Scaling of dust flux with friction velocity: time resolution effects
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en
Article de revue
Ce document a été publié dans
Journal of Geophysical Research: Atmospheres. 2020, vol. 125, n° 1, p. 1-16
American Geophysical Union
Résumé en anglais
The intermittency of aeolian soil erosion has motivated studies to extend to small time resolution (less than 15–30 min) the scaling property of erosion fluxes with the friction velocity urn:x-wiley:jgrd:media:jgrd55952: ...Lire la suite >
The intermittency of aeolian soil erosion has motivated studies to extend to small time resolution (less than 15–30 min) the scaling property of erosion fluxes with the friction velocity urn:x-wiley:jgrd:media:jgrd55952:jgrd55952-math-0001. However, common methods used to estimate urn:x-wiley:jgrd:media:jgrd55952:jgrd55952-math-0002 such as the law of the wall or the eddy covariance are only valid for stationary conditions, that is, long periods of 15–30 min. Unlike these methods, the wavelet transform method is applicable for nonstationary conditions. Here, this method is used to investigate the scaling property of the dust flux urn:x-wiley:jgrd:media:jgrd55952:jgrd55952-math-0003 with urn:x-wiley:jgrd:media:jgrd55952:jgrd55952-math-0004 at 1‐min and 10‐s resolutions, during erosion events. At 15‐min resolution, urn:x-wiley:jgrd:media:jgrd55952:jgrd55952-math-0005 and urn:x-wiley:jgrd:media:jgrd55952:jgrd55952-math-0006 estimated from the wavelet transform are identical to those obtained by eddy covariance. At smaller resolution, urn:x-wiley:jgrd:media:jgrd55952:jgrd55952-math-0007 and urn:x-wiley:jgrd:media:jgrd55952:jgrd55952-math-0008 exhibit strong fluctuations around their 15‐min trend, reflecting the nonstationarity of the flow and the intermittency of dust emission, respectively. While the 15‐min resolution urn:x-wiley:jgrd:media:jgrd55952:jgrd55952-math-0009 appears as correlated with urn:x-wiley:jgrd:media:jgrd55952:jgrd55952-math-0010 as with the mean wind speed urn:x-wiley:jgrd:media:jgrd55952:jgrd55952-math-0011, with decreasing resolution, urn:x-wiley:jgrd:media:jgrd55952:jgrd55952-math-0012 becomes less correlated with urn:x-wiley:jgrd:media:jgrd55952:jgrd55952-math-0013 but still significantly correlated with urn:x-wiley:jgrd:media:jgrd55952:jgrd55952-math-0014. Our results suggest that urn:x-wiley:jgrd:media:jgrd55952:jgrd55952-math-0015 is a suitable scaling parameter of urn:x-wiley:jgrd:media:jgrd55952:jgrd55952-math-0016 over usual 15‐ to 30‐min periods with the advantage of being height independent compared to urn:x-wiley:jgrd:media:jgrd55952:jgrd55952-math-0017. However, at small time resolution, urn:x-wiley:jgrd:media:jgrd55952:jgrd55952-math-0018 becomes more relevant to scale urn:x-wiley:jgrd:media:jgrd55952:jgrd55952-math-0019, the surface friction velocity becoming hardly accessible due to the absence of a constant momentum flux layer. Our study demonstrates the suitability of the wavelet transform to estimate dust fluxes at small time resolution or during nonstationary events.< Réduire
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