Remote sensing of Arctic aerosols: analysis of intensive parameters

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Aerosols are atmospheric particles whose size ranges from a small fraction of a micrometer (1/ 1000000 of a meter) to tens of micrometers. They can exhibit large (extensive) variations in concentration and significant (intensive) variations in their size, shape and chemical composition. Ground-based sunphotometry is the predominant technique for measuring average aerosol effects; one tracks the sun all day and measures the attenuation caused by the aerosols between the instrument and the sun. Aerosols (notably fine, sub-micron aerosols) have significant health impacts during pollution events. Their effect on radiation as well as on cloud properties represent important climate change factors. Climatic changes in the Arctic are more severe than in southern regions and aerosols play a major role in contributing to these changes. It is accordingly important that the physical properties of aerosols and Arctic aerosols in particular be well understood. My long term objective is to better understand aerosol behavior in terms of measurable optical variations. The significance, for example, of some specific aerosol optical depth (AOD) spectral shape, a change in the angular variation of sky radiance, or variations in lidar (pulsed laser) measurements of aerosol altitude properties, cannot be understood until one has a grasp of the essential environmental and instrumental physics influencing the measurement. This objective is advantageously accompanied by projects involving the evaluation of aerosol dynamics models using optical data; our experience has been that the process of model evaluation inevitably enhances one's physical understanding of both the aerosol phenomena which the model purports to simulate and the measurements themselves. The short term objective of the research proposal is to better understand the measurable physics of second order (intensive) aerosol optical parameters. This specifically means the employment of spectral techniques to extract fine and coarse mode effective radius values and the extraction of single scattering albedo (sensitive to aerosol absorption).