| Popis: |
Ozone trends, derived from 1979–1996 Dobson spectrophotometer total ozone data obtained at five U.S. mainland midlatitude stations, averaged −3.4, −4.9, −2.6, −1.9, and −3.3%/decade for winter, spring, summer, and autumn months, and on an annual basis, respectively. At the lower latitude stations of Mauna Loa and Samoa, corresponding-period annual ozone trends were −0.4 and −1.3%/decade, respectively, while at Huancayo, Peru, the 1979–1991 annual trend was −0.9%/decade. A linear trend approximation to ozone changes that occurred since 1978 during austral daylight times at Amundsen-Scott (South Pole) station, Antarctica, yielded a value of −12%/decade. By combining 1979–1996 annual trend data for three U.S. mainland stations with trends for the sites derived from 1963–1978 data, it is estimated that the ozone decrease at U.S. midlatitudes through 1996, relative to ozone present in the mid-1960s, was −6.7%. Similar analyses incorporating South Pole data obtained since 1963 yielded an ozone change at South Pole (daylight observations) through 1996 of approximately −25%. South Pole October total ozone values in 1996 were lower than mid-1960s October ozone values by a factor of two. Trend data are also presented for several shorter record period stations, including the foreign cooperative stations of Haute Provence, France; Lauder, New Zealand; and Perth, Australia. |
Plný text