Tree-ring precipitation records from Baiyinaobao, Inner Mongolia since A.D. 1838
Tree-ring precipitation records from Baiyinaobao,Inner Mongolia since A.D. 1838

Correlation function analysis shows that total precipitation from April to early July (to July 10) in growing season limits the ring width of Picea Koraiensis significantly in Baiyinaobao, Xilinhot, Inner Mongolia. Thus a transfer function is designed to reconstruct the total precipitation from April to early July over the region for the last 160 years. The explained variance of the reconstruction is 49.3% (and 45.7% when adjusted for loss of degrees of freedom, N = 31, r = 0.702, F = 13.608, p < 0.0001). There are three relatively wet periods in the reconstruction which are: 1869-1875, 1886-1921 and 1943-1968, and four relatively dry periods: 1851-1868, 1876-1885, 1922-1943 and 1969-1999. Among them, the wet periods of 1886-1921 and 1943-1968, and the dry period of 1922-1943 appeared almost at the same time with those in Mt. Qilian region. Meanwhile, the dry period of 1922-1943 corresponds to high temperature and low rainfall during the 1920s and thereafter, and wetness of 1943-1968 corresponds very well to low temperature and more precipitation after the 1940s in Northwest, Northern China and the Changjiang River drainage basin. Calculation shows that the reconstruction series is significantly correlated with local dry-wet index (r = -0.234, p < 0.007, N = 143). Wavelet analysis indicates that there is a 22-a cycle in the precipitation of April to early July during 1838-1920, and an 11-a cycle during 1920-1952. No more cycles that reach 95% confidence limits are identified after 1953. The precipitation from April to early July quickly dropped into low during the 1920s. After 1950, precipitation shows a declining trend, but the reconstruction shows a tendency of increase in the late of 1990s.