Mascaut et al. (2026) Ground-based atmospheric measurements at the Onsala Space Observatory (Sweden): data & trends (2009–2025)

Identification

• Journal: Earth system science data
• Year: 2026
• Date: 2026-03-26
• Authors: Faustine Mascaut, Roger Hammargren, Peter Forkman
• DOI: 10.5194/essd-18-2265-2026

Research Groups

• Onsala Space Observatory, Chalmers University of Technology, Onsala, Sweden

Short Summary

This study presents and analyzes a comprehensive, long-term (2009-2025) dataset of ground-based atmospheric measurements from the Onsala Space Observatory, Sweden, revealing a statistically significant warming trend of approximately 0.15 kelvin per year, most pronounced in winter, and a significant decrease in rain rate intensity.

Objective

• To present and analyze a comprehensive, high-resolution, long-term (August 2009 – April 2025) dataset of ground-based atmospheric measurements from the Onsala Space Observatory (OSO), Sweden, and to identify inter-annual trends and seasonal variations in key meteorological parameters.

Study Configuration

• Spatial Scale: Onsala Space Observatory (OSO), located 45 kilometers south of Gothenburg, western Sweden (approximately 57.4° N latitude). Measurements were taken at approximately 16.1 meters above sea level for most sensors and 12 meters above sea level for the pyranometer.
• Temporal Scale: Data collected from August 2009 to April 2025 (15 years and 8 months). Trend analysis performed for the period 2010–2024. Data resolution is 1 minute for most parameters and 15 minutes for cloud cover.

Methodology and Data

• Models used: None explicitly used for analysis or simulation in this data description paper.
• Data sources:
  • Ground-based observations from the Onsala Space Observatory (OSO).
  • Vaisala Weather transmitter WXT520: Measures air temperature, relative humidity, atmospheric pressure, precipitation (rain rate, 1-hour and 24-hour accumulations), wind speed, wind gust, and wind direction.
  • Sky Imager ASI-16 (Sky camera): Estimates cloud cover using the FindCloudsTrinity (FCT) software.
  • SMP6-V Smart Pyranometer (Kipp & Zonen): Measures global horizontal solar irradiance.
  • North Atlantic Oscillation (NAO) indices from NOAA's Climate Prediction Center.

Main Results

• Temperature: A statistically significant warming trend of +0.1461 kelvin per year (p=0.003) was observed from 2010 to 2024, leading to an approximate 2.2 kelvin increase in the annual average temperature over 15 years. Winter warming was the most pronounced, increasing by approximately 0.3 kelvin per year (203.3% above the annual trend).
• Precipitation: A statistically significant downward trend in mean rain rate of -1.39 x 10⁻⁸ meters per second per year (equivalent to -0.05 millimeters per hour per year, p=0.001) was detected from 2010 to 2024. No statistically significant trends were found for 1-hour or 24-hour rainfall accumulations, nor for the frequency of measurable or heavy precipitation days.
• Relative Humidity: No statistically significant long-term trend was identified (p=0.323), but pronounced annual and diurnal cycles were observed.
• Atmospheric Pressure: No statistically significant long-term trend was found (p=0.64). Clear semidiurnal cycles with an amplitude of approximately 80 pascals were consistent with theoretical expectations and latitudinal trends.
• Wind: No statistically significant long-term trends for annual mean wind speed or gust magnitude. Dominant wind directions are West-Southwest and East-Northeast. Strongest winds occur during autumn and winter, primarily from the West-Southwest (marine origin). Windstorm activity was correlated with North Atlantic Oscillation (NAO) phases.
• Solar Irradiance & Cloud Cover: Solar irradiance exhibited clear annual and diurnal cycles, with maximum values exceeding 1200 watts per square meter in summer and frequently falling below 200 watts per square meter in winter. An inverse relationship with cloud cover was evident, though significant irradiance could still occur under moderate to high cloud conditions, particularly in summer.
• NAO Link: Specific atmospheric anomalies, such as particularly cold winters (2009–2010 and 2010–2011) and a particularly warm winter (2019–2020), were linked to negative and positive phases of the North Atlantic Oscillation, respectively.

Contributions

• Provides a unique, comprehensive, and high-resolution long-term (over 15 years) ground-based atmospheric dataset for a coastal site in Northern Europe, which is relatively uncommon for such regions.
• Offers valuable insights into local weather patterns, seasonal variations, and inter-annual trends in a region strongly influenced by oceanic and continental air masses and the North Atlantic Oscillation.
• Serves as a critical resource for climate monitoring, regional environmental studies, local trend attribution, and the development and evaluation of geophysical and atmospheric models in Northern Europe.
• Highlights the local expression of broader climate dynamics, including Arctic amplification patterns and regional warming trends.
• Makes the dataset publicly available via PANGAEA, thereby enhancing the reproducibility and consistency of climate research.

Funding

• The Onsala Space Observatory is supported by the Swedish Research Council, the Swedish Land Survey (Lantmäteriet), and Chalmers University of Technology.
• The publication of this article was funded by the Swedish Research Council, Forte, Formas, and Vinnova.

Citation

@article{Mascaut2026Groundbased,
  author = {Mascaut, Faustine and Hammargren, Roger and Forkman, Peter},
  title = {Ground-based atmospheric measurements at the Onsala Space Observatory (Sweden): data & trends (2009–2025)},
  journal = {Earth system science data},
  year = {2026},
  doi = {10.5194/essd-18-2265-2026},
  url = {https://doi.org/10.5194/essd-18-2265-2026}
}