Lee Junhong, Hohenegger Cathy
Max Planck Institute for Meteorology, Hamburg 20146, Germany.
Proc Natl Acad Sci U S A. 2024 Mar 19;121(12):e2314265121. doi: 10.1073/pnas.2314265121. Epub 2024 Mar 12.
The debate on the sign of the soil moisture-precipitation feedback remains open. On the one hand, studies using global coarse-resolution climate models have found strong positive feedback. However, such models cannot represent convection explicitly. On the other hand, studies using km-scale regional climate models and explicit convection have reported negative feedback. Yet, the large-scale circulation is prescribed in such models. This study revisits the soil moisture-precipitation feedback using global, coupled simulations conducted for 1 y with explicit convection and compares the results to coarse-resolution simulations with parameterized convection. We find significant differences in a majority of points with feedback that is weaker and dominantly negative with explicit convection. The model with explicit convection is more often in a wet regime and prefers the triggering of convection over dry soil in the presence of soil moisture heterogeneity, in contrast to the coarse-resolution model. Further analysis indicates that the feedback not only between soil moisture and evapotranspiration but also between evapotranspiration and precipitation is weaker, in better agreement with observations. Our findings suggest that coarse-resolution models may not be well suited to study aspects of climate change over land such as changes in droughts and heatwaves.
关于土壤湿度 - 降水反馈的正负性争论仍未定论。一方面，使用全球粗分辨率气候模型的研究发现了强烈的正反馈。然而，这类模型无法明确表示对流。另一方面，使用千米尺度区域气候模型和显式对流的研究报告了负反馈。不过，此类模型中规定了大尺度环流。本研究使用具有显式对流的全球耦合模拟对土壤湿度 - 降水反馈进行了重新审视，模拟时长为1年，并将结果与具有参数化对流的粗分辨率模拟结果进行了比较。我们发现在大多数点上存在显著差异，显式对流时反馈较弱且主要为负。与粗分辨率模型相比，具有显式对流的模型更常处于湿润状态，并且在存在土壤湿度异质性的情况下，更倾向于在干燥土壤上触发对流。进一步分析表明，不仅土壤湿度与蒸散之间的反馈，而且蒸散与降水之间的反馈都较弱，这与观测结果更相符。我们的研究结果表明，粗分辨率模型可能不太适合研究诸如干旱和热浪变化等陆地气候变化方面。
