Assessment of climate biases in OpenIFS version 43r3 across model horizontal resolutions and time steps
<p>We examine the impact of horizontal resolution and model time step on the climate of the OpenIFS version 43r3 atmospheric general circulation model. A series of simulations for the period 1979–2019 are conducted with various horizontal resolutions (i.e. <span class="inline-formula&q...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2024-02-01
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| Series: | Geoscientific Model Development |
| Online Access: | https://gmd.copernicus.org/articles/17/1813/2024/gmd-17-1813-2024.pdf |
| _version_ | 1827572795608924160 |
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| author | A. Savita J. Kjellsson J. Kjellsson R. Pilch Kedzierski R. Pilch Kedzierski M. Latif M. Latif T. Rahm T. Rahm S. Wahl W. Park W. Park |
| author_facet | A. Savita J. Kjellsson J. Kjellsson R. Pilch Kedzierski R. Pilch Kedzierski M. Latif M. Latif T. Rahm T. Rahm S. Wahl W. Park W. Park |
| author_sort | A. Savita |
| collection | DOAJ |
| description | <p>We examine the impact of horizontal resolution and model time step on the climate of the OpenIFS version 43r3 atmospheric general circulation model. A series of simulations for the period 1979–2019 are conducted with various horizontal resolutions (i.e. <span class="inline-formula">∼100</span>, <span class="inline-formula">∼50</span>, and <span class="inline-formula">∼25</span> km) while maintaining the same time step (i.e. 15 min) and using different time steps (i.e. 60, 30, and 15 min) at 100 km horizontal resolution. We find that the surface zonal wind bias is significantly reduced over certain regions such as the Southern Ocean and the Northern Hemisphere mid-latitudes and in tropical and subtropical regions at a high horizontal resolution (i.e. <span class="inline-formula">∼25</span> km). Similar improvement is evident too when using a coarse-resolution model (<span class="inline-formula">∼100</span> km) with a smaller time step (i.e. 30 and 15 min). We also find improvements in Rossby wave amplitude and phase speed, as well as in weather regime patterns, when a smaller time step or higher horizontal resolution is used. The improvement in the wind bias when using the shorter time step is mostly due to an increase in shallow and mid-level convection that enhances vertical mixing in the lower troposphere. The enhanced mixing allows frictional effects to influence a deeper layer and reduces wind and wind speed throughout the troposphere. However, precipitation biases generally increase with higher horizontal resolutions or smaller time steps, whereas the surface air temperature bias exhibits a small improvement over North America and the eastern Eurasian continent. We argue that the bias improvement in the highest-horizontal-resolution (i.e. <span class="inline-formula">∼25</span> km) configuration benefits from a combination of both the enhanced horizontal resolution and the shorter time step. In summary, we demonstrate that, by reducing the time step in the coarse-resolution (<span class="inline-formula">∼100</span> km) OpenIFS model, one can alleviate some climate biases at a lower cost than by increasing the horizontal resolution.</p> |
| first_indexed | 2024-03-07T19:37:23Z |
| format | Article |
| id | doaj.art-282b98106f9c4d1abbda32ca55812a5f |
| institution | Directory Open Access Journal |
| issn | 1991-959X 1991-9603 |
| language | English |
| last_indexed | 2024-03-07T19:37:23Z |
| publishDate | 2024-02-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Geoscientific Model Development |
| spelling | doaj.art-282b98106f9c4d1abbda32ca55812a5f2024-02-29T07:45:21ZengCopernicus PublicationsGeoscientific Model Development1991-959X1991-96032024-02-01171813182910.5194/gmd-17-1813-2024Assessment of climate biases in OpenIFS version 43r3 across model horizontal resolutions and time stepsA. Savita0J. Kjellsson1J. Kjellsson2R. Pilch Kedzierski3R. Pilch Kedzierski4M. Latif5M. Latif6T. Rahm7T. Rahm8S. Wahl9W. Park10W. Park11GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, GermanyGEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, GermanyFaculty of Mathematics and Natural Sciences, Christian Albrechts University of Kiel, Kiel, GermanyGEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, GermanyMeteorological Institute, Universität Hamburg, Hamburg, GermanyGEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, GermanyFaculty of Mathematics and Natural Sciences, Christian Albrechts University of Kiel, Kiel, GermanyGEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, GermanyFaculty of Mathematics and Natural Sciences, Christian Albrechts University of Kiel, Kiel, GermanyGEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, GermanyCenter for Climate Physics, Institute for Basic Science (IBS), Busan, Republic of KoreaDepartment of Climate System, Pusan National University, Busan, Republic of Korea<p>We examine the impact of horizontal resolution and model time step on the climate of the OpenIFS version 43r3 atmospheric general circulation model. A series of simulations for the period 1979–2019 are conducted with various horizontal resolutions (i.e. <span class="inline-formula">∼100</span>, <span class="inline-formula">∼50</span>, and <span class="inline-formula">∼25</span> km) while maintaining the same time step (i.e. 15 min) and using different time steps (i.e. 60, 30, and 15 min) at 100 km horizontal resolution. We find that the surface zonal wind bias is significantly reduced over certain regions such as the Southern Ocean and the Northern Hemisphere mid-latitudes and in tropical and subtropical regions at a high horizontal resolution (i.e. <span class="inline-formula">∼25</span> km). Similar improvement is evident too when using a coarse-resolution model (<span class="inline-formula">∼100</span> km) with a smaller time step (i.e. 30 and 15 min). We also find improvements in Rossby wave amplitude and phase speed, as well as in weather regime patterns, when a smaller time step or higher horizontal resolution is used. The improvement in the wind bias when using the shorter time step is mostly due to an increase in shallow and mid-level convection that enhances vertical mixing in the lower troposphere. The enhanced mixing allows frictional effects to influence a deeper layer and reduces wind and wind speed throughout the troposphere. However, precipitation biases generally increase with higher horizontal resolutions or smaller time steps, whereas the surface air temperature bias exhibits a small improvement over North America and the eastern Eurasian continent. We argue that the bias improvement in the highest-horizontal-resolution (i.e. <span class="inline-formula">∼25</span> km) configuration benefits from a combination of both the enhanced horizontal resolution and the shorter time step. In summary, we demonstrate that, by reducing the time step in the coarse-resolution (<span class="inline-formula">∼100</span> km) OpenIFS model, one can alleviate some climate biases at a lower cost than by increasing the horizontal resolution.</p>https://gmd.copernicus.org/articles/17/1813/2024/gmd-17-1813-2024.pdf |
| spellingShingle | A. Savita J. Kjellsson J. Kjellsson R. Pilch Kedzierski R. Pilch Kedzierski M. Latif M. Latif T. Rahm T. Rahm S. Wahl W. Park W. Park Assessment of climate biases in OpenIFS version 43r3 across model horizontal resolutions and time steps Geoscientific Model Development |
| title | Assessment of climate biases in OpenIFS version 43r3 across model horizontal resolutions and time steps |
| title_full | Assessment of climate biases in OpenIFS version 43r3 across model horizontal resolutions and time steps |
| title_fullStr | Assessment of climate biases in OpenIFS version 43r3 across model horizontal resolutions and time steps |
| title_full_unstemmed | Assessment of climate biases in OpenIFS version 43r3 across model horizontal resolutions and time steps |
| title_short | Assessment of climate biases in OpenIFS version 43r3 across model horizontal resolutions and time steps |
| title_sort | assessment of climate biases in openifs version 43r3 across model horizontal resolutions and time steps |
| url | https://gmd.copernicus.org/articles/17/1813/2024/gmd-17-1813-2024.pdf |
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