Analysis of Radiative Observations in Cloudy Atmosphere - Short-Wave Solar Radiation in the Earth's Atmosphere - page 236

τ 0 retrieved from the data of airborne
radiative observations for different latitudinal zones: a 17 ◦ N; b 45 ◦ N; c 60 ◦ N; d 75 ◦ N

Fig. 7.1a-d. Spectral dependence of optical thickness