Twilight with Aerosols

Here are two new twilight images that I rendered with aerosols. I haven't tone-mapped either of these images—they are display-linear. In the second image, the sun is lower, there is a lower concentration of aerosols in the atmosphere, and the ground has a desert-like reflectivity. Because the aerosol concentrations and ground reflectivities differ, the images are not directly comparable, but I believe that a few of the differences are due to factors besides the aerosols. Based on my research (including Color and Light in Nature and The Influence of Ozone and Aerosols on the Brightness and Color of the Twilight Sky) and observations, at −4.8° I would expect a more defined twilight arch, an area of low saturation purple above the twilight arch, and more saturated blue in the zenith direction. All of these phenomena seem to be present in the −4.8° render.

−3° solar elevation angle.

−4.8° solar elevation angle. Half the amount of aerosols as in the
image above.