SESSION I: UPPER TROPOSPHERIC/LOWER STRATOSPHERIC OZONE CLIMATOLOGY

摘要

The focus of Session I was on global observations that are required for documenting changes in the vertical distribution of upper tropospheric and lower stratospheric ozone. There has been statistically significant increases in free tropospheric ozone concentration in some areas of the northern hemisphere and, at the same time, a global decrease in lower stratospheric ozone concentration. The total ozone continues to decline by an average rate of 3% per decade since the late 1970's. Recent WMO assessment reports characterize the state of knowledge regarding tropospheric ozone trends to be very sketchy. The majority of stations measuring the vertical distribution of ozone are located in northern mid-latitudes. There are about 15 of such stations with long-term records longer than fifteen years, and most of these are located in North America, Europe and Japan. In addition, there is one station in Australia and one in Brazil, however with periods with a measurement frequency less than one sonde per week. In general, the data quality is uneven between these stations. If a better assessment is to be made of ozone impacts on climate, research must establish the trend in ozone concentration around the tropopause region as a function of latitude and season. This could be achieved if the WMO Global Ozone Observing System (GO3OS) is expanded, especially in the tropical regions in South America, the continental Asia and Indonesia, as recommended by the Research Managers reports of the Vienna convention for the protection of the ozone layer, or by coordinated measures of the same type and magnitude.