The Tree-ring Record Of Relative Humidity From May To Julysince 1890 From Qinglong Region, Hebei Province

Tree-rings have been considered as one of the best known archives in the past climate research field with their high resolution in time and reliability in cross-dating. The study of humidity is essential for better understanding the past climatic variations, however, there were few long-term humidity reconstructions based on tree-ring widths worldwide.In our study, the mean May-July relative humidity reconstruction curve was carried out using the Chinese pine tree(Pinus tabulaeformis Carr.) from the Qinglong region in northern China. The conclusions are listed below:1 To eliminate the non-climate signal in tree ring width series, the ARSTAN program was employed to remove the growth tendency and standardize the chronology. Three tree ring chronologies(STD, RES and ARS) from 1890 to 2012 were carried out.2 The correlations between RES chronology and climate factors were calculated, which demonstrated that RES chronology correlates with mean relative humidity from May to July significantly and the correlation coefficient is 0.625(p< 0.0001).3 Based on the correlation analysis, mean relative humidity reconstruction(May-July) in Qinglong region since 1890 was carried out using tree ring RES chronology. The reconstruction explained 39.1%(38.0%, after adjustment for the loss of degrees of freedom) of the instrumental variance during the calibration period(1957-2012). On the decadal scale, there are five high-value MRH5-7 intervals(1895-1899, 1906-1914, 1924-1926, 1950-1955, 1984-2000) and five low-value MRH5-7 intervals(1900-1905, 1917-1921, 1927-1949, 1956-1973, 1975-1981)4 The MTM of spectral analysis was performed on our reconstruction, and significant high-frequent peaks were found at 5.20-year, 4.20-year, 4.03-year, 3.86-year, 3.58-yearand 2.21-yearinterannual cycles, which demonstrated that ENSO might have influence on the climate in Qinglong region.5 Tangshan drought/flood index and mean relative humidity reconstruction significantly correlate with Spearman rank correlation coefficient of r =-0.394(n = 111, p< 0.001). Qinglong relative humidity curve also have a significant correlation with the relative humidity reconstruction in the nearby Yiwulü Mountain region. The correlation coefficient r equals 0.295(n = 122, p< 0.001). Combined with spatial correlation with CRU sc PDSI, our reconstruction reflects the drought/flood changes to a certain extent around the study area.