Temporal evolution of dust in the atmosphere of Baluchestan, southeast Iran, studied by handheld sun-photometer, space-borne lidar, and synoptic data

Abstract

The atmospheric aerosol parameters in the vicinity of Iranshahr County in Baluchestan, located in the southeast of Iran (27.00-27.40 °N, 60.09-61.09 °E), were investigated using a Calitoo handheld sunphotometer, space-borne CALIOP-CALIPSO lidar, and synoptic station measurements. 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 maximum value of 0.63 ± 0.20. During this month, the Angstrom exponent reached the value of 0.44 ± 0.21, providing further evidence of severe dust storm activities in the region. An analysis of the level 2 aerosol profile data obtained from CALIOP measurements spanning a decade (2013-2022) has been presented. The results derived from the vertical profiles of extinction coefficient, depolarization ratio, and AODs are consistent with those measured by Calitoo. The monthly-averaged AOD at 532 nm exhibited its maximum and minimum values in July and January, registering at 0.83 ± 0.36 and 0.09 ± 0.13, respectively. As indicated by prior research, the primary atmospheric system responsible for dust events in the area is the north and northwesterly “120-days” or the Levar wind. Synoptic measurements of horizontal visibility indicated a significant reduction during the Levar wind period, which extends from April to late August.