Title: The Roles of Convection Parameterization in the Formation of Double ITCZ Syndrome in the NCAR CESM: I. Atmospheric Processes

Abstract

Abstract Several improvements are implemented in the Zhang‐McFarlane (ZM) convection scheme to investigate the roles of convection parameterization in the formation of double intertropical convergence zone (ITCZ) bias in the NCAR CESM1.2.1. It is shown that the prominent double ITCZ biases of precipitation, sea surface temperature (SST), and wind stress in the standard CESM1.2.1 are largely eliminated in all seasons with the use of these improvements in convection scheme. This study for the first time demonstrates that the modifications of convection scheme can eliminate the double ITCZ biases in all seasons, including boreal winter and spring. Further analysis shows that the elimination of the double ITCZ bias is achieved not by improving other possible contributors, such as stratus cloud bias off the west coast of South America and cloud/radiation biases over the Southern Ocean, but by modifying the convection scheme itself. This study demonstrates that convection scheme is the primary contributor to the double ITCZ bias in the CESM1.2.1, and provides a possible solution to the long‐standing double ITCZ problem. The atmospheric model simulations forced by observed SST show that the original ZM convection scheme tends to produce double ITCZ bias in high SST scenario, while the modified convection schememore » does not. The impact of changes in each core component of convection scheme on the double ITCZ bias in atmospheric model is identified and further investigated.« less

Authors:

Song, Xiaoliang  ^[1];

• Search DOE PAGES for author "Song, Xiaoliang"
• Search DOE PAGES for ORCID "0000-0003-3113-969X"

Zhang, Guang J.  ^[1]

• Search DOE PAGES for author "Zhang, Guang J."
• Search DOE PAGES for ORCID "0000-0002-9712-5226"

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+ Show Author Affiliations

1. Scripps Institution of Oceanography, University of California San Diego, La Jolla CA USA

Publication Date:

Sun Mar 25 00:00:00 EDT 2018

Research Org.:

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

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1429528

Alternate Identifier(s):

OSTI ID: 1429529; OSTI ID: 1511465

Grant/Contract Number:  

DE‐SC0016504; SC0016504

Resource Type:

Published Article

Journal Name:

Journal of Advances in Modeling Earth Systems

Additional Journal Information:

Journal Name: Journal of Advances in Modeling Earth Systems Journal Volume: 10 Journal Issue: 3; Journal ID: ISSN 1942-2466

Publisher:

American Geophysical Union (AGU)

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; double ITCZ; convection parameterization; spectral cloud model; climate model