Evaluating Arctic meteorology modelled with the Unified Model and Integrated Forecasting System

Abstract

<p>State-of-the-art numerical models such as the UK Met Office Unified Model and European Centre for Medium-Range Weather Forecasting Integrated Forecasting System are crucial tools for forecasting future Arctic warming. However, their ability to reproduce clouds and boundary layer meteorology in the high Arctic has not been thoroughly evaluated following significant model developments over the last 10 years. Model evaluation is key to understanding where remaining process weaknesses lie, thus informing further parametrization developments to improve the simulated surface energy budget.</p><p>Here, we evaluate model performance with comparison to observations made during the Arctic Ocean 2018 expedition, where a suite of remote-sensing instrumentation was active aboard the Swedish icebreaker <em>Oden </em>measuring summertime Arctic cloud and boundary layer properties. We find that both models do not reproduce cloud fractions well at altitude (up to 8 km) and overestimate the occurrence of low (<1 km) clouds during the sea ice melt period of the expedition. Low cloud agreement with observations improves when the sea ice begins to refreeze; however, the underestimation of cloud aloft remains consistent regardless of sea ice conditions. In this presentation, we will indicate which model processes need to be improved to capture these summertime Arctic clouds more effectively.</p>

Physical and Chemical Properties of Cloud Droplet Residuals and Aerosol Particles During the Arctic Ocean 2018 Expedition

“…For points above the boundary layer no further distinction was made between land, ocean, or ice. The Arctic boundary layer is difficult to accurately represent in models (Birch et al., 2012; Graham et al., 2019; Sotiropoulou et al., 2016; Tjernström et al., 2021; Young et al., 2021). However, varying the ECMWF boundary layer pressure by ±15 hPa or assuming a constant value (965 hPa, which corresponds to the mean boundary layer pressure along all trajectory data points started from the lowest model layer) did not significantly change the results or the patterns observed (see Figure S2 in Supporting Information ).…”