skip to main content
DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

This content will become publicly available on December 1, 2021

Title: Impacts of Stochastic Mixing in Idealized Convection-Permitting Simulations of Squall Lines

Abstract

This study investigates impacts of altering subgrid-scale mixing in “convection-permitting” kilometer-scale horizontal-grid-spacing (Δh) simulations by applying either constant or stochastic multiplicative factors to the horizontal mixing coefficients within the Weather Research and Forecasting Model. In quasi-idealized 1-km Δh simulations of two observationally based squall-line cases, constant enhanced mixing produces larger updraft cores that are more dilute at upper levels, weakens the cold pool, rear-inflow jet, and front-to-rear flow of the squall line, and degrades the model’s effective resolution. Reducing mixing by a constant multiplicative factor has the opposite effect on all metrics. Completely turning off parameterized horizontal mixing produces bulk updraft statistics and squall-line mesoscale structure closest to an LES “benchmark” among all 1-km simulations, although the updraft cores are too undilute. The stochastic mixing scheme, which applies a multiplicative factor to the mixing coefficients that varies stochastically in time and space, is employed at 0.5-, 1-, and 2-km Δh. It generally reduces midlevel vertical velocities and enhances upper-level vertical velocities compared to simulations using the standard mixing scheme, with more substantial impacts at 1- and 2-km Δh compared to 0.5-km Δh. Further, the stochastic scheme also increases updraft dilution to better agree with the LES for one case, butmore » has less impact on the other case. Stochastic mixing acts to weaken the cold pool but without a significant impact on squall-line propagation. It also does not affect the model’s overall effective resolution unlike applying constant multiplicative factors to the mixing coefficients.« less

Authors:
 [1];  [2];  [3]
  1. a University of Utah, Salt Lake City, Utah
  2. b National Center for Atmospheric Research, Boulder, Colorado
  3. a University of Utah, Salt Lake City, Utah;c Pacific Northwest National Laboratory, Richland, Washington
Publication Date:
Research Org.:
National Center for Atmospheric Research (NCAR), Boulder, CO (United States); Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER)
OSTI Identifier:
1786978
Alternate Identifier(s):
OSTI ID: 1735951
Report Number(s):
PNNL-SA-156541
Journal ID: ISSN 0027-0644
Grant/Contract Number:  
SC0016476; AC05-76RL01830
Resource Type:
Accepted Manuscript
Journal Name:
Monthly Weather Review
Additional Journal Information:
Journal Volume: 148; Journal Issue: 12; Journal ID: ISSN 0027-0644
Publisher:
American Meteorological Society
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY

Citation Formats

Stanford, McKenna W., Morrison, Hugh, and Varble, Adam. Impacts of Stochastic Mixing in Idealized Convection-Permitting Simulations of Squall Lines. United States: N. p., 2020. Web. https://doi.org/10.1175/mwr-d-20-0135.1.
Stanford, McKenna W., Morrison, Hugh, & Varble, Adam. Impacts of Stochastic Mixing in Idealized Convection-Permitting Simulations of Squall Lines. United States. https://doi.org/10.1175/mwr-d-20-0135.1
Stanford, McKenna W., Morrison, Hugh, and Varble, Adam. Tue . "Impacts of Stochastic Mixing in Idealized Convection-Permitting Simulations of Squall Lines". United States. https://doi.org/10.1175/mwr-d-20-0135.1. https://www.osti.gov/servlets/purl/1786978.
@article{osti_1786978,
title = {Impacts of Stochastic Mixing in Idealized Convection-Permitting Simulations of Squall Lines},
author = {Stanford, McKenna W. and Morrison, Hugh and Varble, Adam},
abstractNote = {This study investigates impacts of altering subgrid-scale mixing in “convection-permitting” kilometer-scale horizontal-grid-spacing (Δh) simulations by applying either constant or stochastic multiplicative factors to the horizontal mixing coefficients within the Weather Research and Forecasting Model. In quasi-idealized 1-km Δh simulations of two observationally based squall-line cases, constant enhanced mixing produces larger updraft cores that are more dilute at upper levels, weakens the cold pool, rear-inflow jet, and front-to-rear flow of the squall line, and degrades the model’s effective resolution. Reducing mixing by a constant multiplicative factor has the opposite effect on all metrics. Completely turning off parameterized horizontal mixing produces bulk updraft statistics and squall-line mesoscale structure closest to an LES “benchmark” among all 1-km simulations, although the updraft cores are too undilute. The stochastic mixing scheme, which applies a multiplicative factor to the mixing coefficients that varies stochastically in time and space, is employed at 0.5-, 1-, and 2-km Δh. It generally reduces midlevel vertical velocities and enhances upper-level vertical velocities compared to simulations using the standard mixing scheme, with more substantial impacts at 1- and 2-km Δh compared to 0.5-km Δh. Further, the stochastic scheme also increases updraft dilution to better agree with the LES for one case, but has less impact on the other case. Stochastic mixing acts to weaken the cold pool but without a significant impact on squall-line propagation. It also does not affect the model’s overall effective resolution unlike applying constant multiplicative factors to the mixing coefficients.},
doi = {10.1175/mwr-d-20-0135.1},
journal = {Monthly Weather Review},
number = 12,
volume = 148,
place = {United States},
year = {2020},
month = {12}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Save / Share: