基于逐日积雪深度预报的藏北草原雪灾等级评估

Snowstorm Intensity Assessment in the Grassland over Northern Tibetan Plateau Based on Daily Snow Depth Forecasting

选取西藏高原北部牧区的13个气象站冬半年（11月—次年4月）的1980—2007年逐日积雪深度和最高、最低、平均气温资料,对藏北牧区草场的融雪量与气温关系进行了分析。利用线性回归模型建立融雪率和最高、最低气温的方程,给出了藏北草场的融雪日数、逐日积雪深度的计算方法,得出草场雪灾等级评估产品,实现在一场降雪后根据日常天气预报业务制作草场逐日积雪深度的预报产品,并实时评估雪灾的严重程度,为草原雪灾气象服务提供定量化参考产品。对2008—2009、2009—2010和2010—2011年的三个冬半年进行了预报效果评估,1-15d的逐日积雪深度的平均绝对误差不超过2cm;积雪日数误差不超过9d,误差在1d以内的占78.5%;雪灾等级的准确率约为84%;该方法具有较好的预报效果,能为藏北雪灾评估提供参考。该方法的缺陷在于,由于没有准确的定量降雪预报产品,故没有考虑后续降雪量的新增积雪影响。

The relationship between snow melting rate（SMR） and temperature is analyzed by using ground observation data during the winter half year from current November to the next April in years from 1980 to 2007, at 13 weather stations over the Northern Tibetan Plateau. The daily products of snow cover days, snow depth and snowstorms intensity level are offered based on the linear regression model between SMR and the maximum temperature, minimum temperature. This method may be applied to assessing the snowstorm severity on time, and providing quantitative products in meteorology for the grassland snowstorm. In assessments for three winter half years of 2008-2009, 2009-2010 and 2010-2011, the averaged absolute forecast-error of daily snow depth is less than 2cm for 1-15 days; of snow cover days is less than 9d, of which 78.5% errors are not more than 1 day; of the accuracy of snowstorms intensity level is about 84%. So, it has a better forecast function for the snow disaster assessment in the Northern Tibet. The defect is that no consideration of the new snow cover for the later snowfall, because there is no accurately quantitative snowfall forecasting products.