The dust event was selected because it coincided with ground-based lidar observations collected at Shiraz University during the early operational period of the system, giving the team a vertical profile of the atmosphere over the city at the moment pollution concentrations spiked. Model-based concentration data captured the severity of the episode. CAMS-derived PM10 concentrations rose to 94 micrograms per cubic meter, and PM2.5 reached 70.3 micrograms per cubic meter, at 00:00 UTC on 6 July 2006.

To classify what was floating overhead, the team applied the one-step POLIPHON method, a retrieval technique that separates aerosol types and estimates the mass concentration corresponding to each type. Both the lidar retrieval and the satellite record pointed in the same direction: mineral dust dominated the aerosol column over Shiraz during the event. The satellite perspective came from CALIOP, the lidar aboard the CALIPSO satellite, which profiles aerosols from orbit, and from MODIS observations.

Together with the ground-based lidar, these observations revealed a dust-dominated aerosol layer over the city, allowing the researchers to examine how the pollution was stacked vertically rather than merely how thick it appeared from the surface. A key diagnostic was optical. The layer-integrated particulate depolarization ratio, measured at the 532-nanometer wavelength, came in at approximately 0.23.

This optical fingerprint, combined with the POLIPHON retrieval, established mineral dust as the dominant component of the layer. Where did the dust come from? HYSPLIT trajectory modeling traced the paths air parcels took before arriving over Shiraz, while ECMWF reanalysis data supplied the wind patterns responsible for dispersing the aerosols.

The combined analysis suggested regional transport, with possible contributions from dust-active regions in Mesopotamia and southeastern Iraq, alongside local or regional dust uplift within Fars Province, the province that contains Shiraz. That dual origin matters for interpretation. The study's findings indicate that both mechanisms plausibly contributed to the 6 July 2006 episode, producing the complex vertical pollution structure that motivated the analysis.

Beyond the single case, the researchers highlight the methodological value of the approach.

Subject of Research: Vertical distribution and transport of mineral dust aerosols over Shiraz, Iran, analyzed with ground-based lidar, satellite observations and atmospheric models

Article Title: Synergistic use of satellite and ground-based lidar observations to analyze the vertical distribution of atmospheric pollution over Shiraz, Iran

Article References: Razavi, K., Nadgaran, H., & Bayat, F. (2026). Synergistic use of satellite and ground-based lidar observations to analyze the vertical distribution of atmospheric pollution over Shiraz, Iran. Air Quality, Atmosphere & Health, 19(11), Article 245. https://doi.org/10.1007/s11869-026-02136-9

Image Credits: AI Generated

DOI: 10.1007/s11869-026-02136-9

Keywords: atmospheric aerosols, mineral dust, lidar, CALIPSO, MODIS, HYSPLIT, POLIPHON, air quality, Shiraz, Iran, PM10, PM2.5