Analysis of Precipitation Data at Yokohama, Japan, from 1863 to 1869 Observed by J.C. Hepburn

Abstract

This study analyzed precipitation data during the 1860s in Yokohama, Japan, using observations made by an American Christian missionary, J.C. Hepburn. Hepburn's meteorological data included monthly maximum, mean, and minimum temperatures, monthly precipitation, and the number of rain days in each month. The climate during the late 1860s was characterized by large inter-annual precipitation variability during summer. We detected unusually heavy rainfall during the summer of 1868, whereas the summer of 1867 was characterized by extremely low precipitation. These trends are in accordance with precipitation patterns reconstructed from historical weather documents. Furthermore, we investigated the spatial distribution of extreme climate events in 1867 and 1868 throughout Japan. The results suggest that the unusual dryness in 1867 and wetness in 1868 were related to synoptic-scale climate in Japan, rather than local-scale patterns in Yokohama. The results from this study could be used to understand the nature of summer climate variations in Japan in the 1860s.

Overview of the Special Issue “Meteorological Disasters and Climate Variations in Historical Times”

“…Longterm historical documents, which include meteorological disasters occurring over hundreds of years, will play important roles in climate change research. Hirano et al (2018) analyzed the characteristics of rainfall fluctuations in Yokohama from 1863 to 1869, for which JMA observational data are not available, using meteorological records from observations carried out by J.C. Hepburn, an American missionary. As a result, it is revealed that the summer in 1868 was extremely rainy, whereas rainfall in 1867 was extremely small with a tendency for dry weather.…”