On the possibilities to use atmospheric reanalyses to evaluate the warming structure in the Arctic
- ISSN: 16807316
- DOI: 10.5194/acp-13-11209-2013
There has been growing interest in the vertical structure of the recent\nArctic warming. We investigated temperatures at the surface, 925, 700,\n500 and 300 hPa levels in the Arctic (north of 70 degrees N) using\nobservations and four reanalyses: ERA-Interim, CFSR, MERRA and NCEP II.\nFor the period 1979-2011, the layers at 500 hPa and below show a warming\ntrend in all seasons in all the chosen reanalyses and observations.\nRestricting the analysis to the 1998-2011 period, however, all the\nreanalyses show a cooling trend in the Arctic-mean 500 hPa temperature\nin autumn, and this also applies to both observations and the reanalyses\nwhen restricting the analysis to the locations with available IGRA\nradiosoundings. During this period, the surface observations mainly\nrepresenting land areas surrounding the Arctic Ocean reveal no\nsummertime trend, in contrast with the reanalyses whether restricted to\nthe locations of the available surface observations or not.\nIn evaluating the reanalyses with observations, we find that the\nreanalyses agree better with each other at the available IGRA sounding\nlocations than for the Arctic average, perhaps because the sounding\nobservations were assimilated into reanalyses. Conversely, using the\nreanalysis data only from locations matching available surface (air)\ntemperature observations does not improve the agreement between the\nreanalyses. At 925 hPa, CFSR deviates from the other three reanalyses,\nespecially in summer after 2000, and it also deviates more from the IGRA\nradiosoundings than the other reanalyses do. The CFSR error in summer\nT-925 is due mainly to underestimations in the Canadian-Atlantic sector\nbetween 120 degrees W and 0 degrees. The other reanalyses also have\nnegative biases in this longitude band.