Relation Between an East Asian Winter Monsoon Index and Regional Wave Characteristics at Middle-North Coast of Japan

Abstract

Variabilities of regional wave characteristics are influenced by changes in global and local meteorological forces. It is therefore important to investigate the relations between them in order to obtain deeper physical understanding on the variabilities in wave intensities. In this study, focus is placed on the variation of wave characteristics along the coastline facing the Sea of Japan where the seasonal change in wave climate is significant. Since the influence of East Asian Winter Monsoon (EAWM) is considered to play an important role during winter at the study area, an attempt is made to clarify the influence of EAWM on the wave variabilities at Kanazawa and Wajima ports located on the middle-north coast of Japan. For this purpose, the long-term variations in wave records at Kanazawa and Wajima are analyzed for the last decades. The year-to-year variations of monthly-mean as well as winter-mean significant-wave height and period are examined and the correlations with two meteorological indices related to EAWM are analyzed. Among the existing indices representing the EAWM intensity, the EAWM index proposed by Jhun and Lee (2004) (EAWMI) and a Far East Zonal Index (FEZI) are adopted in this study. The variabilities of these indices are inspected and the correlation with wave properties during winter season are estimated. Similar analysis are conducted for several climate indices related to various meteorological phenomena in Northern Hemisphere, such as Arctic Oscillation (AO), West Pacific (WP), and North Pacific Index (NPI). The winter wave characteristics indicate substantial correlation with EAWMI and FEZI in general, while the correlations with other climate indices are found to be generally weak at the study area. The results demonstrate the intensity of the winter wave at the observed sites are strongly influenced by the intensity of EAWM especially in early winter.