The Summertime Precipitation Bias in E3SM Atmosphere Model Version 1 over the Central United States. Issue 16 (17th August 2019)

• Record Type: Journal Article
• Authors: Zheng, X.; Golaz, J.‐C.; Xie, S.; Tang, Q.; Lin, W.; Zhang, M.; Ma, H.‐Y.; Roesler, E. L.
• Is Part Of: Journal of geophysical research. Volume 124:Issue 16(2019)
• Page Start: 8935
• Page End: 8952
• Publication Date: 2019-08-17
• Subjects: GCM -- E3SM -- precipitation -- convection parameterization; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2019JD030662
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: This study analyzes the summertime precipitation bias over the Central United States and its relationship to the simulated large‐scale environment and the convection scheme in the Energy Exascale Earth System Model Atmosphere Model version 1. This relationship is mainly examined in a set of short‐term hindcasts initialized with realistic large‐scale conditions for the summer of 2011. Besides the uniform 1° model resolution, we adopt Regionally Refined Meshes to increase the model resolution to 0.25° over the contiguous United States. Additional five‐year Atmospheric Model Intercomparison Project simulations are conducted to confirm that the results from the hindcasts are consistent with the climate runs. We find that the summertime dry precipitation bias over the Great Plains and the wet bias over the Rockies cannot be reduced simultaneously by changing resolution or tuning parameters. As for the diurnal cycle, Energy Exascale Earth System Model Atmosphere Model version 1 captures the general diurnal variation of the large‐scale moisture transport and the large‐scale upward motion over the Central United States. However, the diurnal cycle of precipitation over the Great Plains is out of phase with the diurnal variation of the large‐scale environment because the convective precipitation dominates the total precipitation and its diurnal cycle, and it does not directly respond to the local moisture convergence and the large‐scale upward motion. These results reemphasize the importance of improving the coupling of the convection to the large‐scale environment in reducing the summer precipitation bias over the Central United States in climate models with the resolution of ~0.25°. Key Points: EAMv1 captures the diurnal cycle of the large‐scale environment but misrepresents the diurnal cycle of precipitation over the Central United States Hindcast simulations provide insights on the relationship between the precipitation bias and the large‐scale environment over the Central United States The coupling of the convection to the large‐scale environment needs to be improved