STRATOSPHERIC AEROSOL LAYER OBSERVED BY LIDAR SINCE OCTOBER 1976 - CONTRIBUTION TO THE PROBLEM OF HEMISPHERIC CLIMATE

During the period October 1976 to June 1978, 40 profiles of stratospheric aerosol backscattering have been recorded by lidar at Garmisch-Partenkirchen, Germany (47.5°N). Instrumentation and data acquisition and processing are described. Errors affecting the lidar data are random counting errors, errors in reconstructing a total backscattering profile, radiosonde uncertainties, use of a standard atmosphere instead of actual data, and insufficient assumptions in the calculation of the two-way transmission. These errors and their possible reduction will be discussed. The aerosol layer between 14 and 26 km varies in height and vertical extent. The value of the vertically integrated particulate backscattering coefficient exhibits seasonal fluctuations with a minimum in March and a maximum in November. The examination of these data together with measurements by other groups since 1974 reveals that the presently determined integral values are smaller than those measured before the Fuego eruption in October 1974 and that the removal of the volcanic material injected into the stratosphere lasted for about two years. The now quasi-stationary aerosol layer is probably not supplied by the presently low volcanic activity but by other sources like a global diffusion of tropospheric SO2 into the stratosphere and additional transport of aerosols by the tropical Hadley cell. Systematic measurements for years (which will be conducted at our institute) may allow conclusions to be drawn with regard to a possible anthropogenic portion of the stratospheric aerosol. Its implication on the radiative balance and the mean surface temperature on the earth and consequently on the global climate will be discussed. © 1979 Springer-Verlag.