Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Investigations on trace gases and its inter comparison with near surface aerosols along with satellite and model observations over semi arid region india

Auteur : Lingaswamy, Pedda A

Université de soutenance : Sri Krishnadevaraya University

Grade : Doctor of Philosophy (PhD) 2014

Préface partielle
The concentrations of trace gases are low in the atmosphere, but they play a crucial role in determining the ambient air quality over India. Trace gas chemistry can adapt radiative transfer by which it can affect the climate. Ozone (O3,) produced in the troposphere plays a vital role in the radiative and chemical processes of the atmosphere due to its strong oxidizing capability. Ozone is an important precursor of hydroxyl radical that decides life time of trace gases species and acts as a major role in the lower atmospheric chemistry. Two mechanisms have been proposed to account for the enhanced rural O3. One is the transport of its precursors like oxides of nitrogen (NOX), carbon monoxide (CO), non-methyl hydrocarbons (NMHCs) followed by the photo chemical ozone production and another is transport of O3 from urban areas to the downwind sites. Nitrogen oxide (NO) and nitrogen dioxide (NO2) enter the atmosphere from natural (lightning and biological) processes and pollutant sources. The degradation of ozone reduction is due to the diminishing of solar radiation, affects the photo chemical activity and dynamical process in the atmosphere. Photo chemical production is nonlinearly dependent on the levels of precursors. Depending upon the precursor’s strength and photochemical reactions, tropospheric ozone varies spatially and temporally over the globe. The photo chemical ozone production in urban areas rises with NOX but is less sensitive to volatile organic carbons (VOCs) emissions ; in contrast to this in rural areas ozone production is appears to be more sensitive to VOCs emissions. In city areas, the concentration of O3 is usually lower compared to the sub urban areas. This is mainly because of higher titration process between NO and O3. Meteorological factors are also responsible for the variation of O3 in the ambient air.

Mots clés : investigations on trace gases aerosols

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