on the sea bottom (2200-meter depth) about 110 km south-southwest of Omaezaki in August, 1978, to observe sea level variation of the tsunami. The observations began on August, 1978, and are now continued regularly. The pressure gage is confirmed to be of use as a pelagic tide gage because the comparative tidal analysis of the pressure records and the coastal sea level records at Omaezaki showed consistent relations between the two. The tidal residual spectrum of the deep sea pressure variations has an energy level about one order lower than the sea levels at Omaezaki in the frequency range lower than 0.5 cpd. The tidal residual spectrum at Omaezaki has a configuration such that the energy density decreases toward higher frequency in proportion to ƒ-5/3 with a local rise in the frequency band between 0.1 cpd and 0.4 cpd, which may be due to meteorological disturbances. The tidal residual spectrum of the deep sea pressure has also a slope depending on ƒ-5/3 on the lower frequency side but a rather gentle slope on the higher frequency side due to the high frequency noise caused by the insufficient accuracy of the pressure observations. Consequently, the tidal residual spectral energy of the deep sea pressure becomes about the same level as that of the sea level at Omaezaki in the frequency range higher than 0.08 cph. This leads to the conclusion that the accuracy of the deep sea pressure gage used here is maintained about the same level as the coastal tide gage in the frequency range analyzed here.
Thin layers with high ozone concentration and low relative humidity (less than 20%) are frequently observed around the 500-mb level from spring to summer over Tateno. One of such cases was studied by employing the isentropic trajectory analysis. This layer is found to be a part of the jet stream front and originates from the stratosphere. Intrusion of stratospheric air into the troposphere is associated with a high level cyclone and takes place in the rear of the cyclone. The sinking motion is most intense in the southern edge of the cyclone under the jet axis and flows from the cyclonic to the anticyclonic side of the jet axis.
Characteristics of the horizontal strains during the period 1931-1973∼75 and the earthquake occurrence during the period 1931-1978 in the Izu Peninsula are investigated, and the relation between them is studied. In addition, some features of mean crustal deformation associated with earthquake occurrence are discussed. The horizontal crustal deformations during this period in the Izu Peninsula are characterized by the accumulation of shear strains. The strains are consistent with those resulting from earthquakes in a region where many earthquakes have occurred, but on the whole the contribution of earthquakes has been small. The cause of the accumulation of shear strains in the Izu Peninsula in this period may be attributed to the fact that the tectonic displacement of the Izu Peninsula to the west is larger in the southern part than that in the northern part. The horizontal strains obtained by successive triangulation measurements reflect not only the elastic strains which have accumulated but also include strains caused by earthquakes which occurred during the successive measurements and also anelastic strains. The interrelations among these deformations are briefly discussed.