Identification of the maximum thickness of the dust layer based on CALIPSO satellite observations Case study: Khuzestan province

The main goal of this study is to identify the maximum thickness of the dust layer by using the vertical half-pipe method using CALIOP lidar data. In order to implement this method, Khuzestan province was considered as the target area. In this regard, 6 study samples that the CALIPSO satellite orbit had passed over Khuzestan province during October 2016 and 2017 were used. Based on the results of the research, the maximum thickness of the dust layer in the study samples in the completely flat and plain land in the west of the province is more than in the east. In addition, in the east of the province, the values of the maximum thickness of the dust layer mainly correspond to the lower latitudes of the region, where the ground level is lower. In general, the findings of the research show that the maximum thickness of the dust layer can be extracted from the lidar data using the airborne vertical half-track method, although the output of this method is more accurate when the dust layer has uniform and dense horizontal and vertical coverage. In addition to extracting the thickness of the dust layer, the size and density of the particles were also studied using the color ratio index. The values of this index in each of the study samples confirmed the presence of fine dust particles in the region. This index was calculated after applying the horizontal averaging method of 5 km on the redistribution data of radar waves. The 5 km horizontal averaging method has the ability to effectively reduce the noise of space lidar data and increase the accuracy of cloud detection from aerials, which reveals the border between clean and polluted air and also the knowledge of the density of aerials. Based on this, the spatial distribution of the dust layer and changes in its thickness can be seen. The results of this research can be used to predict the concentration, extent, and maximum height of the dust layer.



Based on the findings of the research, using the vertical profile method of the air force, it has the ability to extract the maximum thickness of the dust layer using spatial lidar data, although the output of this method is more accurate when the dust layer has uniform and dense horizontal and vertical coverage. In this research, in addition to extracting the thickness of the dust layer, the size and density of the particles were also studied using the color ratio index. This index was calculated after applying the horizontal averaging method of 5 km on the redistribution data of radar waves. The 5 km horizontal averaging method has the ability to effectively reduce noise in the backscattering attenuation layer and increase the accuracy of cloud detection from airborne particles, which reveals the boundary between clean and polluted air and also provides knowledge of the density of airborne particles. Based on this, the mentioned method clearly showed the density and concentration of dust particles through the distribution of lidar wave rescattering values at different heights, and the presence of dust particles in the atmosphere of the region was confirmed in all study samples. Calculating the particle size index in the atmosphere and its undeniable role in detecting dust particles is another result of this research. The values of this index in each of the studied samples in the height ranges where the thickness of the dust layer was extracted confirmed the presence of fine dust particles in the region.