Título:
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The pulsating nature of large-scale Saharan dust transport as a result of interplays between mid-latitude Rossby waves and the North African Dipole Intensity
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Autor/a:
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Cuevas, E.; Gómez-Peláez, A.J.; Rodríguez, S.; Terradellas, E.; Basart, S.; García, R.D.; García, O.E.; Alonso-Pérez, S.
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Otros autores:
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Barcelona Supercomputing Center |
Abstract:
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It was previously shown that during August the export of Saharan dust to the Atlantic was strongly affected by the difference of the 700-hPa geopotential height anomaly between the subtropics and the tropics over North Africa, which was termed the North African Dipole Intensity (NAFDI). In this work a more comprehensive analysis of the NAFDI is performed, focusing on the entire summer dust season (June–September), and examining the interactions between the mid-latitude Rossby waves (MLRWs) and NAFDI. Widespread and notable aerosol optical depth (AOD) monthly anomalies are found for each NAFDI-phase over the dust corridors off the Sahara, indicating that NAFDI presents intra-seasonal variability and drives dust transport over both the Mediterranean basin and the North Atlantic. Those summer months with the same NAFDI-phase show similar AOD-anomaly patterns. Variations in NAFDI-phase also control the displacement of the Saharan Heat Low (SHL) westwards or eastwards through horizontal advection of temperature over Morocco-Western Sahara or eastern Algeria-Western Libya, respectively. The connection between the SHL and the NAFDI is quantified statistically by introducing two new daily indexes that account for their respective phases (NAFDI daily index -NAFDIDI-, and SHL longitudinal shift index -SHLLSI-) and explained physically using the energy equation of the atmospheric dynamics. The Pearson's correlation coefficient between the one–day-lag SHLLSI and the NAFDIDI for an extended summer season (1980–2013) is 0.78. A positive NAFDI is associated with the West-phase of the SHL, dust sources intensification on central Algeria, and positive AOD anomalies over this region and the Subtropical North Atlantic. A negative NAFDI is associated with the East-phase of the SHL, and positive AOD anomalies over central-eastern Sahara and the central-western Mediterranean Sea. The results point out that the phase changes of NAFDI at intra-seasonal time scale are conducted by those MLRWs that penetrate deeply into the low troposphere. |
Abstract:
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This work is part of the research activities developed by the WMO SDS-WAS Regional Centre for Northern Africa, Middle East
and Europe, held by AEMET and BSC-CNS. This study also contributes to Copernicus Atmosphere Monitoring Service (CAMS). Our
acknowledgment to ECMWF for providing MACC-dust reanalysis.
The authors wish to thank NCEP/NCAR Reanalysis Project. We acknowledge NASA LADS for providing MODIS data. The University of Granada (Spain) and its “Physics