摘要
利用2008年12月的NCAR/NCEP逐日6 h再分析资料,对本月发生的两次强寒潮事件(分别简称为过程Ⅰ和过程Ⅱ)进行了等熵面位涡分析。结果表明:(1)两次寒潮过程的爆发时间均可用低层位涡扰动的时间曲线的转折点来确认;(2)两次过程中在寒潮爆发时,都存在明显的高位涡值向下传播特征,过程Ⅱ明显于过程Ⅰ;(3)等熵面分析可跟踪寒潮强冷空气活动,等熵面位涡演变反映了高、低层冷空气的分布及活动状况;等熵面位涡高值区代表冷空气范围,等位涡线密集区代表冷暖空气对峙。寒潮爆发时,等熵面上高层高位涡向下向南传播,导致高位涡强冷空气在垂直方向上拉伸,正涡度增强。
NCAR/NCEP reanalysis daily data with 6 h interval is used for the diagnostic analysis of the isentropie potential vortieity for two processes （processⅠ and Ⅱ for short） of strong cold wave in Dee,2008. The result shows that： firstly, the time of cold wave outbreaking can be determined by the turning point of the time curve of low-level potential vorticity disturbance; secondly, there are evident features of the downward spread of high vortieity in both processes when cold wave occurs. The analysis of isentropic surface can be used to follow the track of strong cold air motion in cold waves. Also, the isentropic potential vorticity evolution represents the distribution and activities of cold air at high and low levels. The high value region of isentropie potential vortieity demonstrates the range of cold air while the concentrated region of equal constant potential vorticity lines represents confrontation of warm and cold air. When cold waves outbreak, high potential vorticity transports downward and southward at high level in isentropie surface, so strong cold air of high potential vortieity extrudes. Otherwise, the isobaric sur- face shows a shape with convex above and concave below, the cyclonic rotation enhances and positive vorticity increases. In processⅡ , cold air is supplied again, which at high level transports downward so intensely that the temperature at surface decreases rapidly.
出处
《气象科学》
CSCD
北大核心
2013年第1期102-108,共7页
Journal of the Meteorological Sciences
基金
国家自然科学基金项目(41005027
40875025
40875030)
气象灾害省部共建教育部重点实验室开放课题(KLME0905)
关键词
寒潮
位涡
等熵面
Cold wave
Potential vorticity
Isentropic surface
