## 5 Results of Aerosol Model and the Optical Properties Inter-Comparison
### Inter-Comparison of Aerosol Properties between CE318 and the VIIRS_EDR  
Since the M_VIIRS_EDR performs less well in the NCP region based on above analysis and M_VIIRS_ML is defined according to the CE318 inversion in local regions, we only compare the aerosol properties between CE318 and the VIIRS_EDR. Table 6 shows the averages of the SSA40 nm of fine, coarse and bi-modal aerosols derived from CE318 (AOD40 nm \(>\) 0.4) and the VIIRS_EDR (AOD50 nm \(>\) 0.25) at the three sites over the time period of evaluation (2 May 2012-31 March 2014). The values of SSA440 nm from the CE318 are less than that of the VIIRS_EDR for all modes and all sites, which indicates that VIIRS_EDR overestimates SSA40 nm values over all sites (consistent with SSA670 nm in Table 5). The difference of SSA440 nm in the coarse mode (i.e., 0.09 in Beijing, 0.12 in XiangHe, and 0.06 in Xinglong) is larger than SSA440 nm in fine mode (i.e., 0.02 in Beijing, 0.04 in XiangHe and 0.03 in Xinglong). This indicates that aerosol properties in the coarse mode in the VIIRS_EDR need to be revised for the NCP region. The biases of bi-mode SSA440 nm are 0.03 (Beijing), 0.05 (XiangHe) and 0.03 (Xinglong). The overestimation of SSA but largest positive AOD MB of the VIIRS_EDR over Beijing site indicate again that other positive bias factor (e.g. surface reflectance characterization) overpowersthe negative bias due to SSA of aerosol model type over Beijing. The largest overestimation of SSA and negative MB of AOD (in Table 3) are occurred at XiangHe, which may indicate that errors from the aerosol model type are overpowering at the XiangHe site. Since the SSA is calculated by inputting the aerosol parameters in Table 2 from [PERSON] et al. [6] to the Mie scattering code and large differences of SSA between the VIIRS_EDR and CE318 are found above, it is necessary to compare the aerosol properties between the VIIRS_EDR and CE318. The constraints of CE318 AOD\({}_{440 nm}>0.4\) and VIIRS_EDR AOD\({}_{550 nm}>0.25\) are also used and the daily aerosol optical properties retrieved from CE318 sky radiance measurements are averaged before the followed analysis. Table 7 shows the average aerosol physical properties from CE318 and the VIIRS_EDR. The refractive index is RI with real part is RI(r), while imaginary part is RI(i). Volume mean radius, standard deviation and volume concentration are r, \(\sigma\) and V, respectively. The fine and coarse mode aerosols are shown by f and c in bracket pairs. Figure 4 shows the seasonal comparison of normalized aerosol physical properties from CE318 and the VIIRS_EDR at the three sites. Each parameter is normalized between 0.1 and 1 to well show the difference of CE318 and the VIIRS_EDR. The length of each radius in the circle equals 1 and each radius direction stands for one aerosol parameter. Distinctly differences of various parameters between CE318 and the VIIRS_EDR can be found. For the total averages in three sites (Table 7), CE318 shows high values of RI(r) 1.47-1.49 and RI(i) 0.0083-0.013, which indicates that aerosol in the NCP is more absorptive than that used in the VIIRS_EDR, which corresponds the overestimation of SSA for the VIIRS_EDR (Table 5). The r(f) values from CE318 (0.19-0.22) are slightly higher than the values of the VIIRS_EDR (0.18-0.19), while the r(c) values of CE318 (2.70-2.84) are significantly lower than the values of the VIIRS_EDR (3.15-3.51), which may cause more dust aerosol for the VIIRS_EDR (Figure 2) and also reflects the dust aerosol model in Cape Verde maybe different from the dust in Asia [40; 41]. The \(\sigma\)(f) in CE318 is higher than the