Improving the Simulation of Tropical Convective Cloud-Top Heights in CAM5 with CloudSat Observations

Wang, Mingcheng; Zhang, Guang J.

doi:10.1175/JCLI-D-18-0027.1

Title: Improving the Simulation of Tropical Convective Cloud-Top Heights in CAM5 with CloudSat Observations

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Abstract

Using 4 years of CloudSat data, the simulation of tropical convective cloud-top heights (CCTH) above 6 km simulated by the convection scheme in the Community Atmosphere Model, version 5 (CAM5), is evaluated. Compared to CloudSat observations, CAM5 underestimates CCTH by more than 2 km on average. Further analysis of model results suggests that the dilute CAPE calculation, which has been incorporated into the convective parameterization since CAM4, is a main factor restricting CCTH to much lower levels. After removing this restriction, more convective clouds develop into higher altitudes, although convective clouds with tops above 12 km are still underestimated significantly. The environmental conditions under which convection develops in CAM5 are compared with CloudSat observations for convection with similar CCTHs. It is shown that the model atmosphere is much more unstable compared to CloudSat observations, and there is too much entrainment in CAM5. Since CCTHs are closely associated with cloud radiative forcing, the impacts of CCTH on model simulation are further investigated. Results show that the change of CCTH has important impacts on cloud radiative forcing and precipitation. With increased CCTHs, there is more cloud radiative forcing in tropical Africa and the eastern Pacific, but less cloud radiative forcing in themore »« less

Authors:

Wang, Mingcheng ^[1]; Zhang, Guang J. ^[2]

Ministry of Education Key Laboratory for Earth System Modeling, Department of Earth System Science, Tsinghua University, and Joint Center for Global Change Studies, Beijing, China
Scripps Institution of Oceanography, La Jolla, California, and Department of Earth System Science, Tsinghua University, Beijing, China

Publication Date:: Sun Jul 01 00:00:00 EDT 2018

Research Org.:: Univ. of California, San Diego, CA (United States)

Sponsoring Org.:: USDOE Office of Science (SC)

OSTI Identifier:: 1440806

Alternate Identifier(s):: OSTI ID: 1541853

Grant/Contract Number:: SC0016504

Resource Type:: Published Article

Journal Name:: Journal of Climate

Additional Journal Information:: Journal Name: Journal of Climate Journal Volume: 31 Journal Issue: 13; Journal ID: ISSN 0894-8755

Publisher:: American Meteorological Society

Country of Publication:: United States

Language:: English

Subject:: 54 ENVIRONMENTAL SCIENCES; Meteorology & Atmospheric Sciences

Citation Formats


                    Wang, Mingcheng, and Zhang, Guang J. Improving the Simulation of Tropical Convective Cloud-Top Heights in CAM5 with CloudSat Observations.  United States: N. p., 2018. 
Web.  doi:10.1175/JCLI-D-18-0027.1.

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                    Wang, Mingcheng, & Zhang, Guang J. Improving the Simulation of Tropical Convective Cloud-Top Heights in CAM5 with CloudSat Observations.  United States.  https://doi.org/10.1175/JCLI-D-18-0027.1

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                    Wang, Mingcheng, and Zhang, Guang J. Sun .  
"Improving the Simulation of Tropical Convective Cloud-Top Heights in CAM5 with CloudSat Observations".  United States.  https://doi.org/10.1175/JCLI-D-18-0027.1.

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@article{osti_1440806,

  title        = {Improving the Simulation of Tropical Convective Cloud-Top Heights in CAM5 with CloudSat Observations},

  author       = {Wang, Mingcheng and Zhang, Guang J.},

  abstractNote = {Using 4 years of CloudSat data, the simulation of tropical convective cloud-top heights (CCTH) above 6 km simulated by the convection scheme in the Community Atmosphere Model, version 5 (CAM5), is evaluated. Compared to CloudSat observations, CAM5 underestimates CCTH by more than 2 km on average. Further analysis of model results suggests that the dilute CAPE calculation, which has been incorporated into the convective parameterization since CAM4, is a main factor restricting CCTH to much lower levels. After removing this restriction, more convective clouds develop into higher altitudes, although convective clouds with tops above 12 km are still underestimated significantly. The environmental conditions under which convection develops in CAM5 are compared with CloudSat observations for convection with similar CCTHs. It is shown that the model atmosphere is much more unstable compared to CloudSat observations, and there is too much entrainment in CAM5. Since CCTHs are closely associated with cloud radiative forcing, the impacts of CCTH on model simulation are further investigated. Results show that the change of CCTH has important impacts on cloud radiative forcing and precipitation. With increased CCTHs, there is more cloud radiative forcing in tropical Africa and the eastern Pacific, but less cloud radiative forcing in the western Pacific. The contribution to total convective precipitation from convection with cloud tops above 9 km is also increased substantially.},

  doi          = {10.1175/JCLI-D-18-0027.1},

  journal      = {Journal of Climate},

  number       = 13,

  volume       = 31,

  place        = {United States},

  year         = {Sun Jul 01 00:00:00 EDT 2018},

  month        = {Sun Jul 01 00:00:00 EDT 2018}

}

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