Coupling Between Land Surface Fluxes and Lifting Condensation Level: Mechanisms and Sensitivity to Model Physics Parameterizations

Biases in land-atmosphere interaction simulations may originate from different model components or parameterizations and are transferred to the land-atmosphere system, which causes biases in weather and climate predictions. With a focus on East Asia, we analyze the relationships between land surface sensible and latent heat fluxes (SH and LH), evaporative fraction (EF), soil moisture, and lifting condensation level (LCL) height in ERA5 and MERRA-2 reanalyzes and simulations from a regional climate model (CWRF) with multiple parameterizations. The results show that SH (soil moisture and EF) is generally positively (negatively) correlated with LCL height because of their mutual positive (negative) influence and the positive feedback loops. The LH-LCL relationship is sensitive to the local climate and generally positive in humid climates and negative in the semiarid climate; however, only negative correlations can be indicative of a possible impact of LH on LCL. MERRA-2 shows an overall stronger influence of land on LCL height than ERA5 and CWRF. Different CWRF parameterizations produce different and sometimes contrasting LH-LCL relationships, which is strongly related to the simulated climate and can be validated. This highlights the need for a deep process-level understanding of land-atmosphere interactions in coupled model simulations.

Automated summary

Biases in land-atmosphere interaction simulations can affect weather and climate predictions, with different components and parameterizations contributing to these biases. Analysis of data from East Asia shows varying relationships between land surface fluxes and lifting condensation level height, with different parameterizations in the regional climate model impacting these relationships. Further understanding of land-atmosphere interactions is crucial for improving coupled model simulations.