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The importance of rare, high‐wind events for dust uplift in northern Africa

Dust uplift is a nonlinear thresholded function of wind speed and therefore particularly sensitive to the long tails of observed wind speed probability density functions. This suggests that a few rare high‐wind events can contribute substantially to annual dust emission. Here we quantify the relativ...

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Autores principales: Cowie, Sophie M., Marsham, John H., Knippertz, Peter
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2015
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5020594/
https://www.ncbi.nlm.nih.gov/pubmed/27667872
http://dx.doi.org/10.1002/2015GL065819
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author Cowie, Sophie M.
Marsham, John H.
Knippertz, Peter
author_facet Cowie, Sophie M.
Marsham, John H.
Knippertz, Peter
author_sort Cowie, Sophie M.
collection PubMed
description Dust uplift is a nonlinear thresholded function of wind speed and therefore particularly sensitive to the long tails of observed wind speed probability density functions. This suggests that a few rare high‐wind events can contribute substantially to annual dust emission. Here we quantify the relative roles of different wind speeds to dust‐generating winds using surface synoptic observations of dust emission and wind from northern Africa. The results show that winds between 2 and 5 m s(−1) above the threshold cause the most emission. Of the dust‐generating winds, 25% is produced by very rare events occurring only at 0.1 to 1.4% of the time, depending on the region. Dust‐producing winds are underestimated in ERA‐I, since it misses the long tail found in observations. ERA‐I overpredicts (underpredicts) the frequency of emission strength winds in the southern (northern) regions. These problems cannot be solved by simple tunings. Finally, we show that rare events make the largest contribution to interannual variability in dust‐generating winds and that ERA severely underestimates this interannual variability.
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spelling pubmed-50205942016-09-23 The importance of rare, high‐wind events for dust uplift in northern Africa Cowie, Sophie M. Marsham, John H. Knippertz, Peter Geophys Res Lett Research Letters Dust uplift is a nonlinear thresholded function of wind speed and therefore particularly sensitive to the long tails of observed wind speed probability density functions. This suggests that a few rare high‐wind events can contribute substantially to annual dust emission. Here we quantify the relative roles of different wind speeds to dust‐generating winds using surface synoptic observations of dust emission and wind from northern Africa. The results show that winds between 2 and 5 m s(−1) above the threshold cause the most emission. Of the dust‐generating winds, 25% is produced by very rare events occurring only at 0.1 to 1.4% of the time, depending on the region. Dust‐producing winds are underestimated in ERA‐I, since it misses the long tail found in observations. ERA‐I overpredicts (underpredicts) the frequency of emission strength winds in the southern (northern) regions. These problems cannot be solved by simple tunings. Finally, we show that rare events make the largest contribution to interannual variability in dust‐generating winds and that ERA severely underestimates this interannual variability. John Wiley and Sons Inc. 2015-10-16 2015-10-08 /pmc/articles/PMC5020594/ /pubmed/27667872 http://dx.doi.org/10.1002/2015GL065819 Text en ©2015. The Authors. This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial‐NoDerivs (http://creativecommons.org/licenses/by-nc-nd/4.0/) License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.
spellingShingle Research Letters
Cowie, Sophie M.
Marsham, John H.
Knippertz, Peter
The importance of rare, high‐wind events for dust uplift in northern Africa
title The importance of rare, high‐wind events for dust uplift in northern Africa
title_full The importance of rare, high‐wind events for dust uplift in northern Africa
title_fullStr The importance of rare, high‐wind events for dust uplift in northern Africa
title_full_unstemmed The importance of rare, high‐wind events for dust uplift in northern Africa
title_short The importance of rare, high‐wind events for dust uplift in northern Africa
title_sort importance of rare, high‐wind events for dust uplift in northern africa
topic Research Letters
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5020594/
https://www.ncbi.nlm.nih.gov/pubmed/27667872
http://dx.doi.org/10.1002/2015GL065819
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