In the tropics, small negative anomaly is seen in 2001, part of a quasi- biennial oscillation of total ozone. Figure 2 shows the total ozone data for four central U.S. stations from1979 through 2000. Middle latitude total ozone values in the years since 1993 have not continued to decline as they had declined from 1979 to 1993. However ozone values have also not recovered to their higher 1980 values. The implication of these changes needs to be examined in the context of changes in amounts of ozone depleting gases in the atmosphere and varying meteorological conditions.
High ozone extends over the entire Arctic region.
The 1979 to 1986 base period is chosen because 1979-1986 average values are indicative of the early data record. Most notable are the positive anomalies of more than 12 percent over the Arctic region. Negative anomalies appear throughout middle latitudes. Temperatures in the lower stratosphere are closely coupled to ozone through dynamics and photochemistry. At the end of January, temperatures increased markedly at 50 hPa, in association with a large stratospheric warming.