Authors: Michel Y. Louge ORCID 0000-0002-1155-9163 myl3@cornell.edu Alexandre Valance ORCID 0000-0001-8076-2192 alexandre.valance@univ-rennes1.fr Jiannong Fang ORCID 0000-0002-9205-6444 jiannong.fang@epfl.ch Stephen J. Harnett sjh276@cornell.edu Fernando Porté-Agel ORCID 0000-0002-9913-3350 fernando.porte-agel@epfl.ch Patrick Chasle patrick.chasle@univ-rennes1.fr Document Created: November 18, 2023 === Abstract === This collection contains supporting information for M. Y. Louge, A. Valance, J. Fang, S. Harnett, F. Porte-Agel, P. Chasle, Evolution of turbulent boundary conditions on the surface of large barchan dunes: anomalies in aerodynamic roughness and shear velocity, aeolian thresholds and the role of dune skewness, J. Geophys. Res. Earth Surface (2023). In this work, we recorded aerodynamic roughness and shear velocity along transects on and around crescent-shaped barchan dunes of 4.5m and 27m height above the horizontal rock-covered Qatar desert by fitting to the log-law time-averaged vertical velocity profiles acquired from triads of ultrasonic anemometers penetrating the inner turbulent boundary layer. Shear velocity first decreased, then recovered as air climbed on the dune, with a local maximum ahead of the crest as predicted by the Jackson and Hunt (1975) theory. Unlike flows over gentler bedforms without a slope discontinuity, an anomalous peak of shear velocity also arose on the dune centerline at the brink, which the theory attributed to skewness in the dune transect profile. A correlation of wind speed with aeolian sand flux measured on dune revealed the existence of three hysteretic transport thresholds. Above the second one, shear velocity and aerodynamic roughness transitioned to a log-law passing through the Bagnold (1941) focal point. The dunes' rocky surroundings and topography produced an aerodynamic roughness at odds with the Nikuradse (1933) data for fully-developed turbulent boundary layers. Large-eddy numerical simulations illustrated the sensitivity of shear velocity to wide changes in aerodynamic roughness from desert floor to dune surface. === Reuse and Citation === This dataset is shared under a Creative Commons 1.0 Universal Public Domain Dedication (https://creativecommons.org/publicdomain/zero/1.0/). The material can be copied, modified and used without permission, but attribution to the original authors is always appreciated. Please cite this dataset as: Louge, Michel, Alexandre Valance, Jiannong Fang, Fernando Porté-Agel (2023) Data from: Evolution of turbulent boundary conditions on the surface of large barchan dunes: anomalies in aerodynamic roughness and shear velocity, aeolian thresholds and the role of dune skewness. [Dataset]. Cornell University Library eCommons Repository. https://doi.org/10.7298/6md9-1377 === Sponsorship === This collection was made possible by the support of NPRP grants 09-546-2-206 and 6-059-2-023 from the Qatar National Research Fund, and by a Qatar Foundation Research Excellence Award. It was supported in part by the National Science Foundation under Grant No. NSF PHY-1748958, which allowed MYL and AV to attend a program at the Kavli Institute for Theoretical Physics, and by the ISblue project, Interdisciplinary Graduate School for the Blue Planet (ANR-17-EURE-0015) that fostered related discussions on dune modeling. AV acknowledges the support of the French Research National Agency through project ANR-21-CE30-0066. === Subject === Desertification, Erosion, Turbulence, Modeling, Large eddy simulation, hyper-arid mobile dune, atmospheric boundary layer, anemometry === Contents of the collection === The collection contains one .xlsx Excel workbook (A), 6 .csv worksheets (B-G), and one archival bundle (H) as follows. == (A) Excel workbook LougeEtAl_JGR-ES_2023_SupportingInformation.xlsx == An Excel workbook of data and its reduction with the following 21 worksheets. Note that this Workbook contains formatting and figures