An Investigation of Dust Activities in Southwest Baluchestan, Iran, by Synergistic use of Handheld Sunphotometer Measurements and CALIPSO-CALIOP Data

Abstract

The atmospheric aerosol properties near Iranshahr City in Southwest Baluchestan, Iran, were investigated using handheld Calitoo sunphotometer measurements, space-borne CALIPSO-CALIOP lidar recordings, and synoptic station data. The findings indicate the prevalence of dust aerosols throughout the year, with a pronounced presence during the summer season. The aerosol optical depth (AOD), as determined by Calitoo measurements at 540 nm between April and October 2022, peaked in July with a monthly-mean value of 0.61 ± 0.14. During this month, the Angstrom exponent reached 0.43 ± 0.19, providing further evidence of severe dust storm activities in the region. An analysis of the level 2 aerosol profile data obtained from CALIOP measurements during 2006-2023 has been presented. The monthly-averaged AOD at 532 nm obtained from CALIOP data has a bell-shaped distribution with a peak in July (0.92 ± 0.39). These results are in agreement with those measured by Calitoo. The vertical profile of the particulate depolarization ratio (PDR) at 532 nm confirms the dominance of dust at all altitudes. Moreover, the extinction coefficient spike near the surface explains why horizontal visibility decreases during dust events. Consistent with previous studies, our findings identify the dry bed of Hamun Lakes as the primary dust source for the Baluchestan region. Additionally, the dry bed of the Jazmurian ephemeral lake and parts of the Lut Desert appear to be other major dust sources, particularly affecting the western parts of Baluchestan, Iran. These latter sources should be studied in more detail.