中文摘要：

利用ECMWF的再分析资料，研究近33a来北半球臭氧的变化趋势。研究表明：（1）1979-2011年北半球4个关键区（北极、东亚、北美和西欧）的臭氧总量呈减少趋势，但减少的趋势已经减缓；（2）最近19a来，北半球4个关键区臭氧都有微弱回升的趋势，回升趋势最大在东亚地区，达到0．0579DU/a；（3）自1993、1994年以来，北半球4个关键区的冬季臭氧总量都为显著的上升趋势，上升趋势最大在北极地区，为1．1577DU/a；（4）前期（1979-1994年）四个季节的北半球中高纬基本上都为下降趋势，春季俄罗斯中北部地区下降趋势最大，为4．5DU/a，而在后期（1994-2011年）冬季挪威、瑞典、芬兰及其周边的挪威海和格陵兰海区域上升趋势最大，为1．8DU/a；（5）北半球4个关键区的下降趋势最大的层次都是10hPa，北美地区下降速率最快，为1．641×10^-8/a，而这4个区上升趋势最大的层次是3hPa，北极地区上升速率最快，为3．843×10^-8/a。

英文摘要：

Based on ECMWF reanalysis data, the ozone trends over the Northern Hemisphere （NH） in the past 33 years are analyzed. The results are shown as follows. （1） The total ozone over four key regions （Arctic, East Asia, North America and Western Europe） of the Northern Hemisphere decreased in general during the period of 1979-2011, but the downward trend slowed down. （2） For the last 19 years, a weak recovering trend was witnessed in all of the four key regions, with the maximum over East Asia （about 0.057 9 DU/a）. （3） Since 1993 and 1994, a significant upward trend of the total ozone was found over the four key regions in winter, with the maximum over the Arctic （about 1.157 7 DU/a）. （4） In the earlier period（1979-1994）, a basically downward trend was found over the mid-high latitudes of the NH, with the maximum over central and northern Russia （about 4.5 DU/a） while in the later period （1994--2011）, the maximum upward trend was found in winter over Norway, Sweden, Finland and its surrounding Norwegian Sea and the Greenland Sea （about 1.8 DU/a）. （5） The largest downward trend was found at 10 hPa over all four key regions, with the maximum over North America （about 1.641x10^-8/a） while the largest upward trend was at 3 hPa, with the maximum over the Arctic （about 3.843x10^-8/a）.