北半球阻塞高压的维持Ⅰ:准地转和Ertel位涡分析

ON MAINTENANCE OF BLOCKING ANTICYCLONES OF NORTHERN HEMISPHERE PART 1:QUASI-STROPHIC AND ERTEL POTENTIAL VORTICITY ANALYSIS

中文关键词:  阻塞高压  位涡  北半球

英文关键词:Blocking anticyclone  Potential vorticity(PV)  Northern Hemisphere

中文摘要:

      从北半球不同地区的4个阻塞高压个例,研究了阻塞高压维持机制及其地域性差异。对阻塞高压区域300hPa时间平均准地转让涡低值区的维持机制的分析表明,该位涡低值区的维持机制存在显着的地域性差异。其中,在2个太平洋阻高个例中,时间平均流的位涡平流使低位涡向阻高西北部输送,从而有利于位涡低值区经向度的维持；时变扰动的位涡输送则有抵消平均流作用的倾向,从而对位涡低值区的维持起耗散作用。在大西洋和东亚阻高个例中,平均流的位涡平流使低位涡区向东移动,而时变扰动的位涡输送则有抵消平均流位涡平流的作用,从而有利于位涡低值区在原地稳定维持。以上主要是相对涡度输送的差异所致。等熵面Ertel位涡分析表明,阻高区域330K时间平均等熵位涡低值区的维持机制与300hPa时间平均准地转位涡低值区的维持机制十分相似,从而表明以上等压面准地转位涡分析可以近似用来代表等熵Ertel位涡分析。

英文摘要:

      In this paper, maintenance of blocking anticyclones are invested with four observed blocking anticyclones in different regions of Northern Hemisphere. It has been shown that there exists distinct region-dependent differences in the maintenance of time-mean quasi- strophic potential vorticity(PV) low in 300hPa within the bucking regions. In the two Pacifis blocking cases, the PV advection by time-mean flow tends to flow the low PV to north western part of the blocking highs and thus is benefit to the maintenance of the blockings' strength. The PV transfer by eddy tends to cancel the PV advection by mean flow. In the Atlantic and Asia blocking cases. however. the advection by mean flow tends to flow the low PV pattern eastward. The PV transfer by eddy has a tendency to advert low PV to western part of the ridges and to balance the advection by mean flow. Therefore. in these two cases it is the eddy that is benefit to the blockings'maintenance at quasi-stationary state. Very similar results are obtained with respect to maintenance of the time-mean Ertel PV in 330K surface. Therefore, in the blocking cases, the quasi-geostrophic PV analyses can be used to represent the Eretel PV analyses.