Reconstructed Precipitation in Beijing during 1860－1897 Based on the Weather Records from “Diary of Weng Tonghe”

Daily weather records from private diaries are important proxy data for reconstructing historical precipitation. The authors extracted daily weather records from “Diary of Weng Tonghe” and calculated the monthly rain/snow days using these records. The annual and summer precipitation in Beijing during 1860－1897 was reconstructed using the conversion functions relating precipitation with rain/snow days. Finally, by integrating the reconstruction with the instrumental data and the reconstruction from Sunshine Rainfall Records (SRR), the precipitation during 1860－1897 in Beijing was reestimated. The results show: (1) The reconstruction based on the rain/snow days from “Diary of Weng Tonghe” is generally reliable and the reconstructed annual precipitation was about 611.5 mm; however, the precipitation in relative flood years was underestimated by the conversion functions; (2) the reestimated annual precipitation was about 701.3 mm, which might be more than that in the later half of 20th century; (3) the instrumental precipitation record in 1891 may be more than the actual value and the instrumental precipitation record in 1895 may be lower than the actual value; dry-wet grades in 1869, 1863, 1885, 1889, and 1887 may be not consistent with actual conditions. This research demonstrates the daily weather records from private diaries have great potential to reconstruct historical precipitation, but it is worthy to note that lower biases existed in the present reconstruction.