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Accueil du site → Doctorat → États-Unis → 2021 → Sources and Impacts of Aerosols in the Atmosphere : Case Studies of Dust and Biomass Burning Pollution

University of Arizona (2021)

Sources and Impacts of Aerosols in the Atmosphere : Case Studies of Dust and Biomass Burning Pollution

Hossein Mardi, Ali

Titre : Sources and Impacts of Aerosols in the Atmosphere : Case Studies of Dust and Biomass Burning Pollution

Auteur : Hossein Mardi, Ali

Université de soutenance : University of Arizona

Grade : Doctor of Philosophy (PhD) 2021

Biomass burning emissions and airborne aeolian dust are two major components of atmospheric aerosols. Numerous research have been done to characterize the spatial and temporal patterns observed in the emission and travel of these aerosols worldwide. The study of aerosols has become increasingly important owing to climatic changes driven by global warming. The overall impact appears as longer periods of drought and heat. These conditions can lead to more extensive periods of dust and biomass burning emission as it is favorable both for the formation of aeolian dust sediments and wildfire incidents. In the first part of the present study, the impact from the desiccation of a large hypersaline lake is studied on aeolian dust pollution in neighboring regions of the lake. These analyses are done for a time period spanning from before the desiccation of the lake to periods after it. Analysis of satellite retrieved aerosol optical depth (AOD) demonstrates that the observed seasonal and interannual patterns are mainly driven by the emissions from large aeolian deposits in the neighboring countries, upwind the area of study. however, the same set of results that contributed to the desiccation of the lake can lead to more numerous and extensive dust seasons in the upwind areas. In the following chapters, biomass burning emissions are studied via different sets of analyses. At first, microphysical and chemical characteristics of biomass burning plumes from two major wildfire incidents near the coast of California are studied via a set of airborne probes. From a macrophysical perspective, a statistic review of the smoke plume is provided for parameters such as plume thickness, number of layers, and relative positioning of smoke layer and the residing stratocumulus cloud deck in that region. By simulating the heating rate impact from the biomass burning plume, an enhancement in vertical heating rates is observed. Results show this enhancement is stronger when a stratocumulus cloud layer resides beneath the biomass burning layer. On a separate project, biomass burning impact on cloud microphysical properties is studied through analysis of the connection between cloud droplet number concentration and effective radius with aerosol number concentration above and below the cloud. Our results demonstrate that cloud microphysical characteristics are most sensitive to aerosol properties at cloud base, rather than cloud top, where the majority of biomass burning aerosols reside. Laboratory composition analysis of cloud water samples collected from biomass burning impacted clouds reveal an impact from crustal species, carried away by biomass burning plumes. This impact is most evident for clouds impacted by plumes of smoke close to the source of fire.


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