Arctic warming, moisture increase and circulation changes observed in the Ny-Ålesund homogenized radiosonde record
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Radiosonde measurements obtained at the Arctic site Ny-Ålesund (78.9°N, 11.9°E), Svalbard, from 1993 to 2014 have been homogenized accounting for instrumentation discontinuities by correcting known errors in the manufacturer provided profiles. The resulting homogenized radiosonde record is provided as supplementary material at http://doi.pangaea.de/10.1594/PANGAEA.845373. From the homogenized data record, the first Ny-Ålesund upper-air climatology of wind, temperature and humidity is presented, forming the background for the analysis of changes during the 22-year period. Particularly during the winter season, a strong increase in atmospheric temperature and humidity is observed, with a significant warming of the free troposphere in January and February up to 3 K per decade. This winter warming is even more pronounced in the boundary layer below 1 km, presumably amplified by mesoscale processes including e.g. orographic effects or the boundary layer capping inversion. Though the largest contribution to the increasing atmospheric water vapour column in winter originates from the lowermost 2 km, no increase in the contribution by specific humidity inversions is detected. Instead, we find an increase in the humidity content of the large-scale background humidity profiles. At the same time, the tropospheric flow in winter is found to occur less frequent from northerly directions and to the same amount more frequent from the South. We conclude that changes in the atmospheric circulation lead to an enhanced advection of warm and moist air from lower latitudes to the Svalbard region in the winter season, causing the warming and moistening of the atmospheric column above Ny-Ålesund, and link the observations to changes in the Arctic Oscillation.
KeywordsPolar Vortex Arctic Oscillation Free Troposphere Radiosonde Data Arctic Oscillation Index
The authors would like to thank the overwintering staff of the AWIPEV research base (former Koldewey station) in Ny-Ålesund for the devoted launches of thousands of radiosondes contributing to this study. Special thanks to Jürgen Graeser, Siegrid Debatin and Holger Deckelmann for technical hard- and software support. We also thank the GRUAN Lead Centre for reprocessing early Ny-Ålesund RS92 radiosonde data. Furthermore, we thank Sabine Erxleben and Dörthe Handorf for calculating AO patterns and indices and for helpful discussions during the review process. We thank the reviewers for their helpful comments.
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