## 4 Experiments and Results  
Field joint experiments with the CDWL and RMRL were conducted from 16 to 21 February 2023. The Raman lidar only works from 22:00 to 6:00 local time, so only the data during the nighttime were compared. Figure 5 depicts the backscatter profiles averaged over ten minutes altitude during the nighttime and daytime. Both the CDWL and RMRL demonstrate a vertical detection capability of more than 3 km during the nighttime, and it can be seen that the aerosols are mainly distributed at altitudes below 3 km. The backscatter signal at 386 nm decays smoothly because the Raman backscatter coefficient is proportional to the density of nitrogen, which is independent of the aerosol profiles. During the daytime, the Raman lidar is turned off, and the effective detection ranges of the other lidars are also reduced. With the method in Figure 4, the extinction coefficients at various wavelengths were retrieved with the resolution of 30 m/1 min, as shown in Figure 6, which also can be used to retrieve the color ratio. Only the results from 22:00 to 6:00 local time are plotted. Figure 6d, e shows the extinction coefficients at 1548 nm using the data from the RMRL and CDWL, respectively, and the comparison results show good consistency. It can be noticed that longitudinal stripes appear in Figure 6, which may mean the internal gravity waves strongly affect the backscatter, particularly at 0:00 on 20 February. To compare the retrieval of extinction coefficients with the two lidars in detail, the results within a height range at the same time are displayed, as shown in Figure 7. It needs to be mentioned that the results vary greatly in the near field (mainly in altitudes ranging below 0.5 km). The signal of the RMRL is uncalibrated in the range of 0-0.5 km due to the lack of a stable overlap factor, while the CDWL is calibrated with a relatively stable heterodyne efficiency. Inconsistent results appear at 6:00 local time on 18 February, the  
Figure 4: Overview of the data processing procedure. CDWL, coherent Doppler wind lidar; DC, direct current. output power of the laser in the RMRL decreases, and the effective detection distance is reduced. Consequently, the measurement of the RMRL shows poor ability in aerosol retrieval, causing a large difference between the CDWL and RMRL. Figure 5: Ten minutes averaged altitude profiles of backscattered signals measured at **(a)** 0:00 and **(b)** 12:00 local time on 20 February. The Raman lidar does not work during the daytime. The legend indicates the wavelengths of the backscatter signals in nanometers. Figure 6: Results of extinction coefficients at the wavelengths of **(a)** 355 nm; **(b)** 532 nm; **(c)** 1064 nm; **(d)** 1548 nm using the RMRL; **(e)** and 1548 nm using the CDWL. The results from 22:00 to 6:00 local time on the 16, 17, 18, 19, and 20 February are displayed when the Raman lidar works routinely. The time resolution and height resolution are 1 min and 30 m, respectively. The scatter diagrams of the aerosol extinction coefficients retrieved from the CDWL and RMRL are shown in Figure 8. The results of the CDWL are plotted versus those of the RMRL, and the density of the data points is normalized and displayed in different colors. Moreover, the distributions of the bias are inserted in the bottom right corner of each panel, in which the negative bias means that the results of the CDWL are lower than that of the RMRL. In addition, due to the effects of different overlap factors, comparisons using data ranging from 0.5 to 3 km and from 0 to 0.5 km are divided into two groups. The first-order linear fitting functions of the results, the determination coefficients R, and the root-mean-square error (RMSE) are added to the upper left corner of each graph. Good performance with an R of 0.90 and 0.89 was obtained, proving the accuracy of aerosol retrieval by coherent detection after heterodyne efficiency correction. In contrast, results ranging from 0 to 0.5 km are shown in Figure 8c.d.