The U.S. Air Force Weather Agency’s mesoscale ensemble: scientific description and performance results
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Authors
Hacker, J.P.
Ha, S.-Y.
Snyder, C.
Berner, J.
Eckel, F.A.
Kuchera, E.
Pocernich, M.
Rugg, S.
Schramm, J.
Wang, X.
Subjects
Advisors
Date of Issue
2011
Date
Publisher
Language
Abstract
This work evaluates several techniques to account for mesoscale initial-condition (IC) and model uncertainty in a
short-range ensemble prediction system based on the Weather Research and Forecast (WRF) model. A scientific
description and verification of several candidate methods for implementation in the U.S. Air Force Weather Agency
mesoscale ensemble is presented. Model perturbation methods tested include multiple parametrization suites, landsurface
property perturbations, perturbations to parameters within physics schemes and stochastic ‘backscatter’ streamfunction
perturbations. IC perturbations considered include perturbed observations in 10 independent WRF-3DVar
cycles and the ensemble-transform Kalman filter (ETKF). A hybrid of ETKF (for IC perturbations) and WRF-3DVar
(to update the ensemble mean) is also tested. Results show that all of the model and IC perturbation methods examined
are more skilful than direct dynamical downscaling of the global ensemble. IC perturbations are most helpful during
the first 12 h of the forecasts. Physical parametrization diversity appears critical for boundary-layer forecasts. In an
effort to reduce system complexity by reducing the number of suites of physical parametrizations, a smaller set of
parametrization suites was combined with perturbed parameters and stochastic backscatter, resulting in the most skilful
and statistically consistent ensemble predictions.
Type
Article
Description
The article of record as published may be located at http://dx.doi.org/10.1111/j.1600-0870.2010.00497.x
Series/Report No
Department
Meteorology
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NPS Report Number
Sponsors
Funding
This work was funded by the U.S. Air Force Weather Agency.
Format
Citation
Tellus (2011), 63A, pp. 625–641
Distribution Statement
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.