## 5 Discussion
### The Influence of Multi-Angle Measurements  
The scattering angle determined by the satellite observation geometry often determines the Rayleigh scattering and aerosol scattering, which has an important impact on ALH retrieval. Based on multi-angle satellite observations, it should be determined whether the height information obtained by the number of observation angles is sufficient for ALH retrieval. To explore the ALH inversion potential corresponding to polarization multi-angle measurements when the number of observation angles is further increased from 1 to 14, detailed geometric parameters are shown in Table 1. In Section 4.2, Figure 8 shows that even with multi-angle observations such as MAPMU with five viewing angles, it is  
Figure 7: The DFS of H from multi-angle radiance measurements (**a**,**b**) and adding DoLP measurements (**c**,**d**), as well as the posterior error uncertainty reduction between these two types measurements (**e**,**f**) under different aerosol conditions for ten aerosol models over vegetation surface. (**a**,**c**,**e**) represent fine mode aerosol types and (**b**,**d**,**f**) represent coarse mode aerosol types. difficult to retrieve ALH information using only intensity measurements in the UV band (DFS \(<\) 0.5). Therefore, in this section, following the addition of the polarization measurements, we examine how the DFS of ALH depends on the quantity of the observation angles to analyze whether increasing the observation angle can improve the ALH retrieval, particularly for coarse mode aerosols (C-BHM and C-BNM). When the retrieval involves multi-angle observations, the angles are selected according to the quantification of the intensity measurements with H using the Jacobian matrix from the highest (sub-satellite point) to the lowest values. Through this method, we get the following conclusions:  
1. Figure 8a,b show that the increase in the DFS with the angle number in fine mode is larger than that in coarse mode. When the angle number is 1, even in the F-UHS type with the highest DFS for fine mode, the value is only 0.28. Combined with the single-angle observation presented in Figure 9, it can be seen that, under the same conditions, when the scattering angle is around 90\({}^{\circ}\) and F-UHS is 120-150\({}^{\circ}\), the DFS can approach 0.5. In that case, the use of single-angle polarization measurements to retrieve ALH is often limited, so the development of multi-angle polarization sensors has great significance for ALH retrieval in the UV band. 2. In addition, given the constrained observation period in the actual multi-angle observation mode, if numerous angles focus on the same object, the target's spatial coverage or the overall number of targets will be decreased [29]. Therefore, it is necessary to find the optimal number of angles to reduce the observation time of each target while maintaining a high level of ALH information. It can be seen that, as the observation angle increases, the increase in DFS gradually decreases, but as the number of observation angles rises from 1 to 5, it basically meets the requirements of ALH retrieval (DFS \(>\) 0.5) for the main aerosol models. Even for the two aerosol types with limited polarization enhancement, C-BNM and C-BHM, the DFS is significantly improved when the observation angles increased to about 7-8. This also shows that the multi-angle observation is an effective way to improve the ALH retrieval of weak absorbing aerosol types at the UV band. 3. As the observation angle continues to increase, the DFS increase gradually slows down with the number of angles and finally converges, which means that as the number of angles continues to increase, the inversion framework constructed in this study is easily extensible. In a future study, we will add to and evaluate the potential for retrieving more aerosol properties from the UV band through the addition of multi-angle measurements.