Quasi-six-year Fluctuation in Summer Surface Air Temperatures in Japan

Abstract

High temperatures (H1), which appear at intervals of 4-6 years, have been noted in the summer surface air temperature (hereafter, referred to as summer temperature) in Japan. The interval between H1 years is 6 years in most cases. This fluctuation of summer temperature in Japan (quasi-six-year fluctuation, hereafter) is distinct in the northern part of the country, but it is also seen in other areas of Japan, except in the Southwest Islands. Summer temperatures for other years of the cycle, also show the following characteristics in Northern Japan: (i) cold temperatures appear in years of H1 - 2 (2 years before H1), and H1 - 1 (1 year before H1); (ii) years of extremely low temperature are included in the H1 - 1 group; (iii) warm temperatures appear in H1 + 1 (1 year after H1), and (iv) cold temperatures appear in H1+2 (2 years after H1). The period of 6 years also appears in fluctuations of sea surface temperature in the North Pacific Ocean (Saiki and Nagasaka 1986). High correlation between the quasi-6-year fluctuation of summer temperature in Japan, and fluctuation of sea surface temperature in the North Pacific Ocean, suggests that these two quantities are closely related.