Measured and Modeled Historical Precipitation Trends for Svalbard

• Published in: Journal of hydrometeorology 2020-06, Vol.21 (6), p.1279-1296
• Main Authors: Førland, Eirik J., Isaksen, Ketil, Lutz, Julia, Hanssen-Bauer, Inger, Schuler, Thomas Vikhamar, Dobler, Andreas, Gjelten, Herdis M., Vikhamar-Schuler, Dagrun
• Format: Article
• Language: English
• ISSN: 1525-755X; 1525-7541
• DOI: 10.1175/JHM-D-19-0252.1

Precipitation plays an important role in the Arctic hydrological cycle, affecting different areas like the surface energy budget and the mass balance of glaciers. Thus, accurate measurements of precipitation are crucial for physical process studies, but gauge measurements in the Arctic are sparse and subject to relocations and several gauge issues. From Svalbard, we analyze precipitation trends at six weather stations for the last 50–100 years by combining different observation series and adjusting for inhomogeneities. For the past 50 years, the measured annual precipitation has increased by 30%–45%. However, precipitation measurements in the cold and windy climate are strongly influenced by gauge undercatch. Correcting for undercatch reduces the trend values by 10% points, since the fraction of solid precipitation has decreased and undercatch is larger for solid precipitation. Thus, precipitation corrected for undercatch should be used to study “true” precipitation trends in the Arctic. Precipitation over Svalbard has been modeled by downscaling reanalysis data to a spatial resolution of 1 km. In general, the modeled annual precipitation is higher (13%–175%) than the measured values and mainly higher than the precipitation corrected for undercatch. Although the model resolves orographic effects on a regional scale, the downscaling is not able to reproduce local orographic enhancement for onshore winds, nor local effects of rain shadow. The downscaled dataset explains approximately 60% of the interannual precipitation variability. The model-based trends during 1979–2018 are positive, but weaker (∼4% decade−1) than the observed (∼8% decade−1) trends.