In order to understand a general view of the cloud distribution around Japan in winter, the monthly-mean cloud distributions in the winter, 1977-1978 were made, using the visible photographs taken by the meteorological satellite NOAA-5. The cloud amount were measured on photographs on each intersection of latitudinal and longitudinal lines by 0.5 degrees over the region from 28°N to 52°N, 128°E to 152°E, only over the sea, for the period from December, 1977 to February, 1978. The cloud amount on each point is taken to be as 1 (or 0), if the cloud exists on the point (or not).
The seasonal-mean cloud distribution was obtained by averaging for the period of three months. Six axes of the cloudy areas can be set up over the Japan Sea, and four axes off the Pacific side of the Japan Islands. These axes of the cloudy areas seem to relate the upwind topography. The clear areas with lower frequency extend to the lee of the mountains and islands which prevent northwesterly wind of the winter monsoon. The clear areas to the lee of the Japan Islands were very narrow and vanish in a short distance.
In February, the band-shaped structure of the cloud distribution is striking, and the cloud amount is generally larger than those in December and January. Cloud pattern in February shifts to the south from that in January, especially in the northern part of the Japan Sea.
From the investigation of relationship between the cloud amount and synoptic situation, it is shown that the large cloud amount is associated with the lows and fronts in a synoptic scale. However, the large cloud amount which is not associated with the lows and fronts, appears when the cold air outbreak occurs. The mean cloud distribution during the cold air outbreak shows the band-shaped structure of the cloud distribution clearly.
In conclusion, the band structure of the cloud distribution appears prevalently around Japan in winter, especially at the time when the cold air outbreak occurs. The axes of the cloudy areas can be divided into four types in relationship to topography. That is to say, i) axes from the open sea surrounded by the cold land and sea ice area, ii) those continuing from the cloudy areas over the Japan Sea, iii) those to the lee of the gaps of the mountain ranges, and iv) those to the lee of the mountains.

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The cool, moist easterly wind which blows over the eastern coast of the northern Japan during summer, is called “Yamase”. The Okhotsk anticyclone indicates the formation of the wind phenomena in this area. In addition, this wind also blows while traveling anticyclones cross over the northern part of Japan.
The cool and moist Yamase Air Mass is distinguished from the other air masses. The air mass is characterized by easterly wind from the cool ocean surface, which is located in the north of Japan. The horizontal and vertical scales of the air masses are dependent on the types of the anticyclones. They are larger during the emergence of the Okhotsk anticyclone than under the traveling anticyclone. When Yamase blows, we can observe the great differnce of air temperature between the Pacific coast and the Japan Sea coast. The differnce is also greater during the emergence of Okhotsk anticyclone.
The traveling anticyclone, passing over the northern part of Japan was investigated to identify the mountain effect on the mesoscale qualitative change of the Yamase Air Mass. The results are summarized as follows:
(1) The depth of the Yamase Air Mass was about 500 meters, and a stable layer was identified above the air mass.
(2) The Yamase Air Mass approaching with fog and low cloud was influenced by mountains. Consequently, less fog and low cloud with incresing solar radiation were observed between the windward and the leeward side of the mountains, if the elevations were between 400 and 500 meters above sea level.
(3) The air temperature on the leeward side was very high in comparison with that of the windward side, and this phenomenon was seen only in a very thin layer (25 meters) near the ground.
There was a sudden decrease in the air temperature between 400 and 525 meters, because of the horizontal advection of the Yamase Air Mass. The lower boundary of the inversion layer above 525 meters coincided with the upper boundary of the Yamase Air Mass.

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This study demonstrates the shape changes of the built-up areas of Korean cities along the progress of urbanization. The shape indices of built-up areas were calculated on the 1:50000 topographical maps at the two points of time of 1920's and 1960's with the method which was proposed by Boyce, R. R. and Clark, V. A. V. in 1964. The formula is defined as Shape Index (I)=Σni=1|(r_i/Σni=1r_i·100-100/n)| where r is the radial distance as measured from the centroid of the built-up area to its edge and n is the number of regularly spaced radii. The Boyce-Clark's shape index has some merits; it can be used for other quantitative analysis, and it is unaffected by the difference scales of maps and its range is 0 to 100. In this study, n is 20.
The Q-mode cluster analysis was employed two times with 20 radii and two times with three variables which are population size, size of built-up area and Boyce-Clark's shape index. The author tries to systematize those outcomes to the study which had been analysed with the attributes and interactions of the Korean urban system. Those various approaches make us to interpret urban system in full. As the products of this analysis, the author would like to propose the model of the shape change of the built-up area as Fig. 9 and the conclusions are as follows;
1) Urbanization makes the shapes of the built-up areas more simply. So, the shape becomes to a circle steadity. The changes of shapes occur by the growth of urban system along the time serial axis.
2) Shape is varied by the interplays to the historical inertias, environments, national economic development level, change of transportation route and technique, agglomeration and diffusion of city functions, regional planning, urban system regulations and interrelating with other systems.
3) The dramatic changes of the built-up areas of Korean cites could not be observed in the period of 1920-1960. But in general, it is clear that the shape indices of 1960's decreased than 1920's regardless the growth of built-up area.
4) The population density per the built-up area becomes higher. It shows that the agglomeration of the city functions into the CBD, where the intensity of landuse is escalated by that phenomena, so many skyscrapers are constructed and vertical functional differentiations are derived. But at the same time, the tendency that the population density become higher means that the population concentration to the city is faster than the construction of the urban equipments.
5) The cluster analysis with three variables produced the greater city groups at the two points of time. The result shows dramatic change. The greater city group is consisted of Incheon, Mogpo, Gunsan, Daegu, Masan in 1920's; but it is consisted of Incheon, Daejeon, Gwangju, Daegu in 1960's. The greater city group of 1960's developed with high speed and become regional central cities to 1980. Since 1960, Korea shows the period of modern urbanization. During the period, the greater city group developed as the base cities of four economic regions of Korea (except Incheon). The development of above cities are perceived as the functional roles become stronger in the Korean urban system. The roles of above cities have been distinguished by the factor analysis with 30 variables and the analysis of the trunk telephone calls along the time serial studies, too.
6) The cluster analysis with 20 radii produced the similar outcomes. The greater city group is consisted of Incheon, Daegu in 1960's but the discernable subgroup is consisted of Suweon, Mogpo, Daejeon, Jeonju, Gwangju which are the main Korean greater cities.
Above conclusions show that the study of shape is useful for the synthetical urban system analysis.

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