Case Investigation on the Influence of In-Snow Particles' Size and Composition on the Snow Light Absorption and Albedo

The snow physical parameters are closely related to the sizes, shapes, and chemical composition of light-absorbing particles (LAPs). By utilizing a computer-controlled scanning electron microscope software called IntelliSEM-EPAS (TM), we first report the measured size-resolved concentration of soot, dust, and fly ash particles in fresh (wet) and aged (dry deposition) snow samples collected at an industrial city in China during and after a snowfall at intervals of 6-8 days. Due to wet scavenging by seasonal snow, soot and dust particles in snow are absorbed by 69.7% and 30.3% at wavelengths of 550 nm, lowering snow albedo by 0.0089 and 0.0039, respectively. Soot particle size increases slightly during dry deposition, whereas size-resolved mineral dust does not undergo a significant shift in particle size. These results indicate the essentiality to involve the effects of accurate size and composition of in-snow LAPs for a better assessment of snow light absorption and reflectance. Plain Language Summary A field survey was undertaken to collect freshly fallen (1) and aged surface (15) snow samples at 1-day intervals in the center of Changchun city, China, which is surrounded by heavy industrial emission sources. We used an advanced computer-controlled scanning electron microscope to determine particle size and number distributions of three major light-absorbing particle types with diameters of 0.2-10 mu m in seasonal snow, namely soot, dust, and fly ash. Soot and dust particles deposited in various ice-grain sizes via wet and dry deposition were also examined in terms of their contributions to light absorption and snow albedo reduction. We report here a first attempt to detect a combination of log-normal soot, dust, and fly ash in seasonal snow, as well as their potential effects on the reduction of snow albedo.

Automated summary

Using a computer-controlled scanning electron microscope software called IntelliSEM-EPAS (TM), we measured the size-resolved concentration of soot, dust, and fly ash particles in fresh and aged snow samples collected in an industrial city in China. Wet scavenging by snow was found to absorb 69.7% and 30.3% of soot and dust particles at a 550 nm wavelength, respectively, leading to a decrease in snow albedo. The size of soot particles increased slightly during dry deposition, while mineral dust particles did not show significant changes in size.