Secular and seasonal variations of winter monsoon weather patterns in Japan since the early 20th century

Abstract

Winter weather conditions in Japan are characterized by a clear contrast between the regions on the Japan Sea side and those on the Pacific Ocean side of the Japanese Islands. Weather conditions in the Japan Sea side are characterized by snowfall or rainfall under winter monsoon outbreak conditions. However, the Pacific Ocean side has fine weather because the central ridges of mountains block snow clouds coming from the Japan Sea. This particular weather pattern can easily be recognized from the daily precipitation distributions. In this study, we used the daily precipitation data recorded by the Japan Meteorological Agency since 1901 to define winter monsoon weather pattern based on the contrast in the spatial distribution of daily precipitation between the regions on the Japan Sea side and those on the Pacific Ocean side. On the basis of seasonal changes in the occurrence frequencies of winter monsoon weather pattern, we delimited the beginning and ending pentads of the winter monsoon season for each year. We aimed to clarify the characteristics of long-term variations in the lengths of the winter monsoon season and in the seasonal march of winter weather conditions in Japan since the early 20th century. The results revealed a significant decreasing trend in the lengths of the winter monsoon season since the early 20th century. We also found that the occurrence frequencies of winter monsoon weather pattern have been decreasing significantly since the early 20th century. In addition to the long-term decreasing trend, we detected an abrupt decrease in the occurrence frequencies of winter monsoon weather pattern in the mid-1980s, which suggests a weakening of the winter monsoon after the mid-1980s.

Trend Analysis of Hydroclimatic Variables in the Kamo River Basin, Japan

“…The probable reason for the discrepancy might be the differences in the terrains where the stations are located, as water vapor fluxes on different terrains are different [32]. Mountain terrain comprises about 70% of the surface in the Kamo River basin; in addition, Kumogahata station is in the mountains at an elevation of 250 m, while Kyoto station is located on a plain with the elevation of 41 m. Moreover, the weakening of the winter monsoon over Japan, which can be regarded as the distribution of winter precipitation over Japan, was reported by some studies [33,34]. However, an increase in winter precipitation was found in the Kamo River basin.…”

In‐phase transition from the winter monsoon to the summer monsoon over East Asia: Role of the Indian Ocean

“…The East Asian summer monsoon (EASM) is the most extensively investigated component because the flooding and droughts in rainy season often cause large economic losses and casualties [e.g., Huang and Sun , 1992; Wang et al , 2001; Ding and Chan , 2005; Sun et al , 2010]. In recent years, with the frequent occurrence of wintertime climatic disasters, the East Asian winter monsoon (EAWM) has attracted interests and attentions of more and more scholars especially in China, Japan and Korea [e.g., Gong et al , 2001; Chen et al , 2005; Takaya and Nakamura , 2005; Chen and Kang , 2006; Wu et al , 2006; Zhou et al , 2007, 2009; Wang et al , 2009a, 2009b, 2010; Wen et al , 2009; Li and Yang , 2010; Wang and Chen , 2010a, 2010b; Hirano and Matsumoto , 2011; Park et al , 2011].…”