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Universiteit Utrecht (2013)

Quantification of soil erosion by dust devil in the Jordan Badia

Broersen, T.

Titre  : Quantification of soil erosion by dust devil in the Jordan Badia

Auteur : Broersen, T.

Université de soutenance : Universiteit Utrecht

Grade : Master Thesis 2013

Résumé
This study aims to provide a quantitative estimate of the amount of erosion caused by dust devils in the Jordan Badia, and to find the meteorological variables that drive the formation of these dust devils. To achieve this goal a field study was done in Al-Majidyya, Jordan, on 9 days in the period of July 23rd – August 5th, 2012, during which a total of 518 dust devils were observed. Dust devils were observed between 09:09 and 17:34, were most active between 12:00 and 13:00, and were significantly more active during the first than during the second part of day. Temperature lapse rates of at least 0.76 °C/m were required for dust devil formation, and dust devils became more frequent with temperature lapse rates increasing up to a value of 1.2 °C/m. Dust devil frequency remained constant with further increases in temperature lapse rate. Dust devils were observed in the wind speed range of 0.1 – 7.5 m/s, and showed a positive relation with wind speed up to a value of 2 m/s. For values of the wind speed higher than 3 m/s, the relation became negative. A cyclic pattern was observed in the lower 2.5 m of the atmosphere during which temperature lapse rate and wind speed were highly correlated and showed a cyclic pattern of rising and falling values. This cyclic pattern was proposed to negatively influence dust devil frequency. Annual amounts of erosion for the Jordan Badia were estimated at 9.79 kg/ha of locally and 0.03 kg/ha of regionally lost soil. These values were found to be low compared to other dust devil studies and other dust events. Compared to normal wind erosion, dust devils were found to be of low importance in this area. However, dust devils do contribute to atmospheric dust loading, which affects the atmospheric radiation balance, may pose health issues to humans and livestock, and may cause a loss of primary nutrients from the area. This study provides the only estimation of erosion by dust devils available for the Jordan Badia

Mots clés : Geowetenschappen ; dust devils, dust devil, Jordan Badia, convective vortex, convective vortices, temperature gradient, temperature lapse rate, wind erosion

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Page publiée le 14 mars 2015, mise à jour le 28 septembre 2017