Campus Units

Geological and Atmospheric Sciences, Environmental Science, Human Computer Interaction

Document Type

Article

Publication Version

Published Version

Publication Date

8-1-2019

Journal or Book Title

Weather and Forecasting

Volume

34

Issue

4

First Page

849

Last Page

867

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

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