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<p>High-resolution regional climate simulations over the Tibetan Plateau (TP) remain challenging because of complex terrain, strong land-atmosphere interactions, and persistent wet and cold biases in climate models. In this study, the latest generation regional climate model RegCM5 is driven by ERA5 reanalysis. Seven gray-zone scale dynamical downscaling experiments are performed at 9&#xa0;km resolution over the TP for 2018–2021. The experiments are designed to evaluate the sensitivity of simulated precipitation and near-surface air temperature (T2m) to cumulus parameterization schemes (CPSs), microphysics parameterization schemes (MPSs), radiation transfer schemes (RTSs), and land surface models (LSMs). Model results are evaluated against observations from 132 meteorological stations and the Integrated Multi-satellite Retrievals for GPM (IMERG) version 6 satellite precipitation product. RegCM5 captures the broad southeast to northwest gradients and seasonal evolution of both precipitation and T2m. However, wet biases remain over the southern and southeastern TP during the warm season, while cold biases are most evident in winter. Summer precipitation remains the most difficult to reproduce. Its simulation is more sensitive to CPSs than to MPSs. The Kain–Fritsch scheme (CU2) reduces annual and summer precipitation errors, while the Grell scheme (CU4) produces the largest wet biases and larger deviations in heavy precipitation. Process diagnostics indicate that CPS-related precipitation differences are closely linked to precipitation partitioning, moisture transport, and vertical motion. In contrast, T2m is more directly affected by the choices of RTSs and LSMs through surface longwave and shortwave radiation, snow-albedo feedbacks, and land-atmosphere coupling. Overall, the CTL and CU2 experiments show relatively balanced performance and provide practical candidate configurations for future long-term gray-zone simulations over the TP. However, notable wet and cold biases remain across the experiments. These results provide a physically based reference for selecting and refining RegCM5 parameterization combinations in future TP climate simulations.</p>

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Sensitivity of physical parameterization in gray-zone regional climate simulation over the Tibetan Plateau using RegCM5

  • 期刊论文

  • 发表日期：

    2026年7月2日

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  • Yongxiang Guo,
  • Peifeng Zhou,
  • Mengnan Ma,
  • Yuncan Xiao,
  • Jianping Tang

摘要

High-resolution regional climate simulations over the Tibetan Plateau (TP) remain challenging because of complex terrain, strong land-atmosphere interactions, and persistent wet and cold biases in climate models. In this study, the latest generation regional climate model RegCM5 is driven by ERA5 reanalysis. Seven gray-zone scale dynamical downscaling experiments are performed at 9 km resolution over the TP for 2018–2021. The experiments are designed to evaluate the sensitivity of simulated precipitation and near-surface air temperature (T2m) to cumulus parameterization schemes (CPSs), microphysics parameterization schemes (MPSs), radiation transfer schemes (RTSs), and land surface models (LSMs). Model results are evaluated against observations from 132 meteorological stations and the Integrated Multi-satellite Retrievals for GPM (IMERG) version 6 satellite precipitation product. RegCM5 captures the broad southeast to northwest gradients and seasonal evolution of both precipitation and T2m. However, wet biases remain over the southern and southeastern TP during the warm season, while cold biases are most evident in winter. Summer precipitation remains the most difficult to reproduce. Its simulation is more sensitive to CPSs than to MPSs. The Kain–Fritsch scheme (CU2) reduces annual and summer precipitation errors, while the Grell scheme (CU4) produces the largest wet biases and larger deviations in heavy precipitation. Process diagnostics indicate that CPS-related precipitation differences are closely linked to precipitation partitioning, moisture transport, and vertical motion. In contrast, T2m is more directly affected by the choices of RTSs and LSMs through surface longwave and shortwave radiation, snow-albedo feedbacks, and land-atmosphere coupling. Overall, the CTL and CU2 experiments show relatively balanced performance and provide practical candidate configurations for future long-term gray-zone simulations over the TP. However, notable wet and cold biases remain across the experiments. These results provide a physically based reference for selecting and refining RegCM5 parameterization combinations in future TP climate simulations.