Lin et al. (2025) Enduring local impact of springtime snow cover over the Third Pole

Identification

• Journal: npj Climate and Atmospheric Science
• Year: 2025
• Date: 2025-12-11
• Authors: Changgui Lin, Kun Yang, Deliang Chen, Siyu Yue, Xu Zhou, Yonghui Lei, Jinmei Pan, Xi Cao, Yongkang Xue, Jiancheng Shi
• DOI: 10.1038/s41612-025-01264-w

Research Groups

• Key Laboratory of Microwave Remote Sensing Technology, National Space Science Center, Chinese Academy of Sciences, Beijing, China
• Department of Earth System Science, Tsinghua University, Beijing, China
• National Climate Centre, China Meteorological Administration, Beijing, China
• State Key Laboratory of Tibetan Plateau Earth System, Environment and Resources, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China
• State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences, Beijing, China
• Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
• Department of Geography, University of California, Los Angeles, Los Angeles, CA, USA

Short Summary

This study confirms the enduring local impact of springtime Third Pole snow cover (TPSC) on summer precipitation and proposes a self-sustaining mechanism where initial excessive precipitation releases atmospheric latent heat, driving anomalous circulation that favors subsequent precipitation.

Objective

• To verify the enduring local impact of springtime Third Pole snow cover (TPSC) on summer precipitation.
• To elucidate the underlying self-sustaining mechanism that maintains the cross-season link between springtime TPSC anomalies and summer precipitation.

Study Configuration

• Spatial Scale: Third Pole (TP) region, with a model domain of 500 × 300 grids at 0.09° spacing, centered at 36°N and 85°E.
• Temporal Scale: Numerical simulations from 1 January to 31 August 2018 (with spin-up before 1 March). Observational data span August 2002 to July 2022 for snow and 1979 to present for precipitation, with analysis focused on March to August.

Methodology and Data

• Models used:
  • Advanced Weather Research and Forecasting Model (WRF-ARW, version 4.0) with Noah-MP land surface model.
  • Linear Baroclinic Model (LBM) for examining atmospheric circulation response.
• Data sources:
  • Observational snow data: State-of-the-art dataset of multiple snow parameters for the Tibetan Plateau (3 km spatial resolution), derived from a physics-based snowpack model (SNTHERM) coupled with a microwave emission model and constrained by MODIS fractional snow cover.
  • Observational precipitation data: TPHiPr dataset for the TP region (1/30° spatial resolution), merging ERA5_CNN with gauge observations.
  • Reanalysis data: ERA5 from ECMWF for WRF initial and lateral boundary conditions, and for monthly atmospheric variables (vertically integrated moisture divergence, geopotential, air temperature, specific humidity, horizontal velocity, and vertical p-velocity) in the observational investigation.

Main Results

• A springtime TPSC deficit leads to excessive precipitation over the TP from March to August in simulations, with peak intensity in April and May.
• This precipitation anomaly is driven by enhanced moisture convergence and upward motion, associated with an enhanced high in the upper troposphere and a deepened low in the lower troposphere.
• Observational analysis generally corroborates these findings, showing more summer precipitation in "snow-deficient" years, particularly in the western TP, consistent with simulated moisture convergence and upper-tropospheric geopotential anomalies.
• The initial forcing from TPSC deficit involves increased surface sensible heat flux (up to 25 W m⁻²) and latent heat flux (up to 17 W m⁻²) in spring, but these surface heat sources diminish by summer.
• The enduring local impact is sustained by atmospheric heat sources, specifically the apparent moisture sink (Q2), which represents the release of atmospheric latent heat from net condensation. Q2 exhibits a persistent positive heating rate anomaly in the middle troposphere from spring to summer, highly correlated with precipitation.
• A self-sustaining mechanism is proposed: initial excessive precipitation, responding to enhanced surface heat and water fluxes from TPSC deficit, releases additional atmospheric latent heat, which in turn drives an anomalous circulation favoring subsequent precipitation.
• The springtime TPSC deficit also results in a negative apparent heat source (Q1) anomaly, primarily due to radiative cooling from increased cloud amount, contributing to an overall decline in air temperature difference.

Contributions

• Provides the first explicit verification and mechanistic explanation of the enduring local impact of springtime TPSC on summer precipitation over the Third Pole, a less-explored aspect compared to remote influences.
• Proposes a novel "self-sustaining mechanism" involving atmospheric latent heat release from precipitation anomalies, which maintains the cross-season link from spring TPSC to summer precipitation.
• Strengthens the understanding of cross-season influences of springtime TPSC on remote monsoons (e.g., Indian Summer Monsoon, East Asian Summer Monsoon) by establishing the local memory effect.
• Suggests that the Third Pole may experience increased summer precipitation in a warmer future due to projected decreases in springtime snow cover.
• Utilizes advanced, high-quality snow and precipitation datasets for the Tibetan Plateau, addressing data limitations of previous studies.

Funding

• Chinese Academy of Sciences-Pioneering Initiative Talents Program (Grant Number: E3RC2DQ31S)
• Key Laboratory of South China Sea Meteorological Disaster Prevention and Mitigation of Hainan Province (Grant Number: SCSF202401)
• Open Grants of the State Key Laboratory of Severe Weather (Grant Number: 2024LASW-B02)
• Contribution to LS4P-II | GEWEX
• Contribution to CORDEX-FPS-CPTP

Citation

@article{Lin2025Enduring,
  author = {Lin, Changgui and Yang, Kun and Chen, Deliang and Yue, Siyu and Zhou, Xu and Lei, Yonghui and Pan, Jinmei and Cao, Xi and Xue, Yongkang and Shi, Jiancheng},
  title = {Enduring local impact of springtime snow cover over the Third Pole},
  journal = {npj Climate and Atmospheric Science},
  year = {2025},
  doi = {10.1038/s41612-025-01264-w},
  url = {https://doi.org/10.1038/s41612-025-01264-w}
}