Open AccessUnderstanding Cloud and Convective Characteristics in Version 1 of the E3SM Atmosphere Model
Author(s) -
Xie Shaocheng,
Lin Wuyin,
Rasch Philip J.,
Ma PoLun,
Neale Richard,
Larson Vincent E.,
Qian Yun,
Bogenschutz Peter A.,
Caldwell Peter,
CameronSmith Philip,
Golaz JeanChristophe,
Mahajan Salil,
Singh Balwinder,
Tang Qi,
Wang Hailong,
Yoon JinHo,
Zhang Kai,
Zhang Yuying
Publication year - 2018
Publication title -
journal of advances in modeling earth systems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.03
H-Index - 58
ISSN - 1942-2466
DOI - 10.1029/2018ms001350
Subject(s) - environmental science , atmospheric sciences , longwave , convection , liquid water path , precipitation , intertropical convergence zone , atmosphere (unit) , atmospheric model , climatology , climate model , cloud physics , marine stratocumulus , forcing (mathematics) , meteorology , radiative transfer , cloud computing , geology , climate change , physics , computer science , oceanography , quantum mechanics , aerosol , operating system
This study provides comprehensive insight into the notable differences in clouds and precipitation simulated by the Energy Exascale Earth System Model Atmosphere Model version 0 and version 1 (EAMv1). Several sensitivity experiments are conducted to isolate the impact of changes in model physics, resolution, and parameter choices on these differences. The overall improvement in EAMv1 clouds and precipitation is primarily attributed to the introduction of a simplified third‐order turbulence parameterization Cloud Layers Unified By Binormals (along with the companion changes) for a unified treatment of boundary layer turbulence, shallow convection, and cloud macrophysics, though it also leads to a reduction in subtropical coastal stratocumulus clouds. This lack of stratocumulus clouds is considerably improved by increasing vertical resolution from 30 to 72 layers, but the gain is unfortunately subsequently offset by other retuning to reach the top‐of‐atmosphere energy balance. Increasing vertical resolution also results in a considerable underestimation of high clouds over the tropical warm pool, primarily due to the selection for numerical stability of a higher air parcel launch level in the deep convection scheme. Increasing horizontal resolution from 1° to 0.25° without retuning leads to considerable degradation in cloud and precipitation fields, with much weaker tropical and subtropical short‐ and longwave cloud radiative forcing and much stronger precipitation in the intertropical convergence zone, indicating poor scale awareness of the cloud parameterizations. To avoid this degradation, significantly different parameter settings for the low‐resolution (1°) and high‐resolution (0.25°) were required to achieve optimal performance in EAMv1.