Development of a global stratospheric aerosol climatology: Optical properties and applications for UV

A long-term stratospheric aerosol climatology is constructed using SAGE II spectral extinction measurements, worldwide lidar observations, and time series of atmospheric turbidity and transmission data. The results contain important information for assessing stratospheric aerosol effects on ultraviolet (UV) radiation and are intended to provide more accurate stratospheric aerosol corrections for the Umkehr-retrieved ozone profiles. The record, dating from 1953 to 1997, is also useful for climate studies and for estimating errors to other remote sensing methods. A significant part of this study involves examination of the relationships between aerosol size distribution and optical properties as a function of wavelength. These relationships provide empirical means for estimating aerosol extinction at various wavelengths, including UV-B wavelengths, from a single lidar backscatter value or from an extinction value at a different wavelength. A total of 134 size distributions, reported in the literature by several investigators, were used in this analysis. The results suggest the existence of a bounded and predictable domain for aerosol optical properties and indicate distinct differences between volcanic and background aerosol regimes. This paper summarizes the data and methods used in the development of a stratospheric aerosol climatology and illustrates the resulting long-term time series of monthly and zonally averaged stratospheric aerosol optical depth at 0.320 μm. This wavelength was selected because it is close to the midpoint of the Umkehr C-pair wavelengths of 0.311 and 0.332 μm.