that may not be preserved when opening outside of Excel. (1) topographyNadine Topography of Nadine dune of 4.5m height, tilted to a horizontal outline and with origin at the outline barycenter. (2) DaqNadine Data acquisition times of all roving stations on Nadine dune. (3) anemometryNadine Anemometry on all triads for Nadine dune, excluding long-term records at triads 1, 30, 47-49. (4) Fig2 Profiles and records in Fig. 2. (5) Fig3 Data for Fig. 3. (6) Fig4 Profiles and records in Fig. 4. (7) Fig5 Profiles and records in Fig. 5. (8) topographyChris Topography of Chris dune of 27m height, tilted to a horizontal outline and with origin at the outline barycenter. (9) DaqChris Data acquisition times of all roving stations on Chris dune. (10) anemometryChris Anemometry on Chris dune. (11) Fig6 Profiles and records in Fig. 6. (12) Figs7&8 Profiles and records in Figs. 7 and 8. (13) Fig9 Dune topography and longitudinal transect of u*/ur* in topographyNadine and Fig5 worksheets. (14) Fig10 Profiles and records in Fig. 10. (15) NikuradseData Reduction of data in Nikuradse, J. (1933). Strömungsgesetze in rauhen Rohren. Forschungsarbeiten aus dem Gebiete des Ingenieurwesens 361. VDI-Verlag, Berlin (in German). (16) GuoData Data from Guo, J., 2020. Empirical model for Shields diagram and its applications. Journal of Hydraulic Engineering, 146(6), p.04020038, https://doi.org/10.1061/(ASCE)HY.1943-7900.0001739. (17) PahtzData Shields stress threshold in atmospheric air, from Fig. 3 in Pähtz, T. and Durán, O., 2018. The cessation threshold of nonsuspended sediment transport across aeolian and fluvial environments. Journal of Geophysical Research: Earth Surface, 123(8), pp.1638-1666, https://doi.org/10.1029/2017JF004580 (18) AndreottiData Shields stress threshold data under reduced pressure from Andreotti, B., Claudin, P., Iversen, J.J., Merrison, J.P. and Rasmussen, K.R., 2021. A lower-than-expected saltation threshold at Martian pressure and below. Proceedings of the National Academy of Sciences, 118(5), p.e2012386118, https://doi.org/10.1073/pnas.2012386118 (19) SwannData Shields stress threshold under reduced pressure from Swann, C., Sherman, D. & Ewing, R. 2020 Experimentally-derived thresholds for windblown sand on Mars, Geophys. Res. Lett. 47, 490 e2019GL084484, https://doi.org/10.1029/2019GL084484 (20) Fig11 Transects of Fig. 11. (21) Fig13 LES simulations transects of Fig. 13. == (B) worksheet AnemometryRovingNadine.csv == Unfettered, exhaustive data set of speed and direction whence wind comes for the anemometer triad at all roving stations on the Nadine dune. == (C) worksheet AnemometryDuneNadine.csv == Unfettered, exhaustive data set of speed and direction whence wind comes for the anemometer triad at the fixed station on the Nadine dune, together with the simultaneous acoustic impact signal. == (D) worksheet AnemometryFloorNadine.csv == Unfettered, exhaustive data set of speed and direction whence wind comes for the anemometer triad at the fixed station on the desert floor upwind of the Nadine dune. == (E) worksheet AnemometryRovingChris.csv == Unfettered, exhaustive data set of speed and direction whence wind comes for the anemometer triad at all roving stations on the Chris dune. == (F) worksheet AnemometryDuneChris.csv == Unfettered, exhaustive data set of speed and direction whence wind comes for the anemometer triad at the fixed station on the Chris dune. == (G) worksheet AnemometryFloorChris.csv == Unfettered, exhaustive data set of speed and direction whence wind comes for the anemometer triad at the fixed station on the desert floor upwind of the Chris dune. == (H) LougeEtAL_SupportingInformation_ArchivalBundle.zip == Archival Bundle for LougeEtAl_JGR-ES_2023_SupportingInformation.xlsx, including .csv files of all worksheets in the workbook, plus extracted charts (as .png), figures (as .png), formulas (as .txt) and formatting (as .html) from all worksheets in the workbook.