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Title: Semiprognostic test of the Arakawa-Schubert cumulus parameterization using simulated data

Abstract

The Arakawa-Schubert (A-S) cumulus parameterization is evaluated by performing semiprognostic tests against data simulated by a cumulus ensemble model (CEM). The CEM is a two-dimensional cloud model for simulating the formation of an ensemble of cumulus clouds under prescribed large-scale conditions. Three simulations, two with vertical wind shear and one without, are performed with identical (time-varying) large-scale advective effects. Detailed comparisons were made between the results of simulation and parameterization. The results include comparisions of surface precipitation rate, apparent heat source, apparent moisture sink, updraft mass flux, and downdraft mass flux. Two different sets of tests were performed. One was the standard A-S parameterization with the cloud work function (CWF) quasi equilibrium, and the other allowed CWF nonequilibrium by accounting for the simulated time change of the CWF. The tests show that the A-S parameterization is valid despite mesoscale organization in cumulus convection. The assumption of CWF quasi equilibrium is more accurate for inputs averaged over smaller subdomain sizes that resolve some mesoscale processes. Errors due to the nondiagnostic aspect of cumulus convection are more significant for inputs averaged over larger subdomain sizes. Errors due to the inherent nondeterministic aspect of cumulus convection appear to be more significant for inputsmore » averaged over smaller subdomain sizes. A modified A-S parameterization with a convective-scale downdraft formulation was also tested against the simulated data. The inclusion of downdrafts slightly improves the results of semiprognostic tests. The impact of downdrafts on the subcloud layer may depend significantly on the subdomain size. 20 refs., 16 figs.« less

Authors:
;  [1]
  1. Univ. of California, Los Angeles (United States)
Publication Date:
OSTI Identifier:
7065252
DOE Contract Number:  
FG02-92ER61363
Resource Type:
Journal Article
Journal Name:
Journal of the Atmospheric Sciences; (United States)
Additional Journal Information:
Journal Volume: 49:24; Journal ID: ISSN 0022-4928
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; ATMOSPHERIC CIRCULATION; FORECASTING; CLOUDS; DYNAMICS; ADVECTION; ATMOSPHERIC PRECIPITATIONS; CLIMATE MODELS; CONVECTION; DATA; HEAT; MOISTURE; SHEAR; SIMULATION; TWO-DIMENSIONAL CALCULATIONS; WIND; ENERGY; ENERGY TRANSFER; HEAT TRANSFER; INFORMATION; MASS TRANSFER; MATHEMATICAL MODELS; MECHANICS; 540110*

Citation Formats

Xu, Kuan-Man, and Arakawa, Aki. Semiprognostic test of the Arakawa-Schubert cumulus parameterization using simulated data. United States: N. p., 1992. Web.
Xu, Kuan-Man, & Arakawa, Aki. Semiprognostic test of the Arakawa-Schubert cumulus parameterization using simulated data. United States.
Xu, Kuan-Man, and Arakawa, Aki. 1992. "Semiprognostic test of the Arakawa-Schubert cumulus parameterization using simulated data". United States.
@article{osti_7065252,
title = {Semiprognostic test of the Arakawa-Schubert cumulus parameterization using simulated data},
author = {Xu, Kuan-Man and Arakawa, Aki},
abstractNote = {The Arakawa-Schubert (A-S) cumulus parameterization is evaluated by performing semiprognostic tests against data simulated by a cumulus ensemble model (CEM). The CEM is a two-dimensional cloud model for simulating the formation of an ensemble of cumulus clouds under prescribed large-scale conditions. Three simulations, two with vertical wind shear and one without, are performed with identical (time-varying) large-scale advective effects. Detailed comparisons were made between the results of simulation and parameterization. The results include comparisions of surface precipitation rate, apparent heat source, apparent moisture sink, updraft mass flux, and downdraft mass flux. Two different sets of tests were performed. One was the standard A-S parameterization with the cloud work function (CWF) quasi equilibrium, and the other allowed CWF nonequilibrium by accounting for the simulated time change of the CWF. The tests show that the A-S parameterization is valid despite mesoscale organization in cumulus convection. The assumption of CWF quasi equilibrium is more accurate for inputs averaged over smaller subdomain sizes that resolve some mesoscale processes. Errors due to the nondiagnostic aspect of cumulus convection are more significant for inputs averaged over larger subdomain sizes. Errors due to the inherent nondeterministic aspect of cumulus convection appear to be more significant for inputs averaged over smaller subdomain sizes. A modified A-S parameterization with a convective-scale downdraft formulation was also tested against the simulated data. The inclusion of downdrafts slightly improves the results of semiprognostic tests. The impact of downdrafts on the subcloud layer may depend significantly on the subdomain size. 20 refs., 16 figs.},
doi = {},
url = {https://www.osti.gov/biblio/7065252}, journal = {Journal of the Atmospheric Sciences; (United States)},
issn = {0022-4928},
number = ,
volume = 49:24,
place = {United States},
year = {Tue Dec 15 00:00:00 EST 1992},
month = {Tue Dec 15 00:00:00 EST 1992}
}