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Keywords:

  • Beijing;
  • daily weather records;
  • historical diary;
  • precipitation reconstruction

Abstract

Daily weather records from a historical private diary provide important data for studying historical climate change. We compiled daily weather records from the Weng Tong-He Diary and counted the number of monthly precipitation days during 1860-1897 AD for Beijing; then, using the number of monthly precipitation days, we reconstructed the seasonal precipitation using regression models relating the precipitation and precipitation days. The findings show that the monthly mean number of precipitation days for 1860-1897 was greater than that for 1951-2009 by about 1 d month−1 and that the summer (June to August, JJA) precipitation for 1860-1897 was 471.8 mm greater than that for 1951-2009 by about 15.5%. The JJA precipitation of 1860-1897 had not only inter-annual variations but also inter-decadal variations that were characterized by less precipitation before 1886 (about 421.9 mm) and more precipitation thereafter (about 550.7 mm). As a consequence, the JJA precipitation of 1860-1897 showed an evident positive trend with a rate of about 57.9 mm per decade. These precipitation variations were confirmed by other datasets. However, it is worth noting that our reconstruction underestimates the historical precipitation values (by about 22.5%) because of rainfall/snowfall events missed in Weng's diary and the poor ability of the regression models to capture extreme years. In the future, new methods of reconstructing precipitation with the consideration of missed rainfall/snowfall events are needed. Copyright © 2012 Royal Meteorological Society