Seasonal Variations in Airflow Over the Namib Dune, Gale Crater, Mars: Implications for Dune Dynamics
Seasonal Variations in Airflow Over the Namib Dune, Gale Crater, Mars: Implications for Dune Dynamics
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DOI：
10.1029/2018gl079598
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发表时间：
2018-09-28
影响因子：
5.2
通讯作者：
Cooper, J. Andrew G.
中科院分区：
文献类型：
--
作者：
Cornwall, Carin;Jackson, Derek W. T.;Cooper, J. Andrew G.
沙丘长度尺度气流模拟提供了关于风沙床状响应和复杂的近地表三维风型的新见解，这是以前中尺度模式所不能解决的。在1米的地表分辨率下，好奇号的风数据被用来调查火星纳米布沙丘的风沙环境，改善了对粒流、粒流活动和涟漪迁移的季节性限制。根据卫星图像、气流模式和地表切变应力，风沙活动增强，滑面推进发生在早春。秋风和冬风也有利于风沙活动，但在与风数据重叠的卫星图像中检测到了微小的移动。在夏季，纳米布沙丘上巨大的石屑涟漪的迁移可能会增加滑面上的泥沙沉积。这些结果有助于更好地理解纳米布沙丘的整体迁移模式，这可以外推到巴格诺德沙丘地区的其他沙丘上。简单来说，在1米分辨率下，小尺度气流模拟可以为火星上的沉积物迁移和沙丘迁移提供新的见解。结合好奇号月球车收集的风数据，这项研究为火星沉积物的移动提供了改进的、现实的约束，并说明了涟漪是如何根据风速和风向的变化季节性形成和迁移的。根据模拟结果和卫星监测，春季北风对沙丘迁移的影响最大，但夏季和秋季较为安静，东南风继续促进波纹迁移，这可能有助于保持沙丘迁移的较慢速度，尽管风向相反。根据模拟结果，冬季北风强度大，应该会产生与春季相似的迁移率，但根据卫星监测，沙丘迁徙停止。沙丘表面沙粒之间的少量霜冻可能是沙丘迁移停止的原因。这些结果也适用于巴格诺德沙丘地区的其他沙丘，这些沙丘很可能经历了相同的泥沙运移季节模式。
Dune length scale airflow modeling provides new insights on eolian bedform response and complex near-surface 3-D wind patterns not previously resolved by mesoscale models. At a 1-m surface resolution, Curiosity wind data are used to investigate the eolian environment of the Namib dune on Mars, providing improved seasonal constraints on grainfall, grainflow activity, and ripple migration. Based on satellite images, airflow patterns, and surface shear stress, enhanced eolian activity, and slipface advancement occurs during early springtime. Autumn and winter winds are also favorable to eolian activity, but minimal movement was detected in satellite images overlapping with wind data. During the summer, the migration of large stoss ripples on the Namib dune may augment sediment deposition on the slipface. These results provide a better understanding of the overall migration pattern of the Namib dune, which can be extrapolated to other dunes in the Bagnold Dune Field.Plain Language Summary At 1-m resolution, small-scale airflow modeling can provide new insights into sediment transport and dune migration on Mars. Coupled with wind data collected by the Curiosity rover, this study provides improved, realistic constraints on Martian sediment movement and illustrates how ripples seasonally form and migrate according to changing wind speeds and directions. The spring season with northerly winds is the most influential for dune migration based on modeling results and satellite monitoring, but the quieter summer and autumn seasons with southeasterly winds continue to facilitate ripple migration, which may help maintain slower rates of dune migration despite the opposing wind direction. Based on modeling results, the winter season with high-magnitude northerly winds should produce migration rates similar to spring, but according to satellite monitoring, dune migration stops. Small amounts of frost in between sand grains on the dune surface may be responsible for this halt in dune migration. These results can be applied to other dunes in the Bagnold Dune Field, which likely experience the same seasonal patterns in sediment transport.