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

Abstract

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 steadily increases precipitation variancemore » 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:

Chen, Baohua  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-1654-0258"

Mapes, Brian E.  ^[2]

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• Search DOE PAGES for ORCID "0000-0001-5460-3761"

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+ Show Author Affiliations

1. Department of Mathematics and Statistics Texas A&,M University at Corpus Christi Corpus Christi TX USA
2. Rosenstiel School of Marine and Atmospheric Sciences University of Miami Miami FL USA

Publication Date:

Fri Mar 30 00:00:00 EDT 2018

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); Office of Naval Research (ONR) (United States)

OSTI Identifier:

1430570

Alternate Identifier(s):

OSTI ID: 1430572; OSTI ID: 1511568

Grant/Contract Number:  

DE‐SC0000823; DE‐SC0006806; SC0000823; SC0006806; N000141310704

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; parameterization of convective organization; evaporation of precipitation; entrainment rate; mean state bias; variability