Lidar- and balloon-borne particle counter comparisons following recent volcanic eruptions

Balloon-borne particle counter measurements at Laramie, Wyoming (41 degrees N) are used to calculate the expected lidar backscatter at 0.694 mym wavelength from July 1979 to February 1982, a period which included at least four detectable perturbations of the stratospheric aerosol layer due to volcanic eruptions. These calculations are compared with lidar measurements conducted at Garmisch-Partenkirchen (47.5 degrees N) during the same period. While the agreement is generally good using only the main mode in the particle size distribution (radius approx. 0.07 mym) during approximately the first 6 months following a major volcanic eruption, a measured secondary mode near 1 mym radius, when included, improves the agreement. Calculations of the expected backscatter at 25-30 km reveal that substantial number of particles diffuse into this high altitude region about 7 months after a major eruption, and these particles should be taken into account when normalizing lidar at these altitudes. (I FU)