资源环境科技发展态势分析平台

A process-oriented diagnostic (POD) is introduced to measure the thermodynamic sensitivity of convection in climate models. The physical basis for this POD is the observed tropical precipitation-buoyancy relationship. Fast timescale precipitation and thermodynamic profiles over oceans are POD inputs; these are used to evaluate model precipitation sensitivities to lower-tropospheric measures of subsaturation (SUBSAT_L) and undilute conditional instability (CAPE_L). The POD is used to diagnose 24 CMIP6 models. Half the diagnosed models exhibit SUBSAT_L sensitivity close to observed, while 6 models are excessively sensitive. Parameter perturbation experiments with the Community Atmospheric Model (CAM5) support the physical basis for the POD. Increasing entrainment increases the CAM5 precipitation SUBSAT_L sensitivity. Switching off the convective scheme or modifying the convective trigger to be oversensitive to moisture reproduces the excessive SUBSAT_L sensitivity seen among CMIP6 models. Models with excessive SUBSAT_L sensitivities have precipitating mean states closer to grid-scale saturation and likely support more grid-scale convection.