Abstract
To understand synoptically wave conditions for the ship navigation in the North Pacific, we examine the relationship between the middle and long term variations of significant wave height (SWH) in the North Pacific and the climate index (NPI: North Pacific Index) which is one of the representative climate indexes. The correlation coefficients between SWH and NPI during all the data period tend to be significantly high in the NPI region (30°N-45°N, 160°E-140°W). The correlation coefficient between the area-averaged SWH and NPI in the NPI region is also significantly high. In winter, the correlation coefficient between SWH and NPI is high in the NPI region expect its northwestern region. In spring, the correlation coefficients tend to be low in the whole region of the North Pacific. In summer, the correlation coefficients tend to be high in the northern half of the NPI region and the offshore region between the Aleutian Islands and Canada. In autumn, the correlation coefficients tend to be high in the region between the NPI region and the eastern offshore region of Japan. The correlation coefficients between the area-averaged SWH and NPI in the western, eastern and northern sides of the NPI region tend to be low in spring and high in autumn, respectively. On the other hand, in winter and summer, the correlation coefficients are scattering significantly in each sides.
