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

a result, the SLP minimum is reached just two hours later than in the other simulations. With a shorter lifetime than the other simulated PLs, the PL in 23d12h deepens slightly less than the others and, therefore, its associated SLP minimum is closer to the observed one. Compared to the simulations, the PL in ERA5 deepens less, corresponding better to the observations. The evolution of the SLP at the centre of the PL in ERA5 follows closely the observations, and the SLP in ERA5 attains a minimum of 998.6 hPa at 1600 UTC. 3.3 Verification of the simulated PL against observations affected by the PL 3.3.1 Sea level pressure. As expected, all simulations except for 24d12h and 24d18h notably overestimate SLP, particularly the lowest observed SLP values (Fig 7). In contrast, 24d12h and 24d18h underestimate many SLP values between 1000 and 1010 hPa. The aggregate statistics show that 24d12h and 24d18h have lower absolute mean bias, higher accuracy and higher correla- tion coefficient than the other simulations (Table 2). Whereas both 24d12h and 24d18h have a ME of -0.2 hPa, the ME of the other simulations ranges from 2.1 to 3.5 hPa. The RMSE of 24d12h and 24d18h (2 hPa and 1.4 hPa, respectively) is considerably lower than that of the other simula- tions (between 3.2 hPa and 4.5 hPa). The Spearman correlation coefficient of 24d12h and 24d18h shows that they have, respectively, a strong and a very strong positive correlation with the obser- vations. Except for 23d12h and 23d18h, which show a quite strong correlation with the observa-

tions, the other simulations show either weak or modest correlation. Fig 6. Time series of (a) the distance between the centre of the observed PL and the centre of the PL in the simulations and ERA5, and (b) the SLP at the centre of the PL in the simulations and ERA5, and the SLP observed at the surface station the closest to the centre of the observed PL. https://doi.org/10.1371/journal.pone.0292250.g006 PLOS ONE Assessment of simulations of a polar low with the canadian regional climate model PLOS ONE | https://doi.org/10.1371/journal.pone.0292250 October 5, 2023 11 / 28