## 6 Conclusions  
In this paper, we used the extended ultraviolet band (388 nm) to simulate multi-angle polarization synthetic data and fully evaluate the performance of multi-angle polarization measurements in the UV channel for passive remote sensing of the aerosol layer heights of ten typical aerosol model types used in the Chinese region. The research results show that  
1. The extended ultraviolet 388 nm band is an important information source for passive remote sensing ALH retrieval. With additional constraints, such as the aerosol single scattering albedo and AOD from independent sources (thought to be obtained by retrieval from other channels), MAPMU can theoretically retrieve ALH under different conditions by combining polarization measurements with multi-angle measurements. 2. Polarization measurements have important impacts on ALH retrieval at the UV band, but the improvement is different for each typical aerosol model due to their different optical properties. For example, the reduction in posterior uncertainties of ALH retrieval is 6-39% for the fine mode aerosol types following the addition of polarization measurements. However, the improvement for coarse mode aerosol types is relatively small, especially for C-BHM and C-BNM which characterize the types of dust found in North China and have larger median radii and low absorption rates in the UV band. The retrieved reduction of posterior uncertainties is only 1-8%. 3. Compared with single-angle polarization observations, which have difficulty retrieving the ALH for coarse mode aerosol types, the multi-angle observation mode effectively improves the DFS of ALH retrieval. In particular, for the ALH retrieval of C-BHM and C-BNM, the combination of polarization and multi-angle measurements could be used to improve the aerosol layer height information. When the number of viewing angles is increased to 6, the DFS increment is above 0.4, on average, for different aerosol types. 4. The predefined model errors include the error of the total aerosol volume and the effective radius and the imaginary part of the complex refractive index as well as the error of the surface reflectivity \(\rho_{s}\) and the \(k_{1}\) parameter, which will lead to the largest change in the DFS of ALH retrieval. The effect of other parameter errors on the aerosol and surface models is relatively small. In summary, the addition of polarization and multi-angle measurements can effectively improve ALH retrieval compared with single-angle intensity measurements in the UV band. For ALH retrieval under coarse-mode aerosol types, in addition to considering the polarization channel, multi-angle observations also need to be considered. We suggest that the number of viewing angles should be 5-6 to achieve a good level of performance (DFS \(>\) 0.5) for ALH retrieval in the UV band for the typical aerosol model types. Additionally, reducing the retrieval errors of these key parameters, as presented above, will effectively improve the uncertainty associated with ALH retrieval in the UV band. Conceptualization, Y.Z., Z.L. ([PERSON]) and [PERSON]; Formal analysis, [PERSON], [PERSON] ([PERSON]), [PERSON] and C.F. ; Methodology, [PERSON], [PERSON] ([PERSON]), [PERSON] and C.F. ; Supervision, C.F. and Z.L. ([PERSON]); Visualization, [PERSON], [PERSON], [PERSON] and L.Z. ([PERSON]); Writing--original draft, H.G. ; Writing--review and editing, H.G., C.F. and H.X. All authors have read and agreed to the published version of the manuscript. This study was supported by the National Natural Science Foundation of China (Grant No. 41871269), the Major Projects of High Resolution Earth Observation Systems of National Science and Technology (05-Y30B01-9001-19/20-3), the National Outstanding Youth Foundation of China (Grant No. 41925019), and the Space Pre-research Projects (No. D010206). Not applicable.