Understanding the behavior of tropical diurnal convection in the E3SM Atmosphere Model using TWP-ICE Cases
Authors
Wuyin Lin — Brookhaven National Laboratory
Shaocheng Xie — Lawrence Livermore National Laboratory
Guang Zhang — University of California, San Diego
Robert Jackson — Argonne National Laboratory
Satoshi Endo — Brookhaven National Laboratory
Andrew M. Vogelmann — Brookhaven National Laboratory
Scott Matthew Collis — Argonne National Laboratory
Jean-Christophe Golaz — Lawrence Livermore National Laboratory
Category
Convective clouds, including aerosol interactions
Description
This work aims to investigate the behavior of tropical diurnal convection in the U.S. DOE’s Energy Exascale Earth System Model (E3SM) through the lens of the model evolution. In particular, the evolution involves new physical parameterization and an increase in model resolution, both of which directly impact how convection in the model comes into effect. It is found that the use of Cloud Layers Unified By Binormals (CLUBB) has the effect equivalent to buffering the convective instability to delay peak convective precipitation, hence mitigating the diurnal biases commonly seen in climate models that tend to be phase-locked to the diurnal variation of surface fluxes over land due to convective triggering mechanism. Increase in vertical resolution modifies the implied convective cloud spectrum in the bulk convective scheme, requiring changes to multiple key elements to adapt the scheme to the new model configuration. Change in launching level is found to have large impact on simulated diurnal precipitation, with a launching level closer to surface tending to have later peak convective precipitation relative to local noon – contrary to the expected response that a lower launching level would lead to convective triggering more in sync with the variation of near surface fluxes. The diurnal precipitation characteristics in the E3SM over the maritime continents during the TWP-ICE campaign period are found consistent with that from long-term climate simulation. TWP-ICE cases are therefore used to help understand the model diurnal behavior. The results are also expected to be beneficial to the tuning of the E3SM Atmosphere Model.
