Microphysical and Compositional Differences between Saharan and Middle Eastern Dust Revealed by UAS Observations

Abstract

The rising frequency of mineral dust events in the eastern Mediterranean underscores the need for high-resolution observations to better characterize their properties and impacts. This study reports results from the Cyprus Fall Campaign 2021, which aimed to test and validate a new cost-effective methodology for quantitative dust measurements using Giant Particle Collector(GPaC), Portable Optical Particle Spectrometer(POPS), and Universal Cloud and Aerosol Sounding System(UCASS) sensors on-board Uncrewed Aerial Systems(UAS). The Cyprus Fall Campaign 2021 captured the microphysical characteristics of dust particles from two major global sources: North Africa (NA) and the Middle East (ME). The campaign was conducted from 18 October to 18 November 2021 and comprised 36 UAS flights. This work represents the first intensive UAS-based dust characterization campaign in Cyprus and the wider Mediterranean region during the autumn season. Remote-sensing and back-trajectory analyses revealed NA dust layers up to 7kma.s.l. (above sea level) over Cyprus, compared to 3.8km for ME dust. Impactor sampling demonstrated a near-1 collection efficiency for particles between 4-14μm, highlighting its effectiveness onboard the UAS. Particle volume size distributions showed a fine-mode peak at 0.25μm in both cases, and distinct coarse-mode peaks at 2.2 and 4.8μm for NA and ME dust, respectively. High-altitude impactor samples showed two distinct dust signatures: NA dust enriched in kaolinite-like and Ca-bearing phases, and ME dust dominated by illite/muscovite and Fe-rich components, indicating contrasting source characteristics influenced by granulometry, transport, and atmospheric processing. This study showcases the capability of high-resolution UAS sampling to characterize atmospheric dust and improve understanding of its regional and climatic impacts.