Valley floor inclination affecting valley winds and transport of passive tracers in idealised simulations
<p>In mountainous regions, diurnal thermally driven winds impact daily weather and air quality. This study investigates how the inclination of idealised valleys affects these winds and the transport of passive tracers using high-resolution numerical simulations with the Weather Research and Fo...
Saved in:
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-01-01
|
| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/25/511/2025/acp-25-511-2025.pdf |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1850096241150525440 |
|---|---|
| author | J. Mikkola A. Gohm V. A. Sinclair F. Bianchi |
| author_facet | J. Mikkola A. Gohm V. A. Sinclair F. Bianchi |
| author_sort | J. Mikkola |
| collection | DOAJ |
| description | <p>In mountainous regions, diurnal thermally driven winds impact daily weather and air quality. This study investigates how the inclination of idealised valleys affects these winds and the transport of passive tracers using high-resolution numerical simulations with the Weather Research and Forecasting (WRF) model. We explore a range of valley inclinations from 0 to 2.28°, bridging the gap between previous studies on flat and moderately inclined (up to 0.86°) idealised valleys and steeper (2–5°) real Himalayan valleys. We find that during daytime in the inclined valleys, up-valley winds penetrate deeper into the valleys and become stronger, up to a critical inclination beyond which the winds weaken. The flat-floored valley exhibits the strongest night-time down-valley winds overall, but surface-based down-valley winds are more prominent in inclined valleys. Steeper valleys enhance the vertical transport of passive tracers, resulting in ventilation at higher altitudes compared to the flat-floored valley. Despite stronger overall tracer outflow in the flat-floored valley, this occurs at lower altitudes, leading to most of the ventilated tracers being accumulated in the lowest few kilometres of the atmosphere. Consequently, steeper valleys are more efficient at ventilating tracers to the upper troposphere, which would, for example, lead to higher potential for long-range transport. These findings underscore the critical role of valley geometry in shaping wind patterns and pollutant transport, providing valuable insights for improving transport modelling in mountainous regions.</p> |
| format | Article |
| id | doaj-art-28eb62da50c1409fb80808f71247b52d |
| institution | DOAJ |
| issn | 1680-7316 1680-7324 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj-art-28eb62da50c1409fb80808f71247b52d2025-08-20T02:41:16ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242025-01-012551153310.5194/acp-25-511-2025Valley floor inclination affecting valley winds and transport of passive tracers in idealised simulationsJ. Mikkola0A. Gohm1V. A. Sinclair2F. Bianchi3Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, Helsinki, FinlandDepartment of Atmospheric and Cryospheric Sciences, University of Innsbruck, Innsbruck, AustriaInstitute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, Helsinki, FinlandInstitute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, Helsinki, Finland<p>In mountainous regions, diurnal thermally driven winds impact daily weather and air quality. This study investigates how the inclination of idealised valleys affects these winds and the transport of passive tracers using high-resolution numerical simulations with the Weather Research and Forecasting (WRF) model. We explore a range of valley inclinations from 0 to 2.28°, bridging the gap between previous studies on flat and moderately inclined (up to 0.86°) idealised valleys and steeper (2–5°) real Himalayan valleys. We find that during daytime in the inclined valleys, up-valley winds penetrate deeper into the valleys and become stronger, up to a critical inclination beyond which the winds weaken. The flat-floored valley exhibits the strongest night-time down-valley winds overall, but surface-based down-valley winds are more prominent in inclined valleys. Steeper valleys enhance the vertical transport of passive tracers, resulting in ventilation at higher altitudes compared to the flat-floored valley. Despite stronger overall tracer outflow in the flat-floored valley, this occurs at lower altitudes, leading to most of the ventilated tracers being accumulated in the lowest few kilometres of the atmosphere. Consequently, steeper valleys are more efficient at ventilating tracers to the upper troposphere, which would, for example, lead to higher potential for long-range transport. These findings underscore the critical role of valley geometry in shaping wind patterns and pollutant transport, providing valuable insights for improving transport modelling in mountainous regions.</p>https://acp.copernicus.org/articles/25/511/2025/acp-25-511-2025.pdf |
| spellingShingle | J. Mikkola A. Gohm V. A. Sinclair F. Bianchi Valley floor inclination affecting valley winds and transport of passive tracers in idealised simulations Atmospheric Chemistry and Physics |
| title | Valley floor inclination affecting valley winds and transport of passive tracers in idealised simulations |
| title_full | Valley floor inclination affecting valley winds and transport of passive tracers in idealised simulations |
| title_fullStr | Valley floor inclination affecting valley winds and transport of passive tracers in idealised simulations |
| title_full_unstemmed | Valley floor inclination affecting valley winds and transport of passive tracers in idealised simulations |
| title_short | Valley floor inclination affecting valley winds and transport of passive tracers in idealised simulations |
| title_sort | valley floor inclination affecting valley winds and transport of passive tracers in idealised simulations |
| url | https://acp.copernicus.org/articles/25/511/2025/acp-25-511-2025.pdf |
| work_keys_str_mv | AT jmikkola valleyfloorinclinationaffectingvalleywindsandtransportofpassivetracersinidealisedsimulations AT agohm valleyfloorinclinationaffectingvalleywindsandtransportofpassivetracersinidealisedsimulations AT vasinclair valleyfloorinclinationaffectingvalleywindsandtransportofpassivetracersinidealisedsimulations AT fbianchi valleyfloorinclinationaffectingvalleywindsandtransportofpassivetracersinidealisedsimulations |