CALIOP-Based Evaluation of Dust Emissions and Long-Range Transport of the Dust from the Aral-Caspian Arid Region by 3D-Source Potential Impact (3D-SPI) Method.

The average monthly profiles of the dust extinction coefficient (epsilon) were analyzed according to the CALIOP lidar data from 2006-2021 for 24 cells (size of 2 degrees x 5 degrees) in the Aral-Caspian arid region (ACAR; 38-48 degrees N, 50-70 degrees E). Using the NOAA HYSPLIT_4 trajectory model and the NCEP GDAS1 gridded (resolution of 1 degrees x 1 degrees) archive of meteorological data, the array of >1 million 10-day forward trajectories (FTs) of air particles that started from the centers of the ACAR cells was calculated. On the basis of the FT array, the average seasonal heights of the mixed layer (ML) for the ACAR cells were reconstructed. Estimates of the average seasonal dust optical depth (DOD) were obtained for ACAR's lower troposphere, for ACAR's ML ("dust emission layer" (EL)), and for the lower troposphere above the ML ("dust transit layer" (TL)) above each of the ACAR cells. Using the example of ACAR, it is shown that the analysis of DOD for the EL, TL and the surface layer (SL; the first 200 m AGL) makes it possible to identify dusty surfaces that are not detected on DOD diagrams for the entire atmospheric column, as well as regions where the regular transport of aged dust from remote sources can generate false sources. Based on FT array, the fields of the potential contribution of both the ACAR's dust transit and the ACAR's dust emission layers as well as of the entire ACAR's lower troposphere into the DOD of the surrounding and remote regions are retrieved using the original method of potential impact of a three-dimensional source (3D-PSI). It has been found out that ACAR dust spreads over almost the entire Northern Hemisphere; the south and southeast regions of the ACAR are subject to the maximum impact of the ACAR dust. Quantitative estimates of the potential contribution of ACAR dust to the regional DODs are given for a number of control sites in the Northern Hemisphere. The results could be useful for climatological studies.