Impact of a digital filter as a weak constraint in MM5 4DVAR: An observing system simulation experiment
In this study, a digital filter is introduced into the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM5) four-dimensional variational data assimilation (4DVAR) system as a weak constraint to control high-frequency oscillations, which negati...
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ftncar:oai:drupal-site.org:articles_17329 2023-09-05T13:13:06+02:00 Impact of a digital filter as a weak constraint in MM5 4DVAR: An observing system simulation experiment Wee, Tae-Kwon (author) Bromwich, David (contributor) Kuo, Ying-Hwa (author) Schreiner, William (contributor) Huang, Xiang-Yu (contributor) Guo, Yong-Run (contributor) Xiao, Qingnong (contributor) Moore, Ingrid (contributor) Conrad, Kristin (contributor) 2004-02-01 application/pdf http://nldr.library.ucar.edu/repository/collections/OSGC-000-000-001-432 https://doi.org/10.1175/1520-0493(2004)132<0543:IOADFA>2.0.CO;2 en eng American Meteorological Society Monthly Weather Review http://nldr.library.ucar.edu/repository/collections/OSGC-000-000-001-432 doi:10.1175/1520-0493(2004)132<0543:IOADFA>2.0.CO;2 ark:/85065/d7pg1t0g Copyright 2004 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be "fair use" under Section 107 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Law (17 USC, as revised by P.L. 94-553) does not require the Society's permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statements, requires written permission or license from the AMS. Additional details are provided in the AMS Copyright Policies, available from the AMS at 617-227-2425 or amspubs@ametsoc.org. Permission to place a copy of this work on this server has been provided by the AMS. The AMS does not guarantee that the copy provided here is an accurate copy of the published work. Text article 2004 ftncar https://doi.org/10.1175/1520-0493(2004)132<0543:IOADFA>2.0.CO;2 2023-08-14T18:44:25Z In this study, a digital filter is introduced into the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM5) four-dimensional variational data assimilation (4DVAR) system as a weak constraint to control high-frequency oscillations, which negatively affect assimilation performance. To assess the impact of the digital filter and to understand how the digital-filter 4DVAR functions, a series of observing system simulation experiments are conducted with the assimilation of global positioning system (GPS) refractivity soundings for a cyclogenesis case over the Antarctic region. It is shown that the use of a digital filter, centered at the midpoint of the assimilation period, is effective in suppressing the high-frequency waves. The imbalance during the early period of assimilation is further reduced by utilizing an additional short-span filter, starting at the beginning of the assimilation period. The filtering of the wind field is found to be the most effective in suppressing high-frequency oscillations. It is also revealed that the imposed weak constraint significantly reduces the wave-reflection problem caused by imperfect upper boundary conditions. It is concluded that the weakly constrained 4DVAR with digital filters not only reduces dynamic imbalance, but also significantly improves the qualities of analysis and forecast. Without projecting its solution onto the high-frequency waves, which diminish rapidly with forecast time, the constrained 4DVAR is able to yield additional improvement in the model initial condition in the larger-scale range and hence utilizes the available observations more effectively when compared with the unconstrained 4DVAR. Article in Journal/Newspaper Antarc* Antarctic OpenSky (NCAR/UCAR - National Center for Atmospheric Research/University Corporation for Atmospheric Research) Antarctic The Antarctic |
institution |
Open Polar |
collection |
OpenSky (NCAR/UCAR - National Center for Atmospheric Research/University Corporation for Atmospheric Research) |
op_collection_id |
ftncar |
language |
English |
description |
In this study, a digital filter is introduced into the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM5) four-dimensional variational data assimilation (4DVAR) system as a weak constraint to control high-frequency oscillations, which negatively affect assimilation performance. To assess the impact of the digital filter and to understand how the digital-filter 4DVAR functions, a series of observing system simulation experiments are conducted with the assimilation of global positioning system (GPS) refractivity soundings for a cyclogenesis case over the Antarctic region. It is shown that the use of a digital filter, centered at the midpoint of the assimilation period, is effective in suppressing the high-frequency waves. The imbalance during the early period of assimilation is further reduced by utilizing an additional short-span filter, starting at the beginning of the assimilation period. The filtering of the wind field is found to be the most effective in suppressing high-frequency oscillations. It is also revealed that the imposed weak constraint significantly reduces the wave-reflection problem caused by imperfect upper boundary conditions. It is concluded that the weakly constrained 4DVAR with digital filters not only reduces dynamic imbalance, but also significantly improves the qualities of analysis and forecast. Without projecting its solution onto the high-frequency waves, which diminish rapidly with forecast time, the constrained 4DVAR is able to yield additional improvement in the model initial condition in the larger-scale range and hence utilizes the available observations more effectively when compared with the unconstrained 4DVAR. |
author2 |
Wee, Tae-Kwon (author) Bromwich, David (contributor) Kuo, Ying-Hwa (author) Schreiner, William (contributor) Huang, Xiang-Yu (contributor) Guo, Yong-Run (contributor) Xiao, Qingnong (contributor) Moore, Ingrid (contributor) Conrad, Kristin (contributor) |
format |
Article in Journal/Newspaper |
title |
Impact of a digital filter as a weak constraint in MM5 4DVAR: An observing system simulation experiment |
spellingShingle |
Impact of a digital filter as a weak constraint in MM5 4DVAR: An observing system simulation experiment |
title_short |
Impact of a digital filter as a weak constraint in MM5 4DVAR: An observing system simulation experiment |
title_full |
Impact of a digital filter as a weak constraint in MM5 4DVAR: An observing system simulation experiment |
title_fullStr |
Impact of a digital filter as a weak constraint in MM5 4DVAR: An observing system simulation experiment |
title_full_unstemmed |
Impact of a digital filter as a weak constraint in MM5 4DVAR: An observing system simulation experiment |
title_sort |
impact of a digital filter as a weak constraint in mm5 4dvar: an observing system simulation experiment |
publisher |
American Meteorological Society |
publishDate |
2004 |
url |
http://nldr.library.ucar.edu/repository/collections/OSGC-000-000-001-432 https://doi.org/10.1175/1520-0493(2004)132<0543:IOADFA>2.0.CO;2 |
geographic |
Antarctic The Antarctic |
geographic_facet |
Antarctic The Antarctic |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_relation |
Monthly Weather Review http://nldr.library.ucar.edu/repository/collections/OSGC-000-000-001-432 doi:10.1175/1520-0493(2004)132<0543:IOADFA>2.0.CO;2 ark:/85065/d7pg1t0g |
op_rights |
Copyright 2004 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be "fair use" under Section 107 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Law (17 USC, as revised by P.L. 94-553) does not require the Society's permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statements, requires written permission or license from the AMS. Additional details are provided in the AMS Copyright Policies, available from the AMS at 617-227-2425 or amspubs@ametsoc.org. Permission to place a copy of this work on this server has been provided by the AMS. The AMS does not guarantee that the copy provided here is an accurate copy of the published work. |
op_doi |
https://doi.org/10.1175/1520-0493(2004)132<0543:IOADFA>2.0.CO;2 |
_version_ |
1776203449105383424 |