Reconstruction and Analysis of January-February Snowfall in the Altay Prefecture during 1818-2006

Eight tree-ring chronologies in middle and eastern Altay Prefecture were established.The correlation between the climatic data and the chronologies was analyzed.It is found that the standardized chronology series positively correlates with the snowfall from January to February in the prefecture,and has obvious tree physiological significance.With the three chronologies YHN(t),ZLS(t+2) and HLE(t+3),the 189 a(1818-2006) snowfall from January to February can be better reconstructed,and the reconstructed equation is reliable.It is found that: 1) The reconstructed snowfall has five wetter periods above their mean and five drier periods below their mean.2) The reconstructed series has significant cycles of 2.4 a,3.3~3.4 a and 63 a periods.3) The abruptly change of the reconstructed snowfall series occurred in 1847,1901,1930 and 1986,of which the change was from more to less in 1847 and 1930,while the change was from less to more in 1901 and 1986.