Evaluation of vertically resolved longwave radiation in SPARTACUS-Urban 0.7.3 and the sensitivity to urban surface temperatures
<p>Cities' materials and urban form impact radiative exchanges and surface and air temperatures. Here, the SPARTACUS (Speedy Algorithm for Radiative Transfer through Cloud Sides) multi-layer approach to modelling longwave radiation in urban areas (SPARTACUS-Urban) is evaluated using the e...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2023-10-01
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| Series: | Geoscientific Model Development |
| Online Access: | https://gmd.copernicus.org/articles/16/5931/2023/gmd-16-5931-2023.pdf |
| _version_ | 1797654476574687232 |
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| author | M. A. Stretton W. Morrison W. Morrison R. J. Hogan R. J. Hogan S. Grimmond |
| author_facet | M. A. Stretton W. Morrison W. Morrison R. J. Hogan R. J. Hogan S. Grimmond |
| author_sort | M. A. Stretton |
| collection | DOAJ |
| description | <p>Cities' materials and urban form impact radiative exchanges and surface and air temperatures. Here, the SPARTACUS (Speedy Algorithm for Radiative Transfer through Cloud Sides) multi-layer approach to modelling longwave radiation in urban areas (SPARTACUS-Urban) is evaluated using the explicit DART (Discrete Anisotropic Radiative Transfer) model. SPARTACUS-Urban describes realistic 3D urban geometry statistically rather than assuming an infinite street canyon. Longwave flux profiles are compared across an August day for a 2 km <span class="inline-formula">×</span> 2 km domain in central London. Simulations are conducted with multiple temperature configurations, including realistic temperature profiles derived from thermal camera observations. The SPARTACUS-Urban model performs well (cf. DART, 2022) when all facets are prescribed a single temperature, with normalised bias errors (nBEs) <span class="inline-formula"><2.5</span> % for downwelling fluxes, and <span class="inline-formula"><0.5</span> % for top-of-canopy upwelling fluxes. Errors are larger (nBE <span class="inline-formula"><8</span> %) for net longwave fluxes from walls and roofs. Using more realistic surface temperatures, varying depending on surface shading, the nBE in upwelling longwave increases to <span class="inline-formula">∼2</span> %. Errors in roof and wall net longwave fluxes increase through the day, but nBEs are still 8 %–11 %. This increase in nBE occurs because SPARTACUS-Urban represents vertical but not horizontal surface temperature variation within a domain. Additionally, SPARTACUS-Urban outperforms the Harman single-layer canyon approach, particularly in the longwave interception by roofs. We conclude that SPARTACUS-Urban accurately predicts longwave fluxes, requiring less computational time (cf. DART, 2022) but with larger errors when surface temperatures vary due to shading. SPARTACUS-Urban could enhance multi-layer urban energy balance scheme prediction of within-canopy temperatures and fluxes.</p> |
| first_indexed | 2024-03-11T17:00:02Z |
| format | Article |
| id | doaj.art-19e7a2e855054a0399ee16e4455183ad |
| institution | Directory Open Access Journal |
| issn | 1991-959X 1991-9603 |
| language | English |
| last_indexed | 2024-03-11T17:00:02Z |
| publishDate | 2023-10-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Geoscientific Model Development |
| spelling | doaj.art-19e7a2e855054a0399ee16e4455183ad2023-10-20T10:24:24ZengCopernicus PublicationsGeoscientific Model Development1991-959X1991-96032023-10-01165931594710.5194/gmd-16-5931-2023Evaluation of vertically resolved longwave radiation in SPARTACUS-Urban 0.7.3 and the sensitivity to urban surface temperaturesM. A. Stretton0W. Morrison1W. Morrison2R. J. Hogan3R. J. Hogan4S. Grimmond5Department of Meteorology, University of Reading, Reading, UKDepartment of Meteorology, University of Reading, Reading, UKChair of Environmental Meteorology, Faculty of Environment and Natural Resources, University of Freiburg, Freiburg, GermanyDepartment of Meteorology, University of Reading, Reading, UKEuropean Centre for Medium-Range Weather Forecasts, Reading, UKDepartment of Meteorology, University of Reading, Reading, UK<p>Cities' materials and urban form impact radiative exchanges and surface and air temperatures. Here, the SPARTACUS (Speedy Algorithm for Radiative Transfer through Cloud Sides) multi-layer approach to modelling longwave radiation in urban areas (SPARTACUS-Urban) is evaluated using the explicit DART (Discrete Anisotropic Radiative Transfer) model. SPARTACUS-Urban describes realistic 3D urban geometry statistically rather than assuming an infinite street canyon. Longwave flux profiles are compared across an August day for a 2 km <span class="inline-formula">×</span> 2 km domain in central London. Simulations are conducted with multiple temperature configurations, including realistic temperature profiles derived from thermal camera observations. The SPARTACUS-Urban model performs well (cf. DART, 2022) when all facets are prescribed a single temperature, with normalised bias errors (nBEs) <span class="inline-formula"><2.5</span> % for downwelling fluxes, and <span class="inline-formula"><0.5</span> % for top-of-canopy upwelling fluxes. Errors are larger (nBE <span class="inline-formula"><8</span> %) for net longwave fluxes from walls and roofs. Using more realistic surface temperatures, varying depending on surface shading, the nBE in upwelling longwave increases to <span class="inline-formula">∼2</span> %. Errors in roof and wall net longwave fluxes increase through the day, but nBEs are still 8 %–11 %. This increase in nBE occurs because SPARTACUS-Urban represents vertical but not horizontal surface temperature variation within a domain. Additionally, SPARTACUS-Urban outperforms the Harman single-layer canyon approach, particularly in the longwave interception by roofs. We conclude that SPARTACUS-Urban accurately predicts longwave fluxes, requiring less computational time (cf. DART, 2022) but with larger errors when surface temperatures vary due to shading. SPARTACUS-Urban could enhance multi-layer urban energy balance scheme prediction of within-canopy temperatures and fluxes.</p>https://gmd.copernicus.org/articles/16/5931/2023/gmd-16-5931-2023.pdf |
| spellingShingle | M. A. Stretton W. Morrison W. Morrison R. J. Hogan R. J. Hogan S. Grimmond Evaluation of vertically resolved longwave radiation in SPARTACUS-Urban 0.7.3 and the sensitivity to urban surface temperatures Geoscientific Model Development |
| title | Evaluation of vertically resolved longwave radiation in SPARTACUS-Urban 0.7.3 and the sensitivity to urban surface temperatures |
| title_full | Evaluation of vertically resolved longwave radiation in SPARTACUS-Urban 0.7.3 and the sensitivity to urban surface temperatures |
| title_fullStr | Evaluation of vertically resolved longwave radiation in SPARTACUS-Urban 0.7.3 and the sensitivity to urban surface temperatures |
| title_full_unstemmed | Evaluation of vertically resolved longwave radiation in SPARTACUS-Urban 0.7.3 and the sensitivity to urban surface temperatures |
| title_short | Evaluation of vertically resolved longwave radiation in SPARTACUS-Urban 0.7.3 and the sensitivity to urban surface temperatures |
| title_sort | evaluation of vertically resolved longwave radiation in spartacus urban 0 7 3 and the sensitivity to urban surface temperatures |
| url | https://gmd.copernicus.org/articles/16/5931/2023/gmd-16-5931-2023.pdf |
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