On-site weather data were collected for Otsu Fishing Port in Hokkaido in the winter of 2003 to 2004, where freezing in winter causes significant economic damage, and the heat budget properties of the port were clarified. The net long-wave radiation was the highest in total heat loss at over 50%, the same as in the previous year. The effect of solar radiation was also significant. We also examined a numerical calculation model of ice growth/melting process. A rational calculation method for this problem, which is a moving boundary and nonlinear problem, was also presented. We confirmed that the numerical calculation method would be applicable especially to regions such as Japan where winter season is not very cold.


Harbor freezing, a phenomenon in which water in harbors freezes during winter, causes considerable economic damage to ports, harbors and fishing ports in Hokkaido, which is located in the northern part of Japan, due to the impossibility of fishing and anchorage, damage to ships and other problems. We are engaged in the development of a multipurpose freezing simulation model that can be used as a tool to provide a relative evaluation of proposed countermeasures for Otsu Fishing Port, which suffers serious damage from freezing nearly every year (Honma et al., 2002). Figure 2 shows the condition of port freezing that occurred at Otsu Fishing Port in 2000. One of the main factors behind the freezing of this fishing port is the relatively low air and water temperatures in winter. It has also been pointed out that, because the port is excavated, tidal exchange (or heat exchange) with the open sea is unlikely to occur, and also that it is difficult for produced frazil crystals and pancake ice to be removed (Kodama et al.,2003).

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