GLOBAL CHANGES OF AEROSOLS - GROUND BASED MONITORING OF THE OPTICAL-THICKNESS IN POLAR-REGIONS AND CENTRAL-EUROPE

Optical thickness measurements in north polar, south polar and Central European regions are presented and discussed in comparison with earlier values. Actinometer measurements of the integral optical thickness in the Arctic (Franz-Joseph-Land) from 1933 to 1942 show an average level of about 0.22 and only minor.changes between spring and summer and from year to year. Since 1955 the spring values show a pronounced increase to 0.3 in 1985. In contrast to this behaviour, the levels in Antarctica (Mirny) are much lower (around 0.18) and fairly stable between 1957 and 1990 except for two time periods with strong volcanic activities with peaks up to 0.28. - Spectral aerosol thickness data at 500 and 1000 nm for Antarctica (G. Forster) from 1955 to 1990 indicate volcanic activity markedly with data rising from a level around 0.03 to two maxima of about 0.12. In March 1989, the boundary layer extinction coefficient at 500 nm in the Arctic reached the 79-fold of the Antarctic and the 2.5-fold of the Central Europe values at Lindenberg. The very high winter and spring aerosol extinction coefficients in the Arctic result from long-range transport and gas-to-particle conversion of NO(x) and SO2.