Parameterizing Convective Organization Effects With a Moisture-PDF Approach in Climate Models: Concept and a Regional Case Simulation

Journal Article · 15 May 2022 · Journal of Advances in Modeling Earth Systems

DOI: https://doi.org/10.1029/2021ms002942 · OSTI ID:1869246

Yang, Ben  ^[1]; Wang, Minghuai  ^[1]; Zhang, Guang J.  ^[2]; Guo, Zhun  ^[3]; Wang, Yong ^[4]; Xu, Xin  ^[1]; Dai, Guoqing ^[1]; Huang, Anning  ^[1]; Zhang, Yaocun  ^[1]; Qian, Yun  ^[5]

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1. Nanjing Univ. (China)
2. Univ. of California, San Diego, La Jolla, CA (United States)
3. Chinese Academy of Sciences (CAS), Beijing (China)
4. Tsinghua Univ., Beijing (China)
5. Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)

We propose a parameterization scheme of convective organization effects based on a moisture-distribution approach, which can reflect aggregation of convective cells within a model grid as well as the interaction between convection and spatial heterogeneity in free-troposphere moisture. With this concept, convective cells in an aggregated state are surrounded by air that is moister than the grid-mean condition, which provides a “shielding” effect favorable for deeper convective updrafts. Such effects are represented quantitatively via utilizing a schematic diagram about the geometric interpretation of convective cluster, dry area, and their contact area, in which both the convective cluster size and dry area fraction increase during the development of convection. Our sensitivity analyses indicate that the new scheme performs well in capturing the mean precipitation features. Excluding the convective organization effects in the model leads to a considerable reduction in the simulated precipitation magnitude. Notably, there exists an inverse relationship between background mean moisture condition and sub-grid moisture variability for a given rain rate, suggesting that with a high spatial heterogeneity in free-troposphere moisture, convection can still develop and maintain its strength under relatively dry background conditions, consistent with the convection-permitting model simulation. Overall, our new parameterization of convective organization effects can successfully reproduce the relationship between precipitation and sub-grid moisture variability, which is a missing element in traditional convection parameterization schemes but important for the simulations of precipitation variability at various scales in climate models.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Atmospheric Radiation Measurement (ARM) Data Center; Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
• Sponsoring Organization: Fundamental Research Funds for the Central Universities; National Key Research and Development Program; National Natural Science Foundation of China (NSFC); USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Contributing Organization: Argonne National Laboratory (ANL); Brookhaven National Laboratory (BNL); Oak Ridge National Laboratory (ORNL); Pacific Northwest National Laboratory (PNNL)
• Grant/Contract Number: AC05-76RL01830; SC0022064
• OSTI ID: 1869246
• Report Number(s): PNNL-SA--179211
• Journal Information: Journal of Advances in Modeling Earth Systems, Journal Name: Journal of Advances in Modeling Earth Systems Journal Issue: 5 Vol. 14; ISSN 1942-2466
• Publisher: American Geophysical Union (AGU)Copyright Statement
• Country of Publication: United States
• Language: English