Artificial Trends or Real Changes? Investigating Precipitation Records in Ny-Ålesund, Svalbard

Abstract

Abstract The Svalbard archipelago, in the Atlantic–Arctic region, has been affected by a strong increase in precipitation in the last decades, with major potential impacts for the cryosphere, biogeochemical cycles, and the ecosystems. Ny-Ålesund (79°N), in the northwest part of Svalbard, hosts invaluable meteorological records widely used by many researchers. Among the observed parameters, the amount of precipitation is subject to large biases, mainly due to the well-known precipitation gauges undercatch during windy conditions. The purpose of this study is to investigate if the observed trend of precipitation in Ny-Ålesund in the 1975–2022 period was real and how it was impacted by the gauge undercatch. We applied several correction factors developed in the last decades, based on local wind speed and temperature. We forced these corrections with 12-hourly precipitation data from the Ny-Ålesund weather station. Taking the period 1975–2022, the trend of precipitation increased from 3.8 mm yr−1 in the observations to 4.5 mm yr−1 (±0.2) after the corrections, mainly due to enhanced snowfall in November–January months. Taking the most recent 40-yr period (1983–2022), the amount of precipitation still increased by 3.8 mm yr−1 in the observations, but only by 2.6 mm yr−1 (±0.5) after the corrections. The recent observed trend of precipitation stays large due to an increase of wet snowfall and rainfall that are measured more efficiently by the precipitation gauge. This result shows the need of applying correction factors when using precipitation gauge data, especially in regions exhibiting large interannual changes of weather conditions. Significance Statement The purpose of this study is to investigate if the observed trend of precipitation in Ny-Ålesund in the 1975–2022 period was real and how it was impacted by the gauge undercatch. The results show that the observed trend of precipitation was overestimated when calculated in the most recent 40-yr period (1983–2022). This overestimation was large due to an increase with time of wet snowfall and rainfall that were measured more efficiently by the precipitation gauge. This result shows the need of applying corrections factors when using precipitation gauge data, especially in regions exhibiting large interannual changes of weather conditions.