Sun et al. (2026) Linking rain-on-snow events to river floods in the Tianshan Mountains

Identification

• Journal: Weather and Climate Extremes
• Year: 2026
• Date: 2026-10-23
• Authors: Fan Sun, Ross Woods, Xingming Hao, Yupeng Li, Gonghuan Fang, Qixiang Liang, Mengtao Ci, Jingjing Zhang, Zulipiya Kulaixi
• DOI: 10.1016/j.wace.2026.100968

Research Groups

• Xinjiang Key Laboratory of Water Cycle and Utilization in Arid Zone, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, China
• State Key Laboratory of Desert and Oasis Ecology, Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, China
• Akesu National Station of Observation and Research for Oasis Agro-ecosystem, Aksu, Xinjiang, China
• School of Civil, Aerospace, and Design Engineering, University of Bristol, Bristol, UK
• University of the Chinese Academy of Sciences, Beijing, China
• Munich Climate Center and Earth System Modelling Group, Department of Aerospace and Geodesy, TUM School of Engineering and Design, Technical University of Munich, Munich, Germany

Short Summary

This study provides the first basin-scale assessment of rain-on-snow (ROS) events and their link to river floods in the Tianshan Mountains, revealing that only about 44% of potential flood-inducing ROS events translate into actual floods, with significant basin-dependent conversion efficiency and delayed hydrological responses.

Objective

• To provide the first basin-scale assessment of potential flood-inducing rain-on-snow (ROS-PF) and actual river-flood-generating ROS (ROS-AF) events across the Tianshan Mountains.
• To investigate the spatiotemporal distribution, trends, and hydrological contributions of ROS-PF events.
• To quantify the conditions under which ROS-PF events evolve into ROS-AF events in an arid high-mountain environment.

Study Configuration

• Spatial Scale: Tianshan Mountains, covering 40 watersheds with basin areas ranging from 234.2 km² to 19,740.7 km². ERA5-Land data at 0.1° spatial resolution (approximately 9 km).
• Temporal Scale: 1951–2019 (69 years), using daily data.

Methodology and Data

• Models used:
  • Hydrologiska Byråns Vattenavdelning (HBV) model (for streamflow reconstruction)
  • Long Short-Term Memory (LSTM) models (for streamflow reconstruction)
• Data sources:
  • ERA5-Land reanalysis (daily precipitation, snowfall, snow water equivalent (SWE), temperature, snowmelt)
  • Tianshan Watershed Streamflow (TSWS) dataset (observation-based reconstructed daily streamflow for 40 watersheds)

Main Results

• ROS-PF events are concentrated in spring (April–June) and mid-elevations (2.0–3.5 km), occurring within a narrow temperature window of −0.24 ± 1.49 °C.
• The frequency of ROS-PF events significantly increased over 1951–2019 at a rate of 0.007 events per year (p < 0.05), primarily driven by rising heavy rainfall occurrence rather than snow availability.
• ROS-PF events contributed on average 14.7% of the 6-day snowmelt total and 8.3% of the 6-day available-water total across the Tianshan basins.
• Only approximately 44% of ROS-PF events evolve into ROS-AF events, demonstrating strong basin-dependent conversion efficiency (e.g., Pochengzi basin: 91% conversion; Talgar basin: 4.11% conversion).
• Most ROS-AF events occur with a temporal lag, with approximately 70% occurring within one to six days after the ROS-PF event, and about 30% on the same day.
• ROS-AF events also show a significant increasing trend of 0.19 events per year (p < 0.05) across the Tianshan Basin.

Contributions

• Provides the first basin-scale assessment of potential flood-inducing and actual flood-generating rain-on-snow (ROS) events in the arid, high-mountain Tianshan region.
• Links ROS forcing to reconstructed high-flow responses across 40 watersheds, shifting the focus from potential hazards to realized high-flow events.
• Quantifies the spatiotemporal distribution, trends, hydrological contributions, and conversion efficiency of ROS events into actual floods in an arid mountain environment.
• Highlights that ROS does not uniformly amplify flood risk but reorganizes flood-generation pathways, offering crucial insights for flood forecasting and water management.
• Utilizes a novel, long-term, observation-based daily streamflow dataset (TSWS) to address data scarcity in the Tianshan Mountains.

Funding

• Xinjiang Key Laboratory of Water Cycle and Utilization in Arid Zone (XJYS0907-2025-05)
• National Natural Science Foundation of China (42601077)
• Strategic Priority Research Program of the Chinese Academy of Sciences (XDB0720101)
• Natural Science Foundation of Xinjiang Uygur Autonomous Region (2025D01B165)
• Tianchi Talent Program of Xinjiang
• European Union's Horizon Europe program through the project LIQUIDICE (101184962)
• Program of China Scholarship Council (202404910281)

Citation

@article{Sun2026Linking,
  author = {Sun, Fan and Woods, Ross and Hao, Xingming and Li, Yupeng and Fang, Gonghuan and Liang, Qixiang and Ci, Mengtao and Zhang, Jingjing and Kulaixi, Zulipiya},
  title = {Linking rain-on-snow events to river floods in the Tianshan Mountains},
  journal = {Weather and Climate Extremes},
  year = {2026},
  doi = {10.1016/j.wace.2026.100968},
  url = {https://doi.org/10.1016/j.wace.2026.100968}
}