Spatial distributions and variations of the snow cover in the forests of Northeast China

Based on daily snow depth data from 1961 to 2008 of 156 meteorological stations in the Northeast Forest,the spatial distribution and variations of snow cover were analyzed in detail. The results show that the first snow date gradually delayed,the last snow date gradually ended earlier,snow days and snow cover gradually increased,and maximum snow depth gradually deepened from north to south and from northeast to southwest in northeast forest region. The first snow date significantly delayed at the speed of 1. 8 d /10 a from 1961 to 2008,the last snow date significantly ended earlier,with an average 1. 9 days per 10 a,the snow days shortened by 3.5 days per 10 a on average,while snow cover showed no significant tendency. The maximum snow depth showed no obvious increasing trend. The first snow date showed delay trend in 88% stations of total meteorological stations,and the site with last snow date ending earlier accounted for 95%. The snow days shortened in about 97%area of the region,and the area with snow cover shortening accounted for 58%. The maximum snow depth increased in 71% area. The first snow date,the last snow date,snow days,and the maximum snow depth have an abrupt change in 1990 s,and snow cover had no significant change,but all showed 2a,4a and 6- 8a cycle characteristics.