Nina Mateshvili, Iuri Mateshvili and Giuli Mateshvili.

Abastumani Astrophysical Observatory, Kazbegi av, 2a,Tbilisi, 380060, Republic of Georgia

Spectral photometric measurements of the twilight sky brightness in visible diapason of the spectrum under solar zenith angles 90° to 96° give a possibility to detect stratospheric aerosol stratification profiles. A comparison of such measurements with stratospheric lidar data may be mutually beneficial. The twilight photometry usually gives information about aerosol also at altitudes higher then 25 km where lidars are less sensitive. Besides that, wide spectral range of these measurements allows to estimate aerosol size distributions. They also are able to detect a wider range of particle sizes as far as they deal with the side scattering of incident light. On the other hand, the lidar measurements may bring more accuracy in altitude attribution of stratospheric aerosol features and give a higher altitudinal resolution of aerosol profiles. The twilight spectral measurements were carried out in Abastumani Observatory (42.8° N, 41.8° E), Georgia, South Caucasus after a few major volcanic eruptions, such as El Chichon and Pinatubo. In the both cases the obtained data allowed to detect the stratospheric aerosol layer of volcanic origin and to trace its subsequent development.