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Assessing the effects of land surface heterogeneity on planetary boundary layer characteristics in E3SM

Presentation Date
Wednesday, December 16, 2020 at 6:06pm



Spatial heterogeneity of land surface affects turbulent mixing processes in the planetary boundary layer (PBL), influencing clouds, precipitation, as well as the surface climate. Traditional coupling between land and atmosphere in Earth system models (ESMs) neglects the heterogeneity at subgrid scale, potentially producing biases in PBL characteristics over complex land surfaces. In this study, we assess the effects of the surface heterogeneity on PBL characteristics in the U.S. Department of Energy’s Energy Exascale Earth System Model (E3SM) version 1 (E3SMv1). The model is configured as a single column model (SCM) for the Atmospheric Radiation Measurement (ARM) Southern Great Plain (SGP) site. The heterogeneous surface properties derived from the HydroBlocks land surface model that explicitly resolves the field scale spatial heterogeneity is implemented to affect the subgrid surface variances in E3SM’s turbulence parameterization Cloud Layers Unified By Binormals (CLUBB).

Results are compared with an alternative E3SMv1 SCM simulation where subgrid surface properties are assumed to be homogeneous. We find that accounting for the subgrid surface heterogeneity enhances the turbulent mixing in the PBL, raises the PBL height, elevates clouds to higher altitudes, and changes the precipitation. Sensitivity tests are also conducted to determine the role of each of the prescribed moments in affecting the PBL characteristics. These results are aimed at raising awareness about the possible implementation of the novel HydroBlocks in the E3SM Land Model (ELM) and the coupling between ELM and the E3SM Atmosphere Model (EAM) in order to better represent the land surface properties and their impacts in next generation ESMs.

Funding Program Area(s)