## 3 Instrument and Simulation Assumptions
### Simulation Assumptions  
#### 3.2.1 Aerosol Model  
The optical and microphysical characteristics of global aerosols vary greatly throughout both space and time. The climatic variables that control their removal and transport processes have significant impacts on their vertical and horizontal dispersion. There is a large range of values for the optical and microphysical characteristics of different forms of aerosol [33]. A theoretical analysis employing every form of aerosol is a difficult and unrealistic method. In order to simplify this method, previous studies have often analyzed some typical aerosol types (such as fine-dominated and coarse-dominated types) [7; 28; 34]. We hope to use a more realistic aerosol model classification while building a more sophisticated ALH retrieval framework for the Chinese region in order to explore the ability of UV multi-angle polarization measurements to undergo ALH retrieval for different aerosol types. Based on the ground-based remote sensing measurements of the Sun-sky radiometer Observation NETwork (SONET), ten fundamental aerosol models used in China were derived in a cluster study by [PERSON] et al., and the classifications are summarized in Table 3[35]. The ten clusters suggest five typical fine particle aerosol models and five coarse models, including urban polluted, secondary polluted, combined polluted, polluted fly ash, and continental background, summer fly ash, winter fly ash, primary dust, transported dust, and background dust. Table 4 lists the details of the microphysical parameters, including the total aerosol volume (\(\mathbf{V_{0}}\)), effective radius (\(r_{\text{eff}}\)) and variance (\(v_{\text{eff}}\)) as well as the refractive index, as shown in the results in Figure 2. In the fine-particle size range, there are five single-peak aerosol models (F-ULW, F-UHS, C-ULW, C-UHS, and C-UNW) and five double-peak (F-BLW, F-BNS, F-BNM, C-BNM and C-BHM) aerosol models. It should be noted that \begin{table}
\begin{tabular}{c c c} \hline \hline
**Mode** & **Aerosol Type** & **Description of Characteristics** \\ \hline \multirow{8}{*}{Fine Mode} & Urban polluted (F-ULW) & Urban-polluted fine-mode aerosols with high particle concentrations \\ \cline{2-3}  & Continental background (F-UHS) & Background fine-mode aerosols with low particle concentrations \\ \cline{2-3}  & Secondary polluted (F-BLW) & Secondary aerosols containing mainly polluted particles with low refractivity and a higher scattering capacity \\ \cline{2-3}  & Combined polluted (F-BNS) & Mixture of direct anthropogenic emissions and secondary aerosols with high light absorption \\ \cline{2-3}  & Polluted fly ash (F-BNM) & Mixture of anthropogenic-polluted particles and fine fly ash particles with large submicron fine particles \\ \hline \multirow{8}{*}{Coarse Mode} & Summer fly ash (C-ULW) & Background of fly ash coarse particles with low light absorption, for example, natural emissions of primary organic aerosols \\ \cline{2-3}  & Winter fly ash (C-UHS) & Background of fly ash coarse particles with high light absorption, for example, fly ash polluted by anthropogenic components \\ \cline{2-3}  & Primary dust (C-UNW) & Coarse particles of natural dust with a very high volume concentration \\ \cline{2-3}  & Transported dust (C-BNM) & Dust particles after long-term transportation and sedimentation \\ \cline{2-3}  & Background dust (C-BHM) & Background dust suspended over continental regions with a large coarse standard mode \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Aerosol model classification with SONET [35]. the double-peak feature may not be obvious, because one small peak may be covered by another big peak [35]. The scattering phase matrix \(\mathbf{P}\) is simulated using a linearized Mie code once these microphysical characteristics have been input:  
\[\mathbf{P}= \begin{bmatrix}\text{P}_{11}&\text{P}_{12}&0&0\\ \text{P}_{21}&\text{P}_{22}&0&0\\ 0&0&\text{P}_{33}&\text{P}_{34}\\ 0&0&\text{P}_{43}&\text{P}_{44}\end{bmatrix}