A snow burst event characterized by brief heavy snowfall affected Northeast China and caused serious social impact on 26 January 2017,with the snowband generally aligned with a northeast–southwest-oriented cold front...A snow burst event characterized by brief heavy snowfall affected Northeast China and caused serious social impact on 26 January 2017,with the snowband generally aligned with a northeast–southwest-oriented cold front.ECMWF reanalysis data were used to diagnose the possible trigger mechanism.Results showed there were two stages:(a)an initial stage far away from the Changbai Mountains,and(b)an enhancement stage under the influence of high terrain.During the initial stage,the coupling of low-level frontogenesis and a favorable convergence pattern caused strong upward motion,contributing to the release of instability.When the snowband approached the high terrain during the enhancement stage,the various instabilities were triggered by the low-level frontogenesis,terrain circulation,and strong wind shear associated with the low-level jet.Further,a modified Q-vector divergence including generalized potential temperature was calculated to diagnose the vertical motion.It showed that the frontogenesis terms contributed greatly to the negative Q-vector divergence along the moist isentropes,while the pseudo-vorticity terms played a role in the regions with strong wind shear associated with the low-level jet in the warm section,suggesting both were important in stimulating the ascending motion.The regions with negative Q-vector divergence had a close relationship with the vertical structure of convection,indicating the potential to track the development of the snowband in the next few hours.展开更多
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences grant numbers XDA17010105and XDA20100304the National Key Research and Development Program grant numbers 2018YFC1507104 and 2019YFC1510400+1 种基金the Key Projects of Jilin Province Science and Technology Development Plan grant numbers 20180201035SFthe National Natural Science Foundation of China grant numbers 41775140 and 41790471。
文摘A snow burst event characterized by brief heavy snowfall affected Northeast China and caused serious social impact on 26 January 2017,with the snowband generally aligned with a northeast–southwest-oriented cold front.ECMWF reanalysis data were used to diagnose the possible trigger mechanism.Results showed there were two stages:(a)an initial stage far away from the Changbai Mountains,and(b)an enhancement stage under the influence of high terrain.During the initial stage,the coupling of low-level frontogenesis and a favorable convergence pattern caused strong upward motion,contributing to the release of instability.When the snowband approached the high terrain during the enhancement stage,the various instabilities were triggered by the low-level frontogenesis,terrain circulation,and strong wind shear associated with the low-level jet.Further,a modified Q-vector divergence including generalized potential temperature was calculated to diagnose the vertical motion.It showed that the frontogenesis terms contributed greatly to the negative Q-vector divergence along the moist isentropes,while the pseudo-vorticity terms played a role in the regions with strong wind shear associated with the low-level jet in the warm section,suggesting both were important in stimulating the ascending motion.The regions with negative Q-vector divergence had a close relationship with the vertical structure of convection,indicating the potential to track the development of the snowband in the next few hours.
