Based on the daily snowfall data from 27 meteorological stations in Qinghai Province from 1962 to 2012,the spatiotemporal variation patterns of the beginning and ending dates of snowfall and snowfall days were analyzed by means of inverse distance-weighted interpolation, and Mann-Kendall mutation test. The results show that the beginning date of snowfall in Qinghai Province mainly concentrated in September,October and November,but the ending date mainly concentrated in April and May. The earliest snowfall occurred in the Three-River headwaters region,and the latest was in the Qaidam Basin. In addition,the beginning date of snowfall in most areas of Qinghai Province was gradually delayed,but the ending date of snowfall was brought forward. The snowfall days concentrated on March,April and October( mainly light and heavy snows),and showed a decreasing trend at rates of 1- 3 days per decade. An obvious abrupt change existed in the beginning and ending dates of snowfall and snowfall days. Latitude,altitude and annual mean temperature correlated strongly with the beginning and ending dates of snowfall and snowfall days,and the correlations of the beginning and ending dates of snowfall with the average daily temperature( mean,maximum and minimum values) were different in different months. Besides,a positive correlation between snow season length and mean snowfall days existed.

Based on daily precipitation at 71 meteorological stations over Northeast China observed by the China Meteorological Administration during the 1960–2011 period, the spatial and temporal distributions of climate extremes were analyzed. Twelve indices of extreme precipitation were studied. Consecutive dry days decreased and were significant at the 0.05 level, while the other precipitation indices had non-significant decreasing trends. The increase and decrease in the aspect of precipitation extreme events showed obvious spatial differences, and change patterns of these indices were not spatially clustered. Different oscillation periods were displayed very clearly in the extreme precipitation indices. Significant periodic variations with periods of a 7-year, a 14-year and a 17-year appeared in the extreme precipitation. The contribution of extreme precipitation to total precipitation decreased, and the mean trend magnitudes were influenced by the topography for the most extreme precipitation indices from 1960 to 2011. In addition, there were significant correlations between annual total precipitation and precipitation extremes, except consecutive dry days.

Based on the daily precipitation data from 19 stations in Shaanxi Province during 1960-2011,and by using the methods of inverse distance weighted interpolation,climate tendency coefficient,M-K mutations inspection,Morlet wavelet analysis,correlation analysis,synthetic analysis,and R/ S analysis,this paper analyzed the variation characteristics of intra-annual precipitation concentration degree and concentration period and their variation tendency in the Province.In 1960-2011,the intra-annual precipitation concentration degree in the Province ranged from 0.44 to 0.66,and presented the spatial distribution characteristics of being higher in the south and north but lower in the middle part.The intra-annual precipitation concentration period ranged from 18.32-22.37 ten days,and showed comparatively small regional difference.The intra-annual precipitation concentration degree presented an increasing trend,while the intra-annual precipitation concentration period displayed an advanced tendency.The variation trends of the intra-precipitation concentration degree and concentration period all existed obvious regional differences.A decreasing abrupt variation in the intra-annual precipitation concentration degree occurred in 1974,while the postponed abrupt variation of the intra-annual precipitation concentration period happened in 1962.The variations of the intra-annual precipitation concentration degree and concentration period did not have a fixed cycle,but various cycle scales nested each other,showing stronger partial characteristics of time and frequency.In the whole province,the annual precipitation was positively correlated with intra-annual precipitation concentration degree,and also,positively correlated with intra-annual precipitation concentration period except in Hengshan of northern Shaanxi.Both in waterish and in water deficient years,the spatial distribution of intra-annual precipitation concentration degree displayed the characteristics of being higher in the south and north but lower in the middle part,while the spatial distribution of intra-annual precipitation concentration period had a greater difference.The variation tendency of the intra-annual precipitation concentration degree and concentration period in the future would keep the same with that in the past 52 years.

Based on observed data of seasonal snow cover at the Empty Cirque basin in the headwaters of Urumqi River from December 2006 to April 2007,Tianshan Mountains,we analyzed the variation characteristic about depth,temperature,water store of snow cover.The results are as follows: The snow cover was stable in the preliminary stage.With the precipitation decreasing,the depth of snow cover was increasing.Its maximum value was in the mid April 2007 and it lasted about 7 months.The maximum depth of the snow cover appeared in elevation 3830 m.With the elevation increasing,the depth of the snow cover was increasing above the elevation while decreasing below the elevation.The snow cover temperature was impacted by the temperature significantly,and it was increasing gradually with the temperature increasing during the observed period.At the same time the water store was higher than that of 1990s.

Tianshan is a snow disaster-prone area. Developing research on the variation of Tianshan snowfall is good to improve the snowstorm forecast. In this paper, based on the data of winter snowfall during 1961-2010 from twenty-one meteorological stations in the Tianshan Mountains, the spatial and temporal variability of snowfall, snow concentration degree (CD) and concentration period (CP) were analyzed with methods of regression analysis, Inverse Distance Weighted and wavelet analysis, and the winter snowfall variation in future was predicted using Rescaled Range Analysis. The results are as follows: the winter snowfall increases significantly; over the same period, snowfall' s CD and CP also increase but not significantly; the differences in spatial distribution are still significant; winter snowfall, CD and CP have different cycle variations in certain time-series, and the cycle is rather significant; the tendency of snowfall' s CD and CP on south (north) slope is different from that on north slope in terms of inter-annual change; snowfall' s CD in Tianshan decreases roughly from south slope to north slope, while the CP decreases roughly from west to east. The upward tendency of snowfall' s CD and CP on south slope shows that snowstorm will possibly increase in late winter. Although snowfall' s CD decreases on north slope, the tendency of snowfall is much significant, so north slope is still snow disaster-prone areas. In order to reduce the economic losses caused by snowstorm, relevant departments shall take timely preventive measures. In addition, to further analyze the snowfall characteristics, we need to start research work of its circulation background soon.