下降相 meaning in Chinese

descending phase

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 from january to march , which was consistent with the obvious descent of appearance frequency of strong ssw event after the 1990s
分析表明： 1至3月，臭氧总量的面积平均逐渐增高，这与强ssw事件频数1至3月增高同步；此外，大气臭氧总量趋势变化以1990年前后存在明显的突变， 90年代以后，北半球中高纬1 ? 3月间大气臭氧总量处于负异常阶段，这和90年代以来强ssw事件发生频数明显下降相吻合。