Aerodynamic roughness of rippled beds under active saltation at Earth-to-Mars atmospheric pressures
Abstract As winds blow over sand, grains are mobilized and reorganized into bedforms such as ripples and dunes. In turn, sand transport and bedforms affect the winds themselves. These complex interactions between winds and sediment render modeling of windswept landscapes challenging. A critical para...
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Nature Portfolio
2025-06-01
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| Series: | Nature Communications |
| Online Access: | https://doi.org/10.1038/s41467-025-60212-7 |
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| author | Carlos A. Alvarez Mathieu G. A. Lapôtre Christy Swann Ryan C. Ewing Pan Jia Philippe Claudin |
| author_facet | Carlos A. Alvarez Mathieu G. A. Lapôtre Christy Swann Ryan C. Ewing Pan Jia Philippe Claudin |
| author_sort | Carlos A. Alvarez |
| collection | DOAJ |
| description | Abstract As winds blow over sand, grains are mobilized and reorganized into bedforms such as ripples and dunes. In turn, sand transport and bedforms affect the winds themselves. These complex interactions between winds and sediment render modeling of windswept landscapes challenging. A critical parameter in such models is the aerodynamic roughness length, z 0, defined as the height above the bed at which wind velocity predicted from the log law drops to zero. In aeolian environments, z 0 can variably be controlled by the laminar viscous sublayer, grain roughness, form drag from bedforms, or the saltation layer. Estimates of z 0 are used on Mars, notably, to predict wind speeds, sand fluxes, and global circulation patterns; yet, no robust measurements of z 0 have been performed over rippled sand on Mars to date. Here, we measure z 0 over equilibrated rippled sand beds with active saltation under atmospheric pressures intermediate between those of Earth and Mars. Extrapolated to Mars, our results suggest that z 0 over rippled beds and under active saltation may be dominated by form drag across a plausible range of wind velocities, reaching values up to 1 cm—two orders of magnitude larger than typically assumed for flat beds under similar sediment transport conditions. |
| format | Article |
| id | doaj-art-2214a9834fca4550b60b36b504d04906 |
| institution | OA Journals |
| issn | 2041-1723 |
| language | English |
| publishDate | 2025-06-01 |
| publisher | Nature Portfolio |
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| series | Nature Communications |
| spelling | doaj-art-2214a9834fca4550b60b36b504d049062025-08-20T02:30:42ZengNature PortfolioNature Communications2041-17232025-06-011611910.1038/s41467-025-60212-7Aerodynamic roughness of rippled beds under active saltation at Earth-to-Mars atmospheric pressuresCarlos A. Alvarez0Mathieu G. A. Lapôtre1Christy Swann2Ryan C. Ewing3Pan Jia4Philippe Claudin5Department of Earth & Planetary Sciences, Stanford UniversityDepartment of Earth & Planetary Sciences, Stanford UniversityRCOASTAstromaterials & Exploration Science Division, NASA Johnson Space CenterSchool of Science, Harbin Institute of TechnologyPhysique et Mécanique des Milieux Hétérogènes, UMR 7636 CNRS—ESPCI Paris—Université PSL—Université Paris Cité—Sorbonne UniversitéAbstract As winds blow over sand, grains are mobilized and reorganized into bedforms such as ripples and dunes. In turn, sand transport and bedforms affect the winds themselves. These complex interactions between winds and sediment render modeling of windswept landscapes challenging. A critical parameter in such models is the aerodynamic roughness length, z 0, defined as the height above the bed at which wind velocity predicted from the log law drops to zero. In aeolian environments, z 0 can variably be controlled by the laminar viscous sublayer, grain roughness, form drag from bedforms, or the saltation layer. Estimates of z 0 are used on Mars, notably, to predict wind speeds, sand fluxes, and global circulation patterns; yet, no robust measurements of z 0 have been performed over rippled sand on Mars to date. Here, we measure z 0 over equilibrated rippled sand beds with active saltation under atmospheric pressures intermediate between those of Earth and Mars. Extrapolated to Mars, our results suggest that z 0 over rippled beds and under active saltation may be dominated by form drag across a plausible range of wind velocities, reaching values up to 1 cm—two orders of magnitude larger than typically assumed for flat beds under similar sediment transport conditions.https://doi.org/10.1038/s41467-025-60212-7 |
| spellingShingle | Carlos A. Alvarez Mathieu G. A. Lapôtre Christy Swann Ryan C. Ewing Pan Jia Philippe Claudin Aerodynamic roughness of rippled beds under active saltation at Earth-to-Mars atmospheric pressures Nature Communications |
| title | Aerodynamic roughness of rippled beds under active saltation at Earth-to-Mars atmospheric pressures |
| title_full | Aerodynamic roughness of rippled beds under active saltation at Earth-to-Mars atmospheric pressures |
| title_fullStr | Aerodynamic roughness of rippled beds under active saltation at Earth-to-Mars atmospheric pressures |
| title_full_unstemmed | Aerodynamic roughness of rippled beds under active saltation at Earth-to-Mars atmospheric pressures |
| title_short | Aerodynamic roughness of rippled beds under active saltation at Earth-to-Mars atmospheric pressures |
| title_sort | aerodynamic roughness of rippled beds under active saltation at earth to mars atmospheric pressures |
| url | https://doi.org/10.1038/s41467-025-60212-7 |
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