Assessment of simulations of a polar low with the Canadian Regional Climate Model

• Published in: PloS one 2023-10, Vol.18 (10), p.e0292250-e0292250
• Main Authors: Moreno-Ibáñez, Marta, Laprise, René, Gachon, Philippe
• Format: Article
• Language: English
• Subjects: Arctic research; Atmospheric models; Baroclinic instability; Boundary conditions; Case studies; Climate; Climate models; Comparative analysis; Convection; Cyclones; Datasets; Dynamic meteorology; Earth Sciences; Evaluation; Finite element method; Gravity waves; Ice; Initial conditions; Low temperature; Mesoscale cyclones; Modelling; Observations; Ocean surface; Physical Sciences; Polar lows; Polar regions; Regional climate models; Regional climates; Regions; Research and Analysis Methods; Severe weather; Simulation; Simulation methods; Surface fluxes; Temperature gradients; Weather; Weather conditions; Weather forecasting; Wind
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0292250

Polar lows (PLs), which are intense maritime polar mesoscale cyclones, are associated with severe weather conditions. Due to their small size and rapid development, PL forecasting remains a challenge. Convection-permitting models are adequate to forecast PLs since, compared to coarser models, they provide a better representation of convection as well as surface and near-surface processes. A PL that formed over the Norwegian Sea on 25 March 2019 was simulated using the convection-permitting Canadian Regional Climate Model version 6 (CRCM6/GEM4, using a grid mesh of 2.5 km) driven by the reanalysis ERA5. The objectives of this study were to quantify the impact of the initial conditions on the simulation of the PL, and to assess the skill of the CRCM6/GEM4 at reproducing the PL. The results show that the skill of the CRCM6/GEM4 at reproducing the PL strongly depends on the initial conditions. Although in all simulations the synoptic environment is favourable for PL development, with a strong low-level temperature gradient and an upper-level through, only the low-level atmospheric fields of three of the simulations lead to PL development through baroclinic instability. The two simulations that best captured the PL represent a PL deeper than the observed one, and they show higher temperature mean bias compared to the other simulations, indicating that the ocean surface fluxes may be too strong. In general, ERA5 has more skill than the simulations at reproducing the observed PL, but the CRCM6/GEM4 simulation with initialisation time closer to the genesis time of the PL reproduces quite well small scale features as low-level baroclinic instability during the PL development phase.