Biget et al. (2025) Brief communication: Sharp precipitation gradient on the southern edge of the Tibetan Plateau during cold season

Identification

• Journal: ˜The œcryosphere
• Year: 2025
• Date: 2025-11-18
• Authors: Titouan Biget, Fanny Brun, Walter W. Immerzeel, Léo Martin, Hamish D. Pritchard, Emily Collier, Yanbin Lei, Tandong Yao
• DOI: 10.5194/tc-19-5863-2025

Research Groups

• Université Grenoble Alpes, CNRS, INRAE, IRD, Grenoble INP, IGE, France
• Department of Physical Geography, Utrecht University, the Netherlands
• Aix Marseille Univ, CNRS, IRD, INRAE, CEREGE, Aix-en-Provence, France
• British Antarctic Survey, United Kingdom
• Department of Atmospheric and Cryospheric Sciences (ACINN), University of Innsbruck, Austria
• Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, China
• CAS Center for Excellence in Tibetan Plateau Earth System Sciences, China

Short Summary

This study documents a sharp, order-of-magnitude precipitation gradient over a 10 km distance at the southern edge of the Tibetan Plateau during the cold season, using novel in-situ lake water pressure measurements, automatic weather station data, and atmospheric models. It reveals that precipitation totals can vary by a factor of ten over a short distance, marking the transition between the Great Himalayas and the Tibetan Plateau.

Objective

• To document and quantify the sharp precipitation gradient at the southern edge of the Paiku Co catchment (southern Tibetan Plateau) during the cold season (December to May) using novel lake water pressure measurements, conventional automatic weather station (AWS) data, and atmospheric model outputs.
• To evaluate the ability of reanalysis (ERA5-Land) and convection-permitting atmospheric models (CORDEX-FPS CPTP) to reproduce this complex precipitation distribution in a data-scarce, high-altitude region.

Study Configuration

• Spatial Scale: Southern Paiku Co basin (southern Tibetan Plateau, China) and northern Langtang National Park (Nepal). Specific sites include Golojang Co (proglacial lake at 5357 m a.s.l., 5.54 km²), Paiku AWS (5033 m a.s.l.), and Yala AWS (5090 m a.s.l.). The distance between Golojang Co and Paiku AWS is approximately 10 km.
• Temporal Scale: In-situ observations from November 2019 to May 2022, focusing on the cold season (December to May). Model simulations cover October 2019 to September 2020 (CPTP) and October 2019 to May 2022 (ERA5-Land for comparison), with a climatological analysis using ERA5-Land data from 1993 to 2022.

Methodology and Data

• Models used:
  • ERA5-Land reanalysis (approximately 10 km spatial resolution).
  • CORDEX-FPS CPTP (Convection-Permitting Third Pole) ensemble (2.2–4 km spatial resolution, reprojected to approximately 4 km).
• Data sources:
  • In-situ water pressure time series from three Hobo U20 pressure transducers installed in Golojang Co, interpreted as precipitation estimates using the method by Pritchard et al. (2021).
  • In-situ precipitation measurements from two Automatic Weather Stations (AWS): Paiku AWS (China) and Yala AWS (Nepal), equipped with OTT Pluvio2 gauges.
  • Lake ice cover extent mapped from Landsat 7, 8, and Sentinel-2 images using the Google Earth Engine Digitisation Tool (GEEDiT).
  • ERA5 integrated water vapor transport data for climatological analysis.

Main Results

• A sharp precipitation gradient exists at the southern edge of the Tibetan Plateau during the cold season (December to May), with precipitation totals varying by an order of magnitude over a short distance of approximately 10 km.
• Estimated cumulative snowfall at Golojang Co from lake pressure transducers was 420 ± 46 mm (Dec 2019–May 2020), 307 ± 27 mm (Dec 2020–May 2021), and 211 ± 9 mm (Dec 2021–Apr 2022).
• Paiku AWS, located approximately 10 km from Golojang Co and 350 m lower in elevation, recorded significantly less precipitation: 35 mm (9% of Golojang) in 2019-2020, 25 mm (8% of Golojang) in 2020-2021, and 12 mm (6% of Golojang) in 2021-2022.
• Yala AWS, located on the southern side of the Himalaya, recorded similar precipitation totals to Golojang Co (e.g., 289 mm, 94% of Golojang, in 2020-2021).
• Both ERA5-Land and CPTP models largely overestimated precipitation at Paiku AWS (ERA5-Land by 11 times, CPTP by 3.4 times).
• At Golojang Co, CPTP estimates for 2019-2020 were consistent with lake pressure records (1.2% difference), while ERA5-Land significantly underestimated precipitation (lake estimates were 1230% higher).
• CPTP, with its finer resolution, better resolved the spatial variability and sharp local gradients of precipitation compared to ERA5-Land, showing higher precipitation above 5000 m a.s.l. and on southern Himalayan slopes.
• Climatological analysis using ERA5-Land (1993-2022) suggests that precipitation gradients between Yala and the Paiku basin are stronger during the cold season compared to the monsoon season.

Contributions

• Provides the first documentation and quantification of an extreme, order-of-magnitude precipitation gradient on the southern edge of the Tibetan Plateau during the cold season, utilizing a unique combination of novel lake pressure measurements and conventional AWS data.
• Demonstrates the viability and value of using frozen lake water pressure time series as spatially averaged precipitation gauges in remote, data-scarce, high-altitude environments.
• Offers a critical evaluation of the performance of global reanalysis (ERA5-Land) and convection-permitting regional climate models (CORDEX-FPS CPTP) in representing complex orographic precipitation in the Himalayas, highlighting the superior ability of kilometer-scale models to resolve sharp gradients.
• Suggests a seasonal variation in precipitation distribution patterns, with sharper gradients observed during the cold season (winter and pre-monsoon) compared to the monsoon season, based on long-term reanalysis data.

Funding

• Ministère de l’Education Nationale, de l’Enseignement Supérieur et de la Recherche (agence nationale de la recherche and Chaire de professeur junior).

Citation

@article{Biget2025Brief,
  author = {Biget, Titouan and Brun, Fanny and Immerzeel, Walter W. and Martin, Léo and Pritchard, Hamish D. and Collier, Emily and Lei, Yanbin and Yao, Tandong},
  title = {Brief communication: Sharp precipitation gradient on the southern edge of the Tibetan Plateau during cold season},
  journal = {˜The œcryosphere},
  year = {2025},
  doi = {10.5194/tc-19-5863-2025},
  url = {https://doi.org/10.5194/tc-19-5863-2025}
}