Remote sensing and analysis of 2nd order, Arctic-aerosol parameters

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Aerosols are commonly defined as atmospheric particles whose size ranges from a small fraction of a micrometer to tens of micrometers. They originate from a large variety of aerosol emission processes : forest fires, wind-blown deserts, gas to particle conversion, volcanic eruptions and ocean wave processes are some of the major natural aerosol sources while fossil fuel combustion due to urban and industrial processes is the most important anthropogenic source. Aerosols can, at least as far as their optical effects are concerned, be largely divided into bi-modal, fine and coarse mode components (roughly sub and super micrometer in radius). Over the next five years, we will continue to pursue research into the characterization of bi-modal parameters such as fine and coarse mode aerosol optical depth (a parameter which is basically proportional to the column concentration of aerosols) and fine and coarse mode effective radius (average columnar radius) as a function of aerosol species. The proposed research within the context of this DG application will be focused on the higher risk extraction of refractive index information (both the real part which is an important driver of aerosol scattering properties and complex parts which is the major driver of aerosol absorption properties) from both surface and columnar optical instruments. These activities are will be subdivided into three research projects : (i) a 2-year postdoc led study on the retrieval of real and complex parts of the refractive index from surface spectral measurements and optical properties deduced from microphysical and speciation surface measurements. (ii) an optical retrieval analysis, led by a PhD student, of surface to column propagation of the fine mode refractive index findings of the pdf project (iii) a parallel coarse mode analysis (in close collaboration with the first PhD student) led by a second PhD student. Remote sensing research in the Arctic is particularly relevant in a social benefit context since this region is known to magnify climate change effects (as described in the most recent IPCC report for example). Aerosols, by virtue of their direct (scattering and absorption) effects and indirect (aerosol cloud interaction) effects are the greatest source of uncertainty in climate change dynamics (ibid). A better understanding of aerosol opto-physical parameters, notably intensive parameters such as average size and refractive index will help to calibrate and improve the aerosol dynamics packages of Arctic-aerosol models and accordingly lead to important consequences in terms of radiative forcing and climate models of the Arctic.