The accuracy of climate variability and trends across Arctic Fennoscandia in four reanalyses
International Journal of Climatology
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Marshall, G., Kivinen, S., Jylhä, K., Vignols, R., & Rees, G. (2018). The accuracy of climate variability and trends across Arctic Fennoscandia in four reanalyses. International Journal of Climatology https://doi.org/10.1002/joc.5541
Arctic Fennoscandia has undergone significant climate change over recent decades. Reanalysis datasets 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 1979-2013. 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 < 0.01. Three reanalyses show similar regional warming but of smaller magnitude while CFSR is anomalous, even having a slight cooling in some areas. In general the other reanalyses are sufficiently accurate to correctly reproduce the varying significance of observed seasonal trends. There are much greater differences between the reanalyses when comparing PPN to observations. MERRA-Land, which merges a gauge-based dataset, is clearly the best: CFSR is the least successful, with a significant wet bias. The smoothed reanalysis orography means that the high PPN associated with the western side of the Scandinavian Mountains extends too far inland. Spatial patterns of PPN trends across the region differ markedly between the reanalyses, which have varying success at matching observations and generally fail to replicate sites with significant observed trends. Therefore, using reanalyses to analyse PPN changes in Arctic Fennoscandia should be undertaken with caution.
G.J.M. was supported by the UK Natural Environment Research Council (NERC) through the British Antarctic Survey research programme Polar Science for Planet Earth. K.J. was partially funded by the Academy of Finland (Decision No. 278067 for the PLUMES project). R.M.V. is funded by NERC PhD studentship NE/L002507/1.
External DOI: https://doi.org/10.1002/joc.5541
This record's URL: https://www.repository.cam.ac.uk/handle/1810/275894
Attribution 4.0 International
Licence URL: http://creativecommons.org/licenses/by/4.0/
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