Development and Applications of Far Infrared Radiometry in Cold Atmospheres

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The general aim of my research and for this proposal is to investigate the indirect effects of anthropogenic emission in the form of aerosols and precursor gases on the atmospheric water cycle at high latitudes. Central to this study is the observation of optically Thin Ice Clouds (TIC) and light precipitation (diamond dust), accounting for nearly 50% of the annual precipitation in the Arctic. Yet many of the occurrence of TIC are misreported as clear sky, since a ground observer sees stars during the polar night. Still, frequent light precipitations are reported as "trace", without a quantitative evaluation. As a result, TIC processes are still poorly represented in atmospheric models, leading to forecasting errors. It is now recognized that man-made aerosols can alter cloud and precipitation. The originality of my research is to fill an existing gap in cloud and light precipitation observation at high latitudes using a highly innovative method in the far infrared (FIR). These clouds, sensitive to aerosols via ice nucleation, can significantly modulate the amount of FIR (8-50µm) radiation escaping the Earth and affecting temperatures in the upper to mid troposphere and at the surface. Since FIR signature of clouds is very sensitive to their properties (crystals size and shape) and optical depth, these quantities can also be retrieved from ground-based and satellite observations. In this discovery program, theoretical calculations and measurements are used to show how the atmospheric far IR will provide valuable information for weather forecasting, data assimilation and climate simulations, about its water vapour content, the microphysical characteristics of ice clouds and common light precipitation. In this context, I am leading the "Thin Ice Clouds in the Far InfraRed Experiment" (TICFIRE) as a forthcoming satellite mission at the Canadian Space Agency (CSA). Endorsed by the Year of Polar Prediction program (YOPP, 2017-22), a World Meteorological Organisation initiative, in collaboration with the Canadian Space Agency (CSA) and Environment Canada (ECCC), with other universities and the industry (INO, LR Tech, Honeywell), I am leading new measurements in the mid and far IR range to advance our knowledge of TIC Polar clouds. This fall (2018), we have deployed the new Far IR Radiometer (FIRR-2), base on an innovative Canadian technology. The FIRR is a prototype for the future TICFIRE satellite and for a new ground-based instrument aimed to improve monitoring and weather prediction in Polar Regions. Under YOPP program, I am conducting innovative experiments and extended data analysis leading to operational applications of the FIRR and to study TIC microphysics and radiation interaction. Central to these measurements is the ability to evaluate accurately the size of ice crystals, here, my recent results have shown that for cold polar clouds and cirrus, the FIRR can outperform and complement other technologies.