TRENDS OF OZONE IN THE TROPOSPHERE

Using a set of selected surface ozone (nine stations) and ozone vertic al profile measurements (from six stations), we have documented change s in tropospheric ozone at a number of locations. From two stations at high northern hemisphere (NH) latitudes there has been a significant decline in ozone amounts throughout the troposphere since the early 19 80s. At midlatitudes of the NH where data are the most abundant, on th e other hand, important regional differences prevail. The two stations in the eastern United States show that changes in ozone concentration s since the early 1970s have been relatively small. At the two sites i n Europe, however, ozone amounts increased rapidly into the mid-1980s, but have increased less rapidly (or in some places not at all) since then. Increases at the Japanese ozonesonde station have been largest i n the lower troposphere, but have slowed in the recent decade. The tro pics are sparsely sampled but do not show significant changes. Small i ncreases are suggested at southern hemisphere (SH) midlatitudes by the two surface data records. In Antarctica large declines in the ozone c oncentration are noted in the South Pole data, and like those at high latitudes of the NH, seem to parallel the large decreases in the strat osphere.