黄、渤海大风的次天气尺度环流特征及其应用

选取2008年12月出现在黄、渤海的一次大风过程,采用常规观测资料和NCEP全球再分析资料,对大风期间的次天气尺度特征及其与天气尺度系统之间的相互作用进行了诊断分析。结果表明,黄、渤海大风区的次天气尺度环流具有明显的波动特征,这种波动结构的维持与否和大风期间的天气尺度背景密切相关。黄、渤海位于高空槽前,波动结构维持,该区域从次天气尺度系统获得正涡度和动能,气旋发展,大风形成。中纬度斜压带东南移至黄、渤海上空,波动结构遭到破坏,消耗次天气尺度系统涡度,气旋减弱,但低层大气仍获得次天气尺度系统动能,大风维持。在与高空槽相互作用的过程中,虽然次天气尺度环流有不同的分布特征,但低层大气若获得次天气尺度动能,则有利于动能输入地区的风速增幅和大风持续,若消耗次天气尺度系统动能,大风停止。次天气尺度动能大值区主要在850hPa以下的低层。

Characteristics of Sub-Synoptic Scale Circulation of Strong Gale in Yellow Sea and Bohai Sea

Using the conventional observation data and NCEP/NCAR global reanalysis data with 1°×1° resolution,a strong gale processes occurred in Yellow Sea,Bohai Sea and their coastal areas in December 2008 are analyzed.The sub-synoptic scale features of strong gale are analyzed and the conversion of kinetic energy and vorticity in the strong gale and sub-synoptic scale systems during strong gale are calculated.The results indicate that the sub-synoptic scale stream fields exhibit a kind of wave structure during strong gale.Whether the wave structure maintained during the strong gale is closely related to the synoptic background.The circulations of Yellow Sea and Bohai Sea locate in front of a westerly trough,the wave structure is maintained.The transportations of the kinetic energy and positive vorticity from sub-synoptic scale systems are favorable to the formation of the strong gale and the development of the low.The circulations of Yellow Sea and Bohai Sea locate in the west of westerly trough,the wave structure is destroyed.The positive vorticity of sub-synoptic scale system is consumed and the kinetic energy is provided from synoptic scale system,which leads to the decrease of the low and the substation of the strong gale.More kinetic energy obtained from the sub-synoptic scale system in lower atmospheric layer is the dominant factor to identify whether wind will intensify or weaken rapidly.The maximum kinetic energy of sub-synoptic scale system is located in the layer below 850 hPa.