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<p>This study investigates the influence of spectral nudging (SN) on the accuracy of precipitation and marine cloud simulations over the China Sea during the summer monsoon using the Weather Research and Forecasting (WRF) model. Through sensitivity experiments with diverse nudging variables and configurations, we assess how SN strategies and underlying dynamics shape precipitation outcomes. Results demonstrate that SN mitigated circulation anomalies, enhancing the accuracy of downscaled wind vectors, sea surface pressure, and geopotential height, which collectively improved precipitation simulation. Optimal performance was achieved by nudging horizontal wind and moisture with a shorter timescale above the planetary boundary layer (PBL) and a ~ 2000&#xa0;km wavelength, striking a balance between large-scale fidelity and mesoscale flexibility. While nudging wind and potential temperature yielded representative precipitation, it underestimated cloud fraction and suppressed convection. Temperature nudging enhanced lower-tropospheric moisture advection, whereas moisture nudging promoted deeper convection above 850&#xa0;hPa. Conversely, combined temperature and moisture nudging amplified diabatic heating and overstimulated convection, causing precipitation overestimation. Notably, moisture nudging enabled reliable simulations at coarser resolutions without cumulus parameterization, providing a viable approach for computationally limited regions. This study reveals the critical thermodynamics and convection mechanisms governing precipitation dynamics and underscores the critical role of moisture nudging in refining process representation within regional climate models.</p>

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On spectral nudging and dynamics to improve representation of marine cloud and precipitation over the China sea in summer

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年8月2日

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  • Wenfeng Lai,
  • Jianping Gan

摘要

This study investigates the influence of spectral nudging (SN) on the accuracy of precipitation and marine cloud simulations over the China Sea during the summer monsoon using the Weather Research and Forecasting (WRF) model. Through sensitivity experiments with diverse nudging variables and configurations, we assess how SN strategies and underlying dynamics shape precipitation outcomes. Results demonstrate that SN mitigated circulation anomalies, enhancing the accuracy of downscaled wind vectors, sea surface pressure, and geopotential height, which collectively improved precipitation simulation. Optimal performance was achieved by nudging horizontal wind and moisture with a shorter timescale above the planetary boundary layer (PBL) and a ~ 2000 km wavelength, striking a balance between large-scale fidelity and mesoscale flexibility. While nudging wind and potential temperature yielded representative precipitation, it underestimated cloud fraction and suppressed convection. Temperature nudging enhanced lower-tropospheric moisture advection, whereas moisture nudging promoted deeper convection above 850 hPa. Conversely, combined temperature and moisture nudging amplified diabatic heating and overstimulated convection, causing precipitation overestimation. Notably, moisture nudging enabled reliable simulations at coarser resolutions without cumulus parameterization, providing a viable approach for computationally limited regions. This study reveals the critical thermodynamics and convection mechanisms governing precipitation dynamics and underscores the critical role of moisture nudging in refining process representation within regional climate models.