青海南部牧区前冬积雪变化及其预测的关系模型研究

 利用1961—2008年青海南部牧区地面气象观测资料、74个环流特征量和北半球500 hPa高度场网格点资料,整理了地表积雪序列和雪灾年表,并对积雪的变化趋势和雪灾发生的机理进行了研究。结果表明,1961—2008年青南牧区共有16 a发生积雪灾害,占总年数的33.33%。在4 450 m以下,累计积雪量随海拔高度的升高而增加,在4 451 m以上,累计积雪量随海拔高度的升高而减小。典型多积雪年新地岛地区的冷空气偏强、高原低值系统活动偏多,新地岛的冷空气容易沿偏西北路径侵入青南高原与高空槽前的暖湿空气汇合,形成云雨的物理条件充分,降雪多、积雪厚。典型少积雪年环流形势与上述基本相反。10—12月北美区极涡面积偏大和欧亚经向环流偏强、10月欧亚经向环流偏强、11月大西洋欧洲环流型E型日数偏多、12月大西洋副高北界位置偏北均有利于前冬青藏高原高度场的偏低和青南牧区累计积雪量的偏多。这些环流因子在相反的配置下,容易导致青南牧区累计积雪量的偏少。前冬模拟预报方程对典型多积雪年和1993年以来的积雪变化趋势全部预测成功。

Modeling on Winter Snow Accumulation Depth and Its Prediction in the Southern Pastoral Areas of Qinghai

Through compiling time series of surface snow accumulation depth and snowstorm chronology based on the ground meteorological observation data in the southern pastoral areas of Qinghai from 1961 to 2008,the 74 circulation characteristics factors data and the Northern Hemisphere 500 hPa height field grid point data,the change trend of snow accumulation depth and snow disaster occurring mechanism were studied.Results showed that there were 16 years snow disasters happening in the study area during 1961-2008,with a frequency of 33.33%.Below 4 450 m altitude,the snow accumulation depth increased along with the increase of altitude,while it decreased with altitude increase above 4 451 m.In typical more snow years,the cold air from the Novaya Zemlya was stronger and the activity of plateau low value system was more significant,so that the cold air from the Novaya Zemlya easily invaded the Southern Qinghai Plateau from the northwest side and converged with the warm and moist air in front of upper-level trough;these physical conditions were benefited for the formation of cloud,resulting in more snowfall and thicker snow accumulation.Whereas,the circulation situation in typical less snow years was in the contrary.Besides,the following factors are also conducive to the low Qinghai-Tibet Plateau height field and the more accumulated winter snow depth in the southern pastoral areas of Qinghai,they are the Polar vortex area in North American is relatively larger,the Eurasia meridional circulation is relatively stronger in October-December,the Eurasia meridional circulation is relatively stronger in October,the number of days with circulation pattern of E-type in Atlantic European is relatively more in November,and the northern boundary of Atlantic’s subtropical high is relatively more northward in December.A model based on winter snow depth in the southern pastoral areas of Qinghai and these circulation factors has showed high accuracy in forecasting snow accumulation depth in the typical more snow years and the snow change trends since 1993 in the study region.