Lin et al. (2026) Persistence of frozen-period soil moisture modulates late-spring surface thermal anomalies in the Tibetan Plateau

Identification

• Journal: Climate Dynamics
• Year: 2026
• Date: 2026-03-31
• Authors: Zouxing Lin, Zhiyan Zuo, Renhe Zhang, Yifeng Lin
• DOI: 10.1007/s00382-026-08142-y

Research Groups

• Shanghai Investigation, Design and Research Institute Co., Ltd., Shanghai, China
• Department of Atmospheric and Oceanic Sciences, Institute of Atmospheric Sciences, Fudan University, Shanghai, China

Short Summary

This study reveals that the persistence of frozen-period soil moisture (SM) in the Tibetan Plateau (TP) significantly modulates late-spring surface air temperature (SAT) anomalies. It demonstrates that January SM anomalies influence May SAT by altering evapotranspiration and the partitioning of surface sensible and latent heat fluxes, with a particularly strong impact on daily maximum SAT extremes.

Objective

• To investigate the role of frozen-period soil moisture (SM) in modulating subsequent late-spring surface air temperature (SAT) anomalies over the Tibetan Plateau (TP).
• To elucidate the physical mechanisms through which freeze-thaw related SM influences late-spring surface thermal variability, aiming to provide a robust physical basis for improving subseasonal to seasonal (S2S) climate prediction.

Study Configuration

• Spatial Scale: Tibetan Plateau (average elevation exceeding 4000 m), with a focus on the central-eastern TP (29–36°N, 85–102°E). Data resolutions range from 0.25° × 0.25° to 1.25° × 1.25°.
• Temporal Scale: 1980–2020 (41 years). Analysis uses monthly data, specifically focusing on January (representing the frozen period) and May (representing late-spring and the freeze-thaw transition).

Methodology and Data

• Models used: The study primarily utilizes reanalysis datasets, which are products of land-surface and atmospheric general circulation models. Specifically, CPC soil moisture data is derived from a land-surface model, and MERRA-2 is from the GEOS-5 atmospheric general circulation model. The authors did not run new model simulations for this study.
• Data sources:
  • China Meteorological Administration (CMA) CN05.1: Monthly maximum, mean, and minimum 2 m surface air temperature (SAT) (0.25° × 0.25° horizontal resolution).
  • United States Climate Prediction Center (CPC): Column-integrated soil moisture (0–160 cm depth) (0.5° grid).
  • Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2): Monthly root soil moisture, surface flux fields (sensible heat flux (SH), latent heat flux (LH), evapotranspiration (EVP)), and atmospheric fields (0.5° × 0.5° resolution).
  • JRA-55 reanalysis (Japanese Meteorological Agency): Monthly soil moisture (0–100 cm), surface flux fields (SH, LH, EVP), and atmospheric fields (1.25° × 1.25° resolution).
  • 40-year CMA global Land surface Reanalysis dataset (CRA40-Land): Monthly soil moisture (0–10 cm, 10–40 cm, 40–100 cm depths), surface flux fields (SH, LH, EVP) (1° × 1° resolution).
  • European Centre for Medium-Range Weather Forecasts (ECMWF) ERA5: Monthly mean soil moisture (0–7 cm, 7–28 cm, 28–100 cm depths), surface flux fields (SH, LH, EVP), and atmospheric fields (1° × 1° resolution).
  • ETOPO5: Digital database of land and sea-floor elevations (5-minute latitude/longitude grid).
  • Methods: Conventional statistical methods including correlation, regression, and composite analysis. Statistical significance assessed using Student’s t-test. Linear trends removed from all variables. Vertically integrated water vapor (WV) and water vapor flux (WVF) calculations.

Main Results

• January soil moisture (SM) exhibits a significant negative correlation with subsequent May surface air temperature (SAT) over the central-eastern Tibetan Plateau (TP), with maximum correlation coefficients exceeding -0.5.
• The primary physical mechanism involves the persistence of January SM anomalies until May, which modulates evapotranspiration (EVP) and, consequently, the partitioning ratio of surface sensible heat flux (SH) to latent heat flux (LH) within the surface energy budget.
• Specifically, anomalously wet (dry) January SM conditions lead to enhanced (reduced) May EVP, increasing (decreasing) LH while decreasing (increasing) SH, which further results in cold (warm) SAT anomalies.
• The net radiation flux (Rn) shows no statistically significant difference, indicating that SM anomalies primarily induce SH anomalies by modulating the Bowen ratio (SH/LH), rather than through radiation feedback.
• Analysis of extreme SAT responses reveals that SM variability exerts the weakest influence on daily minimum SAT (Tmin), a moderate influence on daily mean SAT (Tmean), and the strongest effect on daily maximum SAT (Tmax).
• Quantitatively, an SM anomaly of 160 mm can induce SAT fluctuations of approximately 2.4 °C for Tmin, 3.2 °C for Tmean, and 4.2 °C for Tmax.

Contributions

• Provides a robust physical basis for understanding the drivers of late-spring thermal anomalies over the Tibetan Plateau, emphasizing the critical role of frozen-period soil moisture.
• Highlights the cryosphere memory effect, demonstrating how January soil moisture anomalies persist and influence subsequent late-spring thermal conditions through land-atmosphere interactions.
• Elucidates the specific mechanistic pathway: frozen-period SM persistence modulates May evapotranspiration, altering the partitioning of sensible and latent heat fluxes, which then drives SAT anomalies.
• Quantifies the differential impact of soil moisture variability on daily extreme temperatures, showing a disproportionately stronger modulation of daily maximum SAT.
• Advances the theoretical foundation for improving subseasonal to seasonal (S2S) climate prediction capabilities over the TP, a region recognized as a significant source of climate predictability.

Funding

• National Natural Science Foundation of China (Grant No. 42505020)
• China Postdoctoral Science Foundation (Grant No. 2025M773150)
• Shanghai Post-doctoral Excellence Program (Grant No. 2024466)
• Postdoctoral Fund Project of Shanghai Investigation, Design and Research Institute Co., Ltd. (Grant No. 2024QT(831)-001)

Citation

@article{Lin2026Persistence,
  author = {Lin, Zouxing and Zuo, Zhiyan and Zhang, Renhe and Lin, Yifeng},
  title = {Persistence of frozen-period soil moisture modulates late-spring surface thermal anomalies in the Tibetan Plateau},
  journal = {Climate Dynamics},
  year = {2026},
  doi = {10.1007/s00382-026-08142-y},
  url = {https://doi.org/10.1007/s00382-026-08142-y}
}