Cloud microphysics in Arctic and Antarctic environments derived from infrared emission spectroscopy

Climate models struggle to accurately represent polar regions, particularly during polar night, when cloud cover is especially prevalent. The uncertainty budget is dominated by cloud and cloud-aerosol interactions, but the difficulty in maintaining robust field observations means a lack of long-term validation datasets for key cloud parameters. Long-term measurements of the downwelling thermal infrared (400 - 3000 cm-1) have been recorded since 2008 with an Atmosphere Emitted Radiance Interferometer (AERI) at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut, Canada (80°N, 86°W) and operated by the Canadian Network for the Detection of Atmospheric Change (CANDAC), while a similar instrument was deployed at McMurdo Station for 2016 as part of the ARM [Atmosphere Radiation Measurement] West Antarctic Radiation Experiment (AWARE) program. We analyse the downwelling infrared emission of the polar atmosphere recorded by these AERI instruments, with supplementary data from observations and models, to derive a climatology of microphysical and optical properties of clouds at Eureka (since 2008) and McMurdo (2016), including optical depth, thermodynamic phase, and liquid droplet and ice crystal effective scattering radii. A comparison of these Arctic and Antarctic cloud properties reveals an abundance of cloud morphological states at these two polar locations. This presentation will also describe the temperature dependence of cloud microphysics, seasonality in the timeseries, and the effect of inversions on cloud boundaries, as well as challenges in performing these retrievals.