Till recently no instrumental data in Japan were believed to exist. Their addition to the previous backward extension of Japanese series, as based on the recently recovered intermittent Dejima/Nagasaki series 1819-1878, implies that the 19th century extension of the Japanese instrumental record no longer contains major temporal gaps. Now the corrected and homogenized monthly temperature and pressure of Tokyo, Yokohama, Osaka, Kobe, and Nagasaki are ready for scientific use. The recovered data were used for a preliminary calculation of the West-Japan Temperature (WJT) series, which is a representative temperature series for the area. The existence of a warm epoch in the 1850s over W-Japan and a downward temperature trend till the early 20th century, as previously inferred from documentary data, is confirmed from the WJT data.

This paper introduces the existence of 19th century instrumental meteorological data in Japan. Then we describe about data itself, such as observer, observed elements, schedule of observation, instruments, and also historical background of the records. In the end, we also describe with emphasis on climatological significance of the record which covers spatially and temporally blanc spot over East Asia.