loading page

The effect of coupling between CLUBB turbulence scheme and surface momentum flux on global wind simulations
  • +2
  • Emanuele Silvio Gentile,
  • Ming Zhao,
  • Vincent E Larson,
  • Colin M. Zarzycki,
  • Zhihong Tan
Emanuele Silvio Gentile
NOAA/GFDL Princeton University

Corresponding Author:[email protected]

Author Profile
Ming Zhao
Author Profile
Vincent E Larson
University of Wisconsin-Milwaukee
Author Profile
Colin M. Zarzycki
Pennsylvania State University
Author Profile
Zhihong Tan
Princeton University
Author Profile


The higher-order turbulence scheme, Cloud Layers Unified by Binormals (CLUBB), is known for effectively simulating the transition from cumulus to stratocumulus clouds within leading atmospheric climate models. This study investigates an underexplored aspect of CLUBB: its capacity to simulate near-surface winds and the Planetary Boundary Layer (PBL), with a particular focus on its coupling with surface momentum flux. Using the GFDL atmospheric climate model (AM4), we examine two distinct coupling strategies, distinguished by their handling of surface momentum flux during the CLUBB’s stability-driven substepping performed at each atmospheric time step. The static coupling maintains a constant surface momentum flux, while the dynamic coupling adjusts the surface momentum flux at each CLUBB substep based on the CLUBB-computed zonal and meridional wind speed tendencies. Our 30-year present-day climate simulations (1980-2010) show that static coupling overestimates 10-m wind speeds compared to both control AM4 simulations and reanalysis, particularly over the Southern Ocean (SO) and other midlatitude ocean regions. Conversely, dynamic coupling corrects the static coupling 10-m winds biases in the midlatitude regions, resulting in CLUBB simulations achieving there an excellent agreement with AM4 simulations. Furthermore, analysis of PBL vertical profiles over the SO reveals that dynamic coupling reduces downward momentum transport, consistent with the found wind-speed reductions. Instead, near the tropics, dynamic coupling results in minimal changes in near-surface wind speeds and associated turbulent momentum transport structure. Notably, the wind turning angle serves as a valuable qualitative metric for assessing the impact of changes in surface momentum flux representation on global circulation patterns.
08 Mar 2024Submitted to ESS Open Archive
10 Mar 2024Published in ESS Open Archive