The Detection of Desert Aerosol Incorporating Coherent Doppler Wind Lidar and Rayleigh-Mie-Raman Lidar  
[PERSON]  
1 School of Earth and Space Science, University of Science and Technology of China, Hefei 230026, China; 1 [EMAIL_ADDRESS] (M.L.); [EMAIL_ADDRESS] (L.S.)  
[PERSON]  
1 School of Earth and Space Science, University of Science and Technology of China, Hefei 230026, China; 1 [EMAIL_ADDRESS] (M.L.); [EMAIL_ADDRESS] (L.S.)  
[PERSON]  
1 School of Earth and Space Science, University of Science and Technology of China, Hefei 230026, China; 1 [EMAIL_ADDRESS] (M.L.); [EMAIL_ADDRESS] (L.S.)  
[PERSON]  
2 School of Atmospheric Physics, Nanjing University of Information Science and Technology, Nanjing 210044, China; hanhaho  
With the Doppler wind lidar technique, one of the most important indicators in the observation of atmospheric vertical exchange processes, that is, the accurate measurements of the vertical wind component, can be obtained. Using the combination of Doppler wind lidar and other types of aerosol lidars, accurate aerosol backscatter signals and wind profiles were obtained simultaneously [13]. There is no doubt that the combination of several lidars would make it more accurate, but it also increases the cost and volume, making it less conducive to airborne and spaceborne detection. Recently, many studies have been devoted to calibrating the backscatter of coherent Doppler wind lidar (CDWL) to obtain the profiles of aerosols and wind with only one lidar. To accurately retrieve the extinction coefficient of aerosol using CDWL, the effect of heterodyne efficiency needs to be considered [25; 26], which represents the coupling of the mode field of the local oscillator and backscatter light. To quantify the aerosol transport and change in aerosol properties from the Sahara desert to the Caribbean, backscatter and extinction coefficient profiles were retrieved from airborne CDWL using function fitting of heterodyne efficiency, measured by changing the altitude of the aircraft [27]. Normalized backscatter power data points from horizontal detection were used to fit heterodyne efficiency, and the results of aerosol optical depth were calibrated with other devices, including a sun photometer [28], ceilometers [29], and atmospheric visibility [30]. Moreover, theoretical focus function and calibration based on liquid clouds were also adopted in the retrieval of aerosol [31; 32; 33].  
Comparison and calibration are usually performed on the aerosol optical depth (AOD), due to the lack of high accuracy and resolution of the reference devices. In this work, an experimental comparison between the aerosol extinction profiles using CDWL and Rayleigh-Mie-Raman lidar (RMRL) was achieved. By applying the heterodyne efficiency from horizontal measurement, the backscatter profiles of CDWL were calibrated and used to retrieve the aerosol extinction coefficient. To compare the results of the two lidars, a data assimilation and comparison method is proposed, and the data from the Raman lidar are involved to improve the accuracy of the results. A consistency analysis of the results was conducted, and good agreement with the determination coefficients of 0.90 and 0.89 was found.  
The paper is organized as follows. The involved lidar systems are described in Section 2, and Section 3 introduces the retrieval and comparison methods. To focus on the detection of aerosol optical properties, the retrieval of wind speed will not be discussed in this work. Section 4 introduces the comparison results during a 5-day vertical desert aerosol observation. Finally, Section 5 summarizes the conclusion and the outlook of future studies.