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Article
The Impacts of Using Mixed Physics in the Community Leveraged Unified Ensemble
Weather and Forecasting
  • William A. Gallus, Jr., Iowa State University
  • Jamie Wolff, National Center for Atmospheric Research
  • John Halley Gotway, National Center for Atmospheric Research
  • Michelle Harrold, National Center for Atmospheric Research
  • Lindsay Blank, National Center for Atmospheric Research
  • Jeff Beck, Cooperative Institute for Research in the Atmosphere
Document Type
Article
Disciplines
Publication Version
Published Version
Publication Date
8-1-2019
DOI
10.1175/WAF-D-18-0197.1
Abstract

A well-known problem in high-resolution ensembles has been a lack of sufficient spread among members. Modelers often have used mixed physics to increase spread, but this can introduce problems including computational expense, clustering of members, and members that are not all equally skillful. Thus, a detailed examination of the impacts of using mixed physics is important. The present study uses two years of Community Leveraged Unified Ensemble (CLUE) output to isolate the impact of mixed physics in 36-h forecasts made using a convection-permitting ensemble with 3-km horizontal grid spacing. One 10-member subset of the CLUE used only perturbed initial conditions (ICs) and lateral boundary conditions (LBCs) while another 10-member ensemble used the same mixed ICs and LBCs but also introduced mixed physics. The cases examined occurred during NOAA’s Hazardous Weather Testbed Spring Forecast Experiments in 2016 and 2017. Traditional gridpoint metrics applied to each member and the ensemble as a whole, along with object-based verification statistics for all members, were computed for composite reflectivity and 1- and 3-h accumulated precipitation using the Model Evaluation Tools (MET) software package. It is found that the mixed physics increases variability substantially among the ensemble members, more so for reflectivity than precipitation, such that the envelope of members is more likely to encompass the observations. However, the increased variability is mostly due to the introduction of both substantial high biases in members using one microphysical scheme, and low biases in other schemes. Overall ensemble skill is not substantially different from the ensemble using a single physics package.

Comments

This article is published as Gallus Jr, William A., Jamie Wolff, John Halley Gotway, Michelle Harrold, Lindsay Blank, and Jeff Beck. "The Impacts of Using Mixed Physics in the Community Leveraged Unified Ensemble." Weather and Forecasting 34, no. 4 (2019): 849-867. DOI: 10.1175/WAF-D-18-0197.1.

Rights
Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.
Language
en
File Format
application/pdf
Citation Information
William A. Gallus, Jamie Wolff, John Halley Gotway, Michelle Harrold, et al.. "The Impacts of Using Mixed Physics in the Community Leveraged Unified Ensemble" Weather and Forecasting Vol. 34 Iss. 4 (2019) p. 849 - 867
Available at: http://works.bepress.com/william_gallus/79/