Supplement to: Pithan, Felix; Ackerman, Andrew; Angevine, Wayne; Hartung, Kerstin; Ickes, Luisa; Kelley, Maxwell; Medeiros, Brian P; Sandu, Irina; Steeneveld, Gert-Jan; Sterk, HAM; Svensson, Gunilla; Vaillancourt, Paul A; Zadra, Ayrton (2016): Strengths and biases of models in representing the Arctic winter boundary layer - the Larcform 1 single column model intercomparison. Journal of Advances in Modeling Earth Systems, 8(3), 1345-1357, https://doi.org/10.1002/2016MS000630
Weather and climate models struggle to represent lower tropospheric temperature and moisture profiles and surface fluxes in Arctic winter, not least because they lack or misrepresent physical processes that are specific to high latitudes. The Arctic boundary layer in winter has been observed to be in either a radiatively clear or cloudy state: The radiatively clear state is characterized by strong surface radiative cooling leading to the build-up of surface-based temperature inversions, whereas the cloudy state occurs when cloud liquid water is present in the atmospheric column, allowing little or no surface radiative cooling and leading to weaker and typically elevated temperature inversions. Many large-scale models have been shown to lack the cloudy state, and some do substantially underestimate stability in the clear state. We here present results from the first Lagrangian ARCtic air FORMation experiment (Larcform 1), a GASS (Global atmospheric system studies) single-column model intercomparison which reproduces these biases of large-scale models in an idealised setup.
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