The polarization is more sensitive in Blue channel than the Red channel due to the fact monomers are much smaller than the wavelength of the Red channel. As a result, a wider monomer size range can produce the near-perfect polarization observed in the Red channel. On the other hand, the maximum value of the polarization in the blue channel is given in a rather larger range ( 85% - 90% in Blue vs. ~98% in Red) which results about the same monomer size range obtained both in Red and Blue channel.
The constraints on the refractive index come from single scattering albedo ( SSA) observations. Like the phase functions initial values of the SSA measured during the Huygens probe descent was revised in (Doose et al., 2016). Although these updated SSA data yield better agreement with the constraints from the phase functions and polarization data, there is still some disagreement in the Blue 80km measurement between comparison of SSA and phase functions. Within 5% relative error there is no model particles which matches both the DISR’s phase functions and SSA data among \(5\times 10^{5}\) model aggregates.
The fact that the SSA changes throughout the atmosphere while the phase function appears to be constant requires car
It has been speculated that some condensation at the aerorosol surface occur in the lower atmosphere resulting in decrease in absorption while the phase function stays relatively constant. However,
The Final Report
I searched for the best-fitting phase functions in two different ways. In the first method, I found two-parameter ranges for each wavelength channel. Even though I adopted a single phase function throughout the atmosphere for each channel, SSA observations provide constraints on the refractive index at two altitudes. Therefore for each layer, a unique parameter ranges can be found by simply selecting the model aggregates which agree with all three observations (SSA, phase function, linear polarization). This method filters out much more model runs than the second method discussed below.
On the other hand, there is almost no model that passes all the filters at 80 km in the Blue channel without allowing at least 10% error in SSA. This could be due to the error in SSA observation or the blue phase function at this level given in the DISR model. In the DISR model, both in original
(Tomasko et al., 2008) and revised version (Doose et al., 2016), Blue phase function is constant throughout the atmosphere while the SSA is changing. It has been suggested by
Larson et al. (2014) and Doose et al. (2016) that some condensation at the aerosol surface occurs in the lower atmosphere resulting in a decrease in absorption while keeping the phase function relatively constant. However, the fact that our model does not produce any aerosol matching all the constraints within 5% accuracy might suggest either changing phase function with the altitude or some inaccuracy in SSA measurement though it is still possible that our model might also be the source of this apparent disagreement.
Table 1 and figure 2 & 3 summarizes of the parameters of the haze particles. Constraints from the Red channel provide the same parameter range at each altitude except for the imaginary part of the refractive index. This is consistent with the observation as the SSA measurements imply that more absorbing particles are found at higher altitudes while the size of the aggregates is somewhat constant
(Doose et al., 2016; Larson et al., 2014). Nevertheless, in the blue channel, there is no indication of any change in the refractive index, which does not agree with the decreasing SSA with altitude as measured by DISR. Thus allowing larger error in the SSA comparisons for the blue-80 km helps to find some matching phase function with the cost of some disparity among the constraints.
Due to the problem in the blue 80 km, I applied a slightly different algorithm in the second method. In this method the algorithm first finds the monomer number and size ranges of the aggregates which fits to the DISR phase functions and the measured maximum polarization within 5% error limit.
as the second method of comparison, I analyzed the SSA observations to obtain the constraints on the refractive index independently within the limit of range obtained from the phase function and maximum polarization comparisons. This method provides more consistency among all the constraints at different altitudes, although with a more extensive parameter ranges
Table 2 summarizes the haze particle parameters obtained by the second method. These results obtained by finding the model-aerosols within 5% accuracy to all the observations (Phase function, maximum polarization, SSA) except at the backscattering angles where ~15% accuracy allowed for the Blue channel and ~10% error for the Red channel.