Fiedler, S, Schepanski, K, Heinold, B et al. (2 more authors) (2013) Climatology of nocturnal low-level jets over North Africa and implications for modeling mineral dust emission. Journal of Geophysical Research D: Atmospheres, 118 (12). 6100 - 6121. ISSN 0148-0227
Abstract
This study presents the first climatology for the dust emission amount associated with Nocturnal Low-Level Jets (NLLJs) in North Africa. These wind speed maxima near the top of the nocturnal boundary layer can generate near-surface peak winds due to shear-driven turbulence in the course of the night and the NLLJ breakdown during the following morning. The associated increase in the near-surface wind speed is a driver for mineral dust emission. A new detection algorithm for NLLJs is presented and used for a statistical assessment of NLLJs in 32 years of ERA-Interim reanalysis from the European Centre for Medium-Range Weather Forecasts. NLLJs occur in 29% of the nights in the annual and spatial mean. The NLLJ climatology shows a distinct annual cycle with marked regional differences. Maxima of up to 80% NLLJ frequency are found where low-level baroclinicity and orographic channels cause favorable conditions, e.g., over the Bodélé Depression, Chad, for November-February and along the West Saharan and Mauritanian coast for April-September. Downward mixing of NLLJ momentum to the surface causes 15% of mineral dust emission in the annual and spatial mean and can be associated with up to 60% of the total dust amount in specific areas, e.g., the Bodélé Depression and south of the Hoggar-Tibesti Channel. The sharp diurnal cycle underlines the importance of using wind speed information with high temporal resolution as driving fields for dust emission models. Key Points Long-term climatology of Nocturnal Low-Level Jets (NLLJ) over North Africa Newly developed automated detection algorithm for NLLJs NLLJs contribute 15 % to North African dust emission in annual and spatial mean.
Metadata
Item Type: | Article |
---|---|
Authors/Creators: |
|
Copyright, Publisher and Additional Information: | An edited version of this paper was published by AGU. Copyright (2013) American Geophysical Union. Fiedler, S, Schepanski, K, Heinold, B, Knippertz, P and Tegen, I (2013) Climatology of nocturnal low-level jets over North Africa and implications for modeling mineral dust emission. Journal of Geophysical Research D: Atmospheres, 118 (12). To view the published open abstract, go to http://dx.doi.org/10.1002/jgrd.50394 |
Keywords: | Diurnal cycle; Dust emission; ERA-Interim reanalysis; Harmattan; Nocturnal low-level jet; Saharan heat low |
Dates: |
|
Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 10 Oct 2013 11:53 |
Last Modified: | 15 Sep 2014 02:57 |
Published Version: | http://dx.doi.org/10.1002/jgrd.50394 |
Status: | Published |
Publisher: | American Geophysical Union |
Identification Number: | 10.1002/jgrd.50394 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:76582 |