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    Item type:Publication, Access status: with files ,
    Declining number of northern hemisphere land-surface frozen days under global warming and thinner snowpacks
    (Springer, 2026)
    Hatami, Shadi
    ;
    Zaerpour, Masoud
    ;
    Ballarin, André S.
    ;
    Adamowski, Jan Franklin
    ;
    Papalexiou, Simon Michael
    Freeze–thaw processes shape ecosystems, hydrology, and infrastructure across northern high latitudes. Here we use satellite-based observations from 1979–2021 across 47 northern hemisphere ecoregions to examine changes in the number of frozen land-surface days per year. We find widespread declines, with 70% of ecoregions showing significant reductions, primarily linked to rising air temperatures and thinning snowpacks. Causal analysis demonstrates that air temperature and snow depth exert consistent controls on the number of frozen days. A trend-informed assessment based on historical observations suggests a potential average loss of more than 30 frozen days per year by the end of the century, with the steepest decreases in Alaska, northern Canada, northern Europe, and eastern Russia. Scenario-based analysis indicates that each 1 °C increase in air temperature reduces frozen days by ~6-days, while each 1 cm decrease in snow depth leads to a ~ 3-day reduction. These shifts carry major ecological and socio-economic implications.
    Publicationtype: Journal Article
      23  12
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    Item type:Publication, Access status: without files ,
    Impacts of agriculture and snow dynamics on catchment water balance in the U.S. and Great Britain
    (2024-12)
    Zaerpour, Masoud
    ;
    Hatami, Shadi
    ;
    Ballarin, André S.
    ;
    Knoben, Wouter J.M.
    ;
    Papalexiou, Simon Michael
    The Budyko water balance is a fundamental concept in hydrology that links aridity to how precipitation is divided between evapotranspiration and streamflow. While the model is powerful, its ability to explain temporal changes and the influence of human activities and climate change is limited. Here we introduce a causal discovery algorithm to explore deviations from the Budyko water balance, attributing them to human interventions such as agricultural activities and snow dynamics. Our analysis of 1342 catchments across the U.S. and Great Britain reveals distinct patterns: in the U.S., snow fraction and irrigation alter the Budyko water balance predominantly through changes in aridity-streamflow relationships, while in Great Britain, deviations are primarily driven by changes in precipitation-streamflow relationships, notable in catchments with high cropland percentage. By integrating causal analysis with the Budyko water balance, we enhance understanding of how human activities and climate dynamics affect water balance, offering insights for water management and sustainability in the Anthropocene.
    Publicationtype: Journal Article
      17
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    Item type:Publication, Access status: without files ,
    European hot and dry summers are projected to become more frequent and expand northwards
    (Springer, 2024-07-31)
    Felsche, Elizaveta
    ;
    Böhnisch, Andrea
    ;
    Poschlod, Benjamin
    ;
    Ludwig, Ralf
    Heatwaves and dry spells are major climate hazards with far-reaching implications for health, economy, agriculture, and ecosystems. The frequency of compound hot and dry summers in Europe has risen in recent years. Here we present an examination of past extreme summers and compare them to future climate conditions. We use reanalysis data (2001–2022) and model data at three global warming levels: +1.2 °C, +2 °C, and +3 °C for nine selected sub-regions. Key findings indicate a significant increase in the frequency of most extreme past occurrences under 2 °C and 3 °C warming scenarios. For specific summers, the occurrence probability rises by up to 5–6 times from 2 °C to 3 °C. Moreover, our analysis reveals a notable northward shift in the climatology of hot and dry summers under 3 °C warming. The hot and dry climate observed in Eastern Europe under current conditions is anticipated to extend into substantial parts of the Baltic coast, Finland, and Scandinavia.
    Publicationtype: Journal Article
      9
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    Item type:Publication, Access status: without files ,
    Spatial partitioning of terrestrial precipitation reveals varying dataset agreement across different environments
    (Springer, 2024-04-23)
    Markonis, Yannis
    ;
    Vargas Godoy, Mijael Rodrigo
    ;
    Pradhan, Rajani Kumar
    ;
    Pratap, Shailendra
    ;
    Thomson, Johanna Ruth
    The study of the water cycle at planetary scale is crucial for our understanding of large-scale climatic processes. However, very little is known about how terrestrial precipitation is distributed across different environments. In this study, we address this gap by employing a 17-dataset ensemble to provide, for the first time, precipitation estimates over a suite of land cover types, biomes, elevation zones, and precipitation intensity classes. We estimate annual terrestrial precipitation at approximately 114,000 ± 9400 km<sup>3</sup>, with about 70% falling over tropical, subtropical and temperate regions. Our results highlight substantial inconsistencies, mainly, over the arid and the mountainous areas. To quantify the overall discrepancies, we utilize the concept of dataset agreement and then explore the pairwise relationships among the datasets in terms of “genealogy”, concurrency, and distance. The resulting uncertainty-based partitioning demonstrates how precipitation is distributed over a wide range of environments and improves our understanding on how their conditions influence observational fidelity.
    Publicationtype: Journal Article
      8