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摘要: 为探讨山东半岛北部冷流降雪的气候条件及其形成机理,采用经验正交函数(EOF)方法有效地分离出系统性降雪和局地降雪即冷流降雪.通过回归和合成分析揭示了冷流降雪多发时典型的环流特征是低层温度场落后高度场,强冷平流伴随冷槽加深,西北风加强.在此环流背景下,低层大气层结不稳定、充分的热量、水汽输送是局地降雪的主要气候原因.根据热力、水汽和层结等条件的分析表明,12月具备最佳降雪条件,与观测事实一致.沿海边界层的斜压结构、陆面摩擦与地形强迫,使上升运动加强,形成了半岛局地降雪特有的空间分布型.进一步分析表明,低频重力内波有可能成为激发对流,组织降雪的动力因子之一.Abstract: Two kinds of snows, called systematic snow and cold outbreak snow, at northern Shandong Peninsula were identified by using EOF (empirical orthogonal function). Forming mechanism of coldoutbreak snow, namely cold snow, discussed climatically. The favorable circulation pattern is lowlevel strong cold advection accompanied by deepening trough with NNW flow strengthening. Then heat flux and water vapour from the sea, as well as lowlevel stratification instability play an important role. The results show that thermal regime and evaporation in December in a year provide more advantaged capability for local snow, as accords with the observational facts. It is baroclinic boundary layer and land friction and orographic forcing that strengthen convection, so that peculiar spacial snow pattern forms at Shandong Peninsula. Further study shows that lowfrequent inner gravity wave is one of important dynamical factors which are able to inspire convection and organize snow.
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