The accuracy of climate variability and trends across Arctic Fennoscandia in four reanalyses

Observations reveal a statistically significant warming across Arctic Fennoscandia: three reanalyses show a similar regional warming of smaller magnitude while the fourth is anomalous, even having a slight cooling in some areas. Spatial patterns of precipitation trends across the region differ markedly between the reanalyses, which have varying success at matching observations but generally fail to replicate sites with significant observed trends. There is a clear spatial mismatch between reanalyses and observations in regions of steep and complex orography. Arctic Fennoscandia has undergone significant climate change over recent decades. Reanalysis data sets allow us to understand the atmospheric processes driving such changes. Here we evaluate four reanalyses against observations of near‐surface air temperature (SAT) and precipitation (PPN) from 35 meteorological stations across the region for the 35‐year period from 1979 to 2013. The reanalyses compared are the National Centers for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR), the European Centre for Medium‐Range Weather Forecast (ECMWF) Interim reanalysis (ERA‐Interim), the Japanese Meteorological Agency (JMA) 55‐year reanalysis (JRA‐55) and National Aeronautics and Space Administration (NASA)’s Modern‐Era Retrospective Analysis for Research and Applications (MERRA). All four reanalyses have an overall small cool bias across Arctic Fennoscandia, with MERRA typically ~1 °C cooler than the others. They generally reproduce the broad spatial patterns of mean SAT across the region, although less well in areas of complex orography. Observations reveal a statistically significant warming across Arctic Fennoscandia, with the majority of trends significant at p