The Determination Of Strong SSW And The Analysis Of Its Cause In The Winter In The Northern Hemisphere

In this paper, I studied the space-time character of SSW event in the mid and high latitude of the Northern Hemisphere and its affective factors, by using NCEP/NCAR re-analyzed day-by-day potential height field, temperature field, u, v and w data field, and monthly average Earth Probe - TOMS global grid data of ozone amount. At first, according to the definition of WMO, I gave the index to identify strong SSW event, and by which, I had a systemic statistic on the day-by-day temperature, air pressure, wind field in the stratosphere from January to March during the period of 1950-2002. Finally, I got 35 strong SSW events. Comparing these with Labitake' s research result, I found the index and process are rational. Secondly, I studied the climate and it's abnormity character of strong SSW. The result showed that: 1)The average yearly appearance frequency of strong SSW event was 0.66 times (about two times per three years). The average duration was 9 days. From intense winter(January) to early spring(March), the appearance frequency increased by degrees. 2)The appearance frequency of strong SSW event had obvious interannual change. From the 1970s to 1980s it happened frequently, average 1 times per year. But From the 1990s it happened less, 0.42 times per year. 3) The upper air stream circumstances along with strong SSW event mainly was separated to three kinds: the northern advance of Aleutian high pressure, the northern advance of North Atlantic high pressure, the northern advance of Aleutian high pressure and North Atlantic high pressure at the same time. Their final effect was to make polar region vortex collapse and to increase polar region temperature. 4)The occurring source of the strong SSW event had strong regional character. The northeast land of Europe-Asia was the region which strong SSW occurred most frequently.The research showed that: from January to March, the acreage average ozone gross gathered, which was synchronized with the increase of the frequency of strong SSW event. Furthermore, the change tendency of ozone gross in the atmosphere break forward and backward 1990. After the1990s, ozone gross in the atmosphere appeared negative anomaly in the mid and high latitude of north hemisphere fromJanuary to March, which was consistent with the obvious descent of appearance frequency of strong SSW event after the 1990s.We used the method of SVD to analyze the relationship of the day-by-day vertical velocity field and the temperature field of the same term in 30hPa layer. In the east of Greenland and the northwest of Canada, there were obvious correlation between the vertical velocity field and the temperature anomaly of the same term. But the stream field continuous anomaly region can primely explain the phenomenon. In the blocking region prevail on sinking air current, which lead to adiabatic warming of the atmosphere. So the the further study of strong SSW event was also one of effective approaches to improve metaphase forecast.