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- Title
Incorporating the Effect of Large‐Scale Vertical Motion on Convection Through Convective Mass Flux Adjustment in E3SMv2.
- Authors
Song, Xiaoliang; Zhang, Guang; Wan, Hui; Xie, Shaocheng
- Abstract
Recent observational studies suggest that the large‐scale dynamical forcing (vertical motion) plays important roles in deep convection development. In this study we propose a convective mass flux adjustment (MAdj) approach to represent the dynamical effects of large‐scale vertical motion on convection in the Department of Energy's Energy Exascale Earth System Model version 2 (E3SMv2). With MAdj, convection is enhanced (suppressed) when there is large‐scale ascending (descending) motion at the planetary boundary layer top. The coupling of convection with large‐scale circulation significantly improves the simulation of climate variability in E3SMv2 across multiple scales from the diurnal cycle, convectively coupled equatorial waves, to the Madden‐Julian Oscillation (MJO). The standard E3SMv2 tends to simulate overly weak diurnal amplitude of precipitation and overly weak variance of convectively coupled equatorial Kelvin and westward inertio‐gravity (WIG) waves. It also fails to simulate the essential characteristics of the MJO: continuous eastward propagation. With MAdj, the amplitude of diurnal cycle of precipitation is systematically increased and its probability density distribution is much closer to observations. The MAdj can also simulate more realistic eastward propagation of the MJO and much stronger convectively coupled Kelvin and WIG waves. Moreover, the MAdj approach slightly improves the climatology simulations in precipitation, cloud, radiation, circulation, temperature, and moisture fields, with overall root‐mean‐square error (RMSE) of major climatological fields reduced by about 2%. The MAdj approach suppresses excessive grid‐scale precipitation, reducing precipitation wet biases over South China Sea, Philippine Sea, Himalayas, and South Pacific Convergence Zone in western Pacific in summer. Plain Language Summary: The representation of convection in global climate models is one of the most challenging scientific issues in climate modeling. Many deficiencies in precipitation and climate variability simulations and uncertainties in climate change projections can be traced to the poor representation of convection. Recent observational studies suggest that large‐scale vertical motion plays important roles in deep convection development. In this study we propose a convective mass flux adjustment (MAdj) approach to represent the effects of large‐scale vertical motion on convection in the Department of Energy's Energy Exascale Earth System Model version 2 (E3SMv2). With MAdj, convection is enhanced (suppressed) when there is large‐scale ascending (descending) motion at the planetary boundary layer top. The coupling of convection with large‐scale circulation significantly improves the climate variability simulation of E3SMv2 across multiple scales from the diurnal cycle, convectively coupled equatorial waves, to the Madden‐Julian Oscillation. Improving climate variability simulation through modifying convection parameterization usually causes degradations of the mean state and other climate aspects. The MAdj approach does not degrade the climatology simulations. It actually slightly improves the climatology simulations in precipitation, cloud, radiation, circulation, temperature and moisture fields. Key Points: A convective mass flux adjustment approach is proposed to represent the dynamical effects of large‐scale vertical motion on convectionThe mass flux adjustment significantly improves the climate variability simulation of E3SMv2 across multiple scalesThe mass flux adjustment slightly improves climatology simulations of precipitation, cloud, radiation, circulation, temperature, and moisture
- Subjects
HIMALAYA Mountains; VERTICAL motion; ATMOSPHERIC boundary layer; CLIMATE change models; MADDEN-Julian oscillation; OCEAN waves
- Publication
Journal of Advances in Modeling Earth Systems, 2023, Vol 15, Issue 10, p1
- ISSN
1942-2466
- Publication type
Article
- DOI
10.1029/2022MS003553