Impact of assimilating radar data using a hybrid 4DEnVar approach on prediction of convective events

This study developed a hybrid four-dimensional (4D) ensemble–variational (4DEnVar) radar data assimilation (DA) system for the Weather Research and Forecasting model. The 4DEnVar approach incorporated ensemble covariances at multiple time levels to assimilate observations distributed in the assimila...

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Autores principales:	Shibo Gao, Ningzhu Du, Jinzhong Min, Haiqiu Yu
Formato:	article
Lenguaje:	EN
Publicado:	Taylor & Francis Group 2021
Materias:	4denvar 3denvar radar data assimilation convective forecasting Oceanography GC1-1581 Meteorology. Climatology QC851-999
Acceso en línea:	https://doaj.org/article/275c095559444d7584ce591d4e9e5813
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spelling	oai:doaj.org-article:275c095559444d7584ce591d4e9e58132021-12-01T14:40:58ZImpact of assimilating radar data using a hybrid 4DEnVar approach on prediction of convective events1600-087010.1080/16000870.2021.1903770https://doaj.org/article/275c095559444d7584ce591d4e9e58132021-01-01T00:00:00Zhttp://dx.doi.org/10.1080/16000870.2021.1903770https://doaj.org/toc/1600-0870This study developed a hybrid four-dimensional (4D) ensemble–variational (4DEnVar) radar data assimilation (DA) system for the Weather Research and Forecasting model. The 4DEnVar approach incorporated ensemble covariances at multiple time levels to assimilate observations distributed in the assimilation windows. By approximating the evolution of the background error using 4D ensemble covariance, use of the tangent linear and adjoint models was avoided. The impact of 4DEnVar radar DA on convective-scale analyses and forecasts was examined through comparison with 3DVar and 3DEnVar methods for the case of a squall line that occurred over southeastern China. In comparison with the other methods, 4DEnVar produced both smaller root mean square innovations for radar reflectivity and radial velocity and better analysis of the vertical structure of reflectivity. The corresponding relative humidity and vertical wind in convective regions were strengthened. Ultimately, 4DEnVar produced a substantially improved forecast, including improved quantitative precipitation and reflectivity forecast skill, and better representation of the squall line in terms of both areal coverage and intensity. In contrast, 3DEnVar improved the analysis and forecast modestly in comparison with 3DVar. Furthermore, sensitivity experiments indicated that a moderate assimilation window and a stronger ensemble weighting factor used in 4DEnVar could produce superior forecast results. The wind, temperature and water vapor were also improved by 4DEnVar, with the largest bias reduction for water vapor at low and middle levels. The improvements of 4DEnVar were further verified and shown effective using a mesocale convective system case and a local convection case.Shibo GaoNingzhu DuJinzhong MinHaiqiu YuTaylor & Francis Grouparticle4denvar3denvarradar data assimilationconvective forecastingOceanographyGC1-1581Meteorology. ClimatologyQC851-999ENTellus: Series A, Dynamic Meteorology and Oceanography, Vol 73, Iss 1, Pp 1-19 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	4denvar 3denvar radar data assimilation convective forecasting Oceanography GC1-1581 Meteorology. Climatology QC851-999
spellingShingle	4denvar 3denvar radar data assimilation convective forecasting Oceanography GC1-1581 Meteorology. Climatology QC851-999 Shibo Gao Ningzhu Du Jinzhong Min Haiqiu Yu Impact of assimilating radar data using a hybrid 4DEnVar approach on prediction of convective events
description	This study developed a hybrid four-dimensional (4D) ensemble–variational (4DEnVar) radar data assimilation (DA) system for the Weather Research and Forecasting model. The 4DEnVar approach incorporated ensemble covariances at multiple time levels to assimilate observations distributed in the assimilation windows. By approximating the evolution of the background error using 4D ensemble covariance, use of the tangent linear and adjoint models was avoided. The impact of 4DEnVar radar DA on convective-scale analyses and forecasts was examined through comparison with 3DVar and 3DEnVar methods for the case of a squall line that occurred over southeastern China. In comparison with the other methods, 4DEnVar produced both smaller root mean square innovations for radar reflectivity and radial velocity and better analysis of the vertical structure of reflectivity. The corresponding relative humidity and vertical wind in convective regions were strengthened. Ultimately, 4DEnVar produced a substantially improved forecast, including improved quantitative precipitation and reflectivity forecast skill, and better representation of the squall line in terms of both areal coverage and intensity. In contrast, 3DEnVar improved the analysis and forecast modestly in comparison with 3DVar. Furthermore, sensitivity experiments indicated that a moderate assimilation window and a stronger ensemble weighting factor used in 4DEnVar could produce superior forecast results. The wind, temperature and water vapor were also improved by 4DEnVar, with the largest bias reduction for water vapor at low and middle levels. The improvements of 4DEnVar were further verified and shown effective using a mesocale convective system case and a local convection case.
format	article
author	Shibo Gao Ningzhu Du Jinzhong Min Haiqiu Yu
author_facet	Shibo Gao Ningzhu Du Jinzhong Min Haiqiu Yu
author_sort	Shibo Gao
title	Impact of assimilating radar data using a hybrid 4DEnVar approach on prediction of convective events
title_short	Impact of assimilating radar data using a hybrid 4DEnVar approach on prediction of convective events
title_full	Impact of assimilating radar data using a hybrid 4DEnVar approach on prediction of convective events
title_fullStr	Impact of assimilating radar data using a hybrid 4DEnVar approach on prediction of convective events
title_full_unstemmed	Impact of assimilating radar data using a hybrid 4DEnVar approach on prediction of convective events
title_sort	impact of assimilating radar data using a hybrid 4denvar approach on prediction of convective events
publisher	Taylor & Francis Group
publishDate	2021
url	https://doaj.org/article/275c095559444d7584ce591d4e9e5813
work_keys_str_mv	AT shibogao impactofassimilatingradardatausingahybrid4denvarapproachonpredictionofconvectiveevents AT ningzhudu impactofassimilatingradardatausingahybrid4denvarapproachonpredictionofconvectiveevents AT jinzhongmin impactofassimilatingradardatausingahybrid4denvarapproachonpredictionofconvectiveevents AT haiqiuyu impactofassimilatingradardatausingahybrid4denvarapproachonpredictionofconvectiveevents
_version_	1718405046270427136

Impact of assimilating radar data using a hybrid 4DEnVar approach on prediction of convective events

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