TY - JOUR N2 - Unique and independent historical observations, carried out in the central Arctic during the early twentieth century warming (ETCW) period, were used to evaluate the older (20CRv2) and newer (20CRv2c) versions of the 20th Century Reanalysis and the HIRHAM5 regional climate model. The latter can reduce several biases compared to its forcing data set (20CRv2) probably due to higher horizontal resolution and a more realistic cloud parameterization. However, low-level temperature and near-surface specific humidity agree best between 20CRv2c and the surface-based observations. This better performance results from more realistic lower boundary conditions for sea ice concentration and sea surface temperature, but it is limited mainly to polar night. Although sea level pressures are very similar, the vertical stratification and baroclinicity change in the transition from 20CRv2 to 20CRv2c. Compared to observed temperature profiles, the systematic cold bias above 400 hPa remains almost unchanged indicating an incorrect coupling between the planetary boundary layer and free troposphere. In addition to surface pressures, it is therefore recommended to assimilate available vertical profiles of temperature, humidity and wind speed. This might also reduce the large biases in 10 m wind speed, but the reliability of the sea ice data remains a great unknown. L1 - http://www.journals.pan.pl/Content/103313/PDF/Polish%20Polar%202-18%203-D.Klaus%20i%20in..pdf L2 - http://www.journals.pan.pl/Content/103313 PY - 2018 IS - No 2 EP - 254 KW - Arctic KW - 20th Century Reanalysis KW - regional climate model KW - early twentieth century warming A1 - Klaus, Daniel A1 - Wyszyński, Przemysław A1 - Dethloff, Klaus A1 - Przybylak, Rajmund A1 - Rinke, Annette PB - Polish Academy of Sciences PB - Committee on Polar Research VL - vol. 39 DA - 2018.06.15 T1 - Evaluation of 20CR reanalysis data and model results based on historical (1930–1940) observations from Franz Josef Land SP - 225 UR - http://www.journals.pan.pl/dlibra/publication/edition/103313 T2 - Polish Polar Research ER -