On the Mechanism of a Terrain-Influenced Snow Burst Event during Midwinter in Northeast China |
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| Authors: | Na LI Baofeng JIAO Lingkun RAN Xinyong SHEN Yanbin QI |
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| Institution: | Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China;Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China;Key Laboratory of Meteorological Disaster, Ministry of Education/Joint International Research Laboratory of Climate and Environment Change/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, Nanjing 210044, China;Key Laboratory of Meteorological Disaster, Ministry of Education/Joint International Research Laboratory of Climate and Environment Change/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, Nanjing 210044, China;Jilin Weather Modification Office, Changchun 130062, China |
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| Abstract: | Short-duration snow bursts with heavy snow represent one type of hazardous weather in winter which can be easily missed by the winter weather warnings but often results in great hazards. In this paper, the mechanism for the occurrence of such events was investigated with the aid of a localized terrain-influenced snow burst event in Northeast China. The snow burst was produced by an eastward-moving cold-frontal snowband which encountered the downstream complex terrain of the Changbai Mountains and intensified. To ascertain the role of orography on the snow burst, numerical experiments,together with a parallel sensitivity experiment removing Changbai Mountains, were performed to attempt to distinguish the contributions of cold-frontal system and orographic effects to produce the heavy snow. Diagnosis showed that without the influence of Changbai Mountains, the release of conditional instability(CI) and inertial instability(II) within a weak frontogenetical environment was responsible for the snowband maintenance. Orographic effects played important roles in enhancing the snowband and increasing the snowfall intensities. The enhancement mechanism was related to the interactions of the cold-frontal snowband and the topography. On the one hand, orographic frontogenesis and persistent ascent, created by orographic gravity waves over the terrain, greatly enhanced the orographic lifting. The intensification of the lifting promoted the release of CI and thus enhanced the snowfall. On the other hand, pre-existing orographic instabilities were released due to the passing of the cold-frontal snowband, which could also serve to intensify the snowband over terrain and thus increase the snowfall. |
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| Keywords: | terrain-influenced snow burst snowband instability lifting |
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