Hiroshi Shitara

The Direction of Prevailing Wind at Sendai Bay Coast

From every hour the observations of wind (1963-1966) at Gamo-coast along Sendai Bay (Pacific side of Japan), following results are obtained; 1) High frequency of wind blowing from land side in winter makes a sharp contrast to that from seaside in summer (Fig. 1). 2) The frequency discontineously changes in early autumn (Fig. 1). 3) The strong wind (≥10 m/sec) tends to appear not in winter monsoon season but in spring (Fig. 3).

Distribution of Cloudy or Rainy Weather in the Northern Tohoku under the Easterly Wind in Baiu Season

During the “Baiu” season, cold and humid easterly wind locally called “Yamase” often prevails over Northeastern Japan. The distribution of frequency of cloudy weather (Fig. 1) or rainy weather (Fig. 2) under such a condition was obtained. Fig. 1 shows the area of cloudy weather extends from the east, and Fig. 2 shows that rainy weather often appears along the Pacific coast and Ou-and Kitakami mountain ranges. Both types of the distribution are influenced by the higher part (>750m) in Ou and Kitakami ranges.

The Distribution of Frequency of Rainy or Cloudy Weather in the Southern Part of Tohoku District under the “Yamase” Cold Wind

During the “Bai-u” season, cold and humid easterly wind called “Yamase” often prevails over Northeastern Japan. The distribution of frequency of non-fine weather (Fig. 1) or rainy weather (Fig. 2) under such a condition was obtained. Fig. 1 shows that the area of rainy or cloudy weather extending from the east is limitted by the higher part (>1000m) in Ou backborne range, and Fig. 2 shows that rainy weather often appears on the windward slope of the mountain ranges (Ou, Kitakami and Abukuma).

High Temperature Area over a Lake due to Lake Breezes

The horizontal air temperature profile of Lake Inawashiro, Fukushima Prefecture, was observed on July 7th, 1963, a sunny summer day. A high temperature area was found over the center of the lake (Fig. 2) when lake breezes developed. The development of this high temperature area is explained by the subsidence of relatively warm air from the higher levels, probably caused in part by the development of a small anticyclonic wind system and in part by vertical air circulation over the lake. The air is cooled as it advances shoreward over the lake surface, producing the air temperature profile over the land shown in Figure 3.

“Moist Tongue” over Japan in the Baiu Season (Preliminary Report)

At the time of heavy rainfall, very humid air named “moist tongue” is found in the upper air levels over Japan. This air, extending as a tongue from a moist air to the west or to the southwest, has been repeatedly observed during the rainy periods. In this paper, the moist air area around Japan was analyzed statistically from the vie wpoint of dew-point distribution during the baiu season (June and July). The observed frequency of dew-points above 6°C., 8°C., 10°C., and 12°C. indicates that between the 1st and the 10th of June in the average of three years, 1960-1962 (Figs. 1-4) the axis of the moist area lies in South China and extends to the east; and that between the 1st and the 10th of July (Figs. 5-8) the axis lies in central China and extends to the east. Each group of figures for June and July shows that the core of the moist area exists approximately in SW China with its axis moves toward the north in the early summer when the baiu frontal zone moves toward the north.The observed frequency of high dew-points is shown in Table. Analyzing each observation, the authors conclude that the “moist tongue” appearing over Japan emanates, in many cases, from the above mentioned moist air area.

Late Frost Damage on April 29th, 1964 - Field Survey in the Igu Basin, Southern Part of Miyagi Prefecture -

A severe damage from the late frost mainly on fruit trees and mulberry, broke out over the southern district of Northeast Japan, on 29 April, 1964. The difference of the minimum air temperature from the long term average temperature shows an uneven distribution with its maximum in the southern parts of Miyagi prefecture and central parts of Fukushima prefecture (Fig. 1) . We surveyed the Igu Basin (Miyagi pref.), which is one of the core regions suffered from the damage and was distinguished from slightly damaged regions (coastal plain) by the hills 200-300 m. high. According to the field map showing the degrees of damage on mulberry leaves (Fig. 3), there are some warm islands of slightly damaged areas at the opening of the Abukuma Valley into the basin, and also there is an area where the distribution is complicated in the northern basin adjacent to the coastal plain. Such a distribution of the damage as Fig. 3 will present the key to solve the climatic nature of small basins.