## 1 Introduction  
Atmospheric aerosols are characterized as solid and liquid suspended particles, forming a relatively unstable suspension system in the atmosphere [1; 2; 3]. Aerosol particles range in size across five orders of magnitude, from 0.001-100 \(\upmu\)m, and exhibit complex and diverse morphologies [4; 5]. Aerosols affect the formation and distribution of clouds in the atmosphere by scattering and absorbing solar radiation, thus directly affecting the energy balance of climate [6; 7; 8] Apart from their impact on the climate, aerosols also significantly impact the air quality and human health, as they can contribute to the production of photochemical smog, haze, and acid rain. Prolonged exposure to adverse atmospheric conditions with excessive concentration of aerosols (especially particulate matter PM\({}_{2.5}\) particles) increases the risk of the development of lung and respiratory diseases [9; 10; 11; 12]. The aerosol distribution strongly varies in time and space, while the mechanism of their climate effects is complex and uncertain, thus necessitating studies on the variability of aerosol optical and physical properties [1; 13; 14; 15; 16]. Therefore, long-term observations and analysis of aerosols are the key tools for a comprehensive understanding of aerosol characteristics [17; 18; 19; 20]. Concurrently, they can deepen scientific understanding of aerosol environmental effects and may help provide theoretical support for the institutions and agencies to aid the introduction of environmental protection policies. Presently, data on aerosol optical properties are mainly retrieved through ground measurements and satellite observations. Ground measurements are mostly performed through a solar photometer network, such as the Global Aerosol Sun Photometer Monitoring Network (AERONET) established by NASA providing global aerosol observation data, and the ground-based aerosol observation network established by China (CARSNET) providing aerosol observation data in China. The scientific community has published a plethora of studies on the basic characteristics of aerosols whose data have been retrieved using high-resolution sun photometer-based observations from AERONET and CARSNET [21; 22; 23; 24; 25; 26]. However, due to the limited number of ground measurement sites, data on the large-scale aerosol distribution characteristics cannot be obtained. Satellite observations can alleviate the deficiency of ground observations by providing larger spatial coverage of aerosol data. These datasets help establish a basis for studying aerosol optical properties at a global scale. For instance, the high-frequency moderate resolution imaging spectroradiometer (MODIS) carried by the Terra and Aqua satellites launched by NASA has enabled the monitoring of global aerosol optical properties [13; 22; 27]. Although satellites have many advantages over ground stations, the accuracy of satellite data is slightly lower than that of ground stations [10; 26; 28]. NASA also launched the active remote sensing instrument on-orbit initiated Cloud-Aerosol Light Detection And Ranging and Infrared Pathfinder Satellite Observation (CALIPSO) mission initiated in 2006 [20]. The Cloud-Aerosol Lidar with orthogonal polarization (CALIOP) consists of an active optical remote sensing sensor with a dual-wavelength polarization channel. CALIOP is used to continuously monitor aerosols with high spatio-temporal resolution and to provide a high-resolution vertical profile of aerosol properties. Overall, CALIOP is used to obtain the three-dimensional spatial and temporal information of the vertical distribution of aerosols, along with their optical and microphysical characteristics [16; 29; 30; 31]. It is essential to study the large-scale three-dimensional distribution of physical and aerosol optical properties to quantify the aerosols' direct and indirect effects. In Saudi Arabia, economic and industrial development has led to an increase in anthropogenic emissions and has enhanced the aerosol concentration [32].