Tornado-scale vortices in the tropical cyclone boundary layer: numerical simulation with the WRF–LES framework
<p>A tornado-scale vortex in the tropical cyclone (TC) boundary layer (TCBL) has been observed in intense hurricanes and the associated intense turbulence poses a severe threat to the manned research aircraft when it penetrates hurricane eyewalls at a lower altitude. In this study, a numerical...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-02-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/19/2477/2019/acp-19-2477-2019.pdf |
| _version_ | 1818218620367405056 |
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| author | L. Wu L. Wu Q. Liu Y. Li |
| author_facet | L. Wu L. Wu Q. Liu Y. Li |
| author_sort | L. Wu |
| collection | DOAJ |
| description | <p>A tornado-scale vortex in the tropical cyclone (TC) boundary layer (TCBL)
has been observed in intense hurricanes and the associated intense turbulence
poses a severe threat to the manned research aircraft when it penetrates
hurricane eyewalls at a lower altitude. In this study, a numerical experiment
in which a TC evolves in a large-scale background over the western North
Pacific is conducted using the Advanced Weather Research and Forecast (WRF)
model by incorporating the large-eddy simulation (LES) technique. The
simulated tornado-scale vortex shows features similar to those revealed with
limited observational data, including the updraft–downdraft couplet, the
sudden jump of wind speeds, the location along the inner edge of the eyewall,
and the small horizontal scale. It is suggested that the WRF–LES framework
can successfully simulate the tornado-scale vortex with grids at a
resolution of 37 m that cover the TC eye and eyewall.</p>
<p>The simulated tornado-scale vortex is a cyclonic circulation with a small
horizontal scale of <span class="inline-formula">∼1</span> km in the TCBL. It is accompanied by strong
updrafts (more than 15 m s<span class="inline-formula"><sup>−1</sup></span>) and large vertical components of
relative vorticity (larger than 0.2 s<span class="inline-formula"><sup>−1</sup></span>). The tornado-scale vortex
favorably occurs at the inner edge of the enhanced eyewall convection or
rainband within the saturated, high-<span class="inline-formula"><i>θ</i><sub>e</sub></span> layer, mostly below
an altitude of 2 km. In nearly all the simulated tornado-scale vortices,
the narrow intense updraft is coupled with the relatively broad downdraft,
constituting one or two updraft–downdraft couplets, as observed by the
research aircraft. The presence of the tornado-scale vortex also leads to
significant gradients in the near-surface wind speed and wind gusts.</p> |
| first_indexed | 2024-12-12T07:26:39Z |
| format | Article |
| id | doaj.art-15046208508d48d5b10ba9355de41b4e |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-12T07:26:39Z |
| publishDate | 2019-02-01 |
| publisher | Copernicus Publications |
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| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-15046208508d48d5b10ba9355de41b4e2022-12-22T00:33:07ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242019-02-01192477248710.5194/acp-19-2477-2019Tornado-scale vortices in the tropical cyclone boundary layer: numerical simulation with the WRF–LES frameworkL. Wu0L. Wu1Q. Liu2Y. Li3Pacific Typhoon Research Center and Key Laboratory of Meteorological Disaster of Ministry of Education, Nanjing University of Information Science and Technology, Nanjing, ChinaDepartment of Atmospheric and Oceanic Sciences and Institute of Atmospheric Sciences, Fudan University, Shanghai, ChinaPacific Typhoon Research Center and Key Laboratory of Meteorological Disaster of Ministry of Education, Nanjing University of Information Science and Technology, Nanjing, ChinaPacific Typhoon Research Center and Key Laboratory of Meteorological Disaster of Ministry of Education, Nanjing University of Information Science and Technology, Nanjing, China<p>A tornado-scale vortex in the tropical cyclone (TC) boundary layer (TCBL) has been observed in intense hurricanes and the associated intense turbulence poses a severe threat to the manned research aircraft when it penetrates hurricane eyewalls at a lower altitude. In this study, a numerical experiment in which a TC evolves in a large-scale background over the western North Pacific is conducted using the Advanced Weather Research and Forecast (WRF) model by incorporating the large-eddy simulation (LES) technique. The simulated tornado-scale vortex shows features similar to those revealed with limited observational data, including the updraft–downdraft couplet, the sudden jump of wind speeds, the location along the inner edge of the eyewall, and the small horizontal scale. It is suggested that the WRF–LES framework can successfully simulate the tornado-scale vortex with grids at a resolution of 37 m that cover the TC eye and eyewall.</p> <p>The simulated tornado-scale vortex is a cyclonic circulation with a small horizontal scale of <span class="inline-formula">∼1</span> km in the TCBL. It is accompanied by strong updrafts (more than 15 m s<span class="inline-formula"><sup>−1</sup></span>) and large vertical components of relative vorticity (larger than 0.2 s<span class="inline-formula"><sup>−1</sup></span>). The tornado-scale vortex favorably occurs at the inner edge of the enhanced eyewall convection or rainband within the saturated, high-<span class="inline-formula"><i>θ</i><sub>e</sub></span> layer, mostly below an altitude of 2 km. In nearly all the simulated tornado-scale vortices, the narrow intense updraft is coupled with the relatively broad downdraft, constituting one or two updraft–downdraft couplets, as observed by the research aircraft. The presence of the tornado-scale vortex also leads to significant gradients in the near-surface wind speed and wind gusts.</p>https://www.atmos-chem-phys.net/19/2477/2019/acp-19-2477-2019.pdf |
| spellingShingle | L. Wu L. Wu Q. Liu Y. Li Tornado-scale vortices in the tropical cyclone boundary layer: numerical simulation with the WRF–LES framework Atmospheric Chemistry and Physics |
| title | Tornado-scale vortices in the tropical cyclone boundary layer: numerical simulation with the WRF–LES framework |
| title_full | Tornado-scale vortices in the tropical cyclone boundary layer: numerical simulation with the WRF–LES framework |
| title_fullStr | Tornado-scale vortices in the tropical cyclone boundary layer: numerical simulation with the WRF–LES framework |
| title_full_unstemmed | Tornado-scale vortices in the tropical cyclone boundary layer: numerical simulation with the WRF–LES framework |
| title_short | Tornado-scale vortices in the tropical cyclone boundary layer: numerical simulation with the WRF–LES framework |
| title_sort | tornado scale vortices in the tropical cyclone boundary layer numerical simulation with the wrf les framework |
| url | https://www.atmos-chem-phys.net/19/2477/2019/acp-19-2477-2019.pdf |
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