Cold summers in northeastern Japan depicted by nation-wide distribution of sunshine duration

Abstract

Coldness in summers in the northeastern Japan is a major factor which brought famines in the early modern period. In order to understand spatio-temporal structures of that condition, principal component analysis of sunshine duration at 45 stations in Japan in 1901-2020 is made. In the result of August, the 1st component corresponds to poor sunshine nation-wide with smaller amplitude in the northern Tohoku region, which appeared in 1902, 1905, 1980 and 1993. The 2nd component corresponds to poor sunshine in the northeast and rich sunshine in the southwest, which appeared in 1934.