where, -Σ(-t) is the cold sum. Ice thickness parameters No.7 - No.9 are different from the parameter of No.6. Taking the amount of melting and growth of ice into consideration, ice thickness parameters No.7 - No.9 were estimated based on the ice thickness data around May (the time when ices stops growing) observed by airplanes or at polar stations. The ice melting proceeds faster when the ice concentration is lower, which was also considered monthly basis.
Ice thickness here indicates the whole average ice thickness including every category such as first-year ice and multi-year ice.
Wind direction (Parameter No.10)
The wind was estimated based on the surface atmospheric pressure data during 1964 to 1994. Firstly, the atmospheric pressures of primary segments were estimated by interpolating the data at polar stations. Then, the components (x, y) of the direction of wind speed were calculated by Zubov's method. By interpolating the value obtained above, the wind directions at sub-segments were calculated.
Current direction (Parameter No.11)
Using the distribution of density and the average temperature of seawater in the summer and winter of the few years, the current direction due to the density difference was calculated by the Zubov method. Based on the atmospheric pressure data at the sea level, the current direction by the wind was calculated using the Davies calculation model. The components of total currents were calculated by means of the summation of the density and wind-driven current components.
Floe size (Parameter No.12)
The ice floe size was calculated based on visual airborne observation that was carried out during 1954 to 1985 from February to August. The ice floe size distribution was estimated using a scale of 10 units shown in Table 2.2.4.
