Preprints
https://doi.org/10.5194/gmd-2022-283
https://doi.org/10.5194/gmd-2022-283
Submitted as: model evaluation paper
 | 
08 Feb 2023
Submitted as: model evaluation paper |  | 08 Feb 2023
Status: this preprint is currently under review for the journal GMD.

Intercomparison of the weather and climate physics suites of a unified forecast/climate model system (GRIST-A22.7.28) based on single column modeling

Xiaohan Li, Yi Zhang, Xindong Peng, Baiquan Zhou, Jian Li, and Yiming Wang

Abstract. As a unified weather-forecast/climate model system, Global-to-Regional Integrated forecast SysTem (GRIST-A22.7.28) currently employs two separate physics suites for weather forecast and typical long-term climate simulation, respectively. Previous AMIP-style experiments have suggested that the weather (PhysW) and climate (PhysC) physics suites, when coupled to a common dynamical core, lead to different behaviors in terms of modeling clouds and precipitation. To explore the source of their discrepancies, this study compares the two suites using a single column model (SCM). The SCM simulations demonstrate significant differences in the simulated precipitation and low clouds. Convective parameterization is found to be a key factor responsible for these differences. Compared with PhysC, parameterized convection of PhysW plays a more important role in moisture transport and rainfall formation. The convective parameterization of PhysW also better captures the onset and retreat of rainfall events, but stronger upward moisture transport largely decreases the tropical low clouds in PhysW. These features are in tune with the previous 3D AMIP simulations. Over the typical stratus-to-stratocumulus transition regime such as the Californian coast, shallow convection in PhysW is more prone to be triggered and leads to larger ventilation above the cloud layer, reducing stratocumulus clouds there. These two suites also have intrinsic differences in the interaction between cloud microphysics and other processes, resulting in different time step sensitivities. PhysC tends to generate more stratiform clouds with decreasing time step. This is caused by separate treatment of stratiform cloud condensation and other microphysical processes, leading to a tight interaction with boundary layer turbulence. In PhysW, all the microphysical processes are executed at the same temporal scale, and thus no such time step sensitivity was found.

Xiaohan Li et al.

Status: open (until 05 Apr 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on gmd-2022-283', Anonymous Referee #1, 06 Mar 2023 reply
  • RC2: 'Comment on gmd-2022-283', Anonymous Referee #2, 07 Mar 2023 reply

Xiaohan Li et al.

Xiaohan Li et al.

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Short summary
The weather and climate physics suites used in GRIST-A22.7.28 are compared using single column modeling. The source of their discrepancies in terms of modeling cloud and precipitation is explored. Convective parameterization is found to be a key factor responsible for the differences. The two suites also have intrinsic differences in the interaction between microphysics and other processes, resulting in different cloud features and time step sensitivities.