引发黄渤海大风的黄河气旋诊断研究

Diagnosis of Yellow River Cyclone Induced Strong Winds over Yellow and Bohai Seas

利用NCEP/NCAR1°×1°的再分析资料、常规观测资料和风云2E卫星云图资料,分析研究2011年4月26—27日突发性黄河气旋造成黄渤海大风的物理变化过程及诊断黄河气旋发生、发展的物理机制。结果表明:这次大风是在欧亚中高纬环流发生调整,高纬不稳定小槽东移发展及东亚大槽重建的过程中发生的。突发性强烈发展的黄河气旋使黄渤海产生强偏北大风。在气旋发展初期涡度平流起了主要作用,而在气旋发展中温度平流又起了主要作用;冷锋上的斜压性对于气旋发生发展起着重要作用,斜压性有利于有效位能的释放、动能制造及气旋加强;气旋始终位于Q矢量散度梯度最大区域,有利的动力和热力条件使得能量积累,促使气旋前期发展、后期维持。高空偏西急流和低空偏南急流的相互耦合,低空暖湿气流的热力强迫,使得低层大气产生强上升运动,黄河气旋强烈发展。变压梯度、气压梯度、高空风动量下传和超低空急流的偏差风辐散的共同作用,形成黄渤海强风。

Based on NCEP/NCAR1°×1° reanalysis data, conventional observational data and the FY-2E satellite data, the physical mechanism of an emergent Yellow River cyclone which induced strong winds over Yellow and Bohai Seas during 26--27 April 2011 is analyzed. It is shown that this event occurred during the period of adjustment of Eurasia mid-high latitude circulations, east moving and development of unstable short-wave trough at high latitudes and rebuilding of East Asian major trough. A strongly developed Yellow River cyclone was the engenderer of the northerly gale winds. Vortieity advection was a key factor in the growth of the cyclone, and subsequently, temperature adveetion played an important role. The ba- roclinicity near cold front was important to the genesis and development of cyclone by transforming available potential energy into kinetic energy. As the cyclone moves, Q vectors always matched well with divergence maxima, and dynamic and thermal conditions were favorable to accumulate potential energy as well as to enhance and maintain the cyclone. Our results indicate that the strongly development of Yellow River cyclone was associated with vertical coupling between the upper westerly and lower southerly jets, thermal forcing of low level moist-warm flow, and subsequently, the ascending motion in lower layers. And the gale winds over Yellow and Bohai Seas resulted from the combined impact of isallobaric gradient, pressure gradient, downward propagation of upper level momentum and divergence of super-low-level jet.