nai

Project Progress

Our best violet/uv models were constructed by extrapolating the optical depth and single scattering albedo derived from DISR observations, but then making minimal adjustments to them to fit the observed violet channel fluxes. The phase function was computed from the Mark Lemmon algorithm for these wavelengths. The optical depths in the three altitude regions were revised slightly from the power laws given in figure 46 of Tomasko et al., 2008. The new values are

Above 80 km: τ = 1.096E07*λ-2.343
30 – 80 km: τ = 3.505E04*λ-1.486
Under 30 km: τ = 5.859E02*λ-0.9555

(λ in nm)

The single scattering albedos were extrapolated (and then adjusted) using polynomial fits vs. wavelength.

Above 144 km: w0 = 0.0910 + 2.4393*λ – 1.7313*λ2
30 – 80 km: w0 = 0.8360 + 0.09691*λ+ 0.2559*λ2
Under 30 km: w0 = -0.5089 + 5.5159*λ – 5.0938*λ2

We also calculated diurnal-average solar fluxes at 400 nm shown in Figure 1. The seasonal pattern shown in Fig. 1 is a familiar one, with greatest solar flux at southern latitudes near northern winter solstice (due to Saturn’s perigee being nearly in phase with winter solstice), but the latitude of maximum solar flux is displaced toward the equator relative to calculations of the direct solar flux due to the effects of diffuse transmission through a thick atmosphere. These calculations enable estimates of possible surface chemical reactions stimulated by short-wave solar flux.

Reference:

Tomasko, M.G., L. Doose, S. Engel, L.E. Dafoe, R. West, M. Lemmon, E. Karkoschka, C. See, A model of Titan’s aerosols based on measurements made inside the atmosphere, Planetary and Space Science 56, 669–707, 2008.