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Title: Effects of a Simple Convective Organization Scheme in a Two-Plume GCM

Abstract

A set of experiments is described with the Community Atmosphere Model (CAM5) using a two-plume convection scheme. To represent the differences of organized convection from General Circulation Model (GCM) assumptions of isolated plumes in uniform environments, a dimensionless prognostic “organization” tracer Ω is invoked to lend the second plume a buoyancy advantage relative to the first, as described in Mapes and Neale (2016). When low-entrainment plumes are unconditionally available (Ω = 1 everywhere), deep convection occurs too easily, with consequences including premature (upstream) rainfall in inflows to the deep tropics, excessive convective versus large-scale rainfall, poor relationships to the vapor field, stable bias in the mean state, weak and poor tropical variability, and midday peak in diurnal rainfall over land. Some of these are shown to also be characteristic of CAM4 with its separated deep and shallow convection schemes. When low-entrainment plumes are forbidden by setting Ω = 0 everywhere, some opposite problems can be discerned. In between those extreme cases, an interactive Ω driven by the evaporation of precipitation acts as a local positive feedback loop, concentrating deep convection: In areas of little recent rain, only highly entraining plumes can occur, unfavorable for rain production. This tunable mechanism steadilymore » increases precipitation variance in both space and time, as illustrated here with maps, time-longitude series, and spectra, while avoiding some mean state biases as illustrated with process-oriented diagnostics such as conserved variable profiles and vapor-binned precipitation curves.« less

Authors:
ORCiD logo [1]; ORCiD logo [2]
  1. Texas A & M Univ., Corpus Christi, TX (United States). Dept. of Mathematics and Statistics
  2. Univ. of Miami, FL (United States). Rosenstiel School of Marine and Atmospheric Sciences
Publication Date:
Research Org.:
Univ. of Miami, FL (United States); Texas A & M Univ., Corpus Christi, TX (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); Office of Naval Research (ONR) (United States)
OSTI Identifier:
1430570
Alternate Identifier(s):
OSTI ID: 1430572; OSTI ID: 1511568
Grant/Contract Number:  
SC0000823; SC0006806; N000141310704; DE‐SC0000823; DE‐SC0006806
Resource Type:
Published Article
Journal Name:
Journal of Advances in Modeling Earth Systems
Additional Journal Information:
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; parameterization of convective organization; evaporation of precipitation; entrainment rate; mean state bias; variability

Citation Formats

Chen, Baohua, and Mapes, Brian E. Effects of a Simple Convective Organization Scheme in a Two-Plume GCM. United States: N. p., 2017. Web. doi:10.1002/2017ms001106.
Chen, Baohua, & Mapes, Brian E. Effects of a Simple Convective Organization Scheme in a Two-Plume GCM. United States. doi:10.1002/2017ms001106.
Chen, Baohua, and Mapes, Brian E. Wed . "Effects of a Simple Convective Organization Scheme in a Two-Plume GCM". United States. doi:10.1002/2017ms001106.
@article{osti_1430570,
title = {Effects of a Simple Convective Organization Scheme in a Two-Plume GCM},
author = {Chen, Baohua and Mapes, Brian E.},
abstractNote = {A set of experiments is described with the Community Atmosphere Model (CAM5) using a two-plume convection scheme. To represent the differences of organized convection from General Circulation Model (GCM) assumptions of isolated plumes in uniform environments, a dimensionless prognostic “organization” tracer Ω is invoked to lend the second plume a buoyancy advantage relative to the first, as described in Mapes and Neale (2016). When low-entrainment plumes are unconditionally available (Ω = 1 everywhere), deep convection occurs too easily, with consequences including premature (upstream) rainfall in inflows to the deep tropics, excessive convective versus large-scale rainfall, poor relationships to the vapor field, stable bias in the mean state, weak and poor tropical variability, and midday peak in diurnal rainfall over land. Some of these are shown to also be characteristic of CAM4 with its separated deep and shallow convection schemes. When low-entrainment plumes are forbidden by setting Ω = 0 everywhere, some opposite problems can be discerned. In between those extreme cases, an interactive Ω driven by the evaporation of precipitation acts as a local positive feedback loop, concentrating deep convection: In areas of little recent rain, only highly entraining plumes can occur, unfavorable for rain production. This tunable mechanism steadily increases precipitation variance in both space and time, as illustrated here with maps, time-longitude series, and spectra, while avoiding some mean state biases as illustrated with process-oriented diagnostics such as conserved variable profiles and vapor-binned precipitation curves.},
doi = {10.1002/2017ms001106},
journal = {Journal of Advances in Modeling Earth Systems},
number = 3,
volume = 10,
place = {United States},
year = {2017},
month = {12}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1002/2017ms001106

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Cited by: 1 work
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