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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...
Autores principales: | , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
John Wiley and Sons Inc.
2015
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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. |
format | Online Article Text |
id | pubmed-5020594 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2015 |
publisher | John Wiley and Sons Inc. |
record_format | MEDLINE/PubMed |
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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