| dc.description.abstract | In recent three decades, scientists discussed widely about the blocking high which may cause the persistence of the weather system. What are the climatic features of the blocking in Northern Hemisphere? For the duration of the blocking, what kinds of factors induce the warm core? And how do the vorticity and the stability interact with each other?
In this research, a blocking episode is said to be a closed region and persist more than 5 days. We used weather maps in 500hPa from June 1996 until May 2000 to gather the blocking events. There are 292 blocking episodes (about 32 episodes per year) in the duration. The result shows that the frequency of the blocking has two maximums, May to June and December.
In order to realize the structure and the duration of blocking deeply, we chose two cases to diagnose and analyze temperature and potential vorticity. The first blocking event of 20-day duration occurred from 2 through 21 June 1998 over the north eastern Asia. And the other blocking which persists 19 days occurred from 7 through 25 March 2000 over the Northern Pacific and Alaska.
The warm core of the first blocking event which occurred during the early summer appears from 300hPa through 500hPa. However, the warm core of the early spring blocking event appears on the lower troposphere where is below 600hPa. From the results of the temperature diagnosis, the horizontal warm advection induces the warm core of the blocking. In the vertical motion, the vertical cold advection and the adiabatic warming are contrary. Subsequently, the result of the potential vorticity reveals that as the blocking enhances, the stability increases and the resolute vorticity decreases. | en_US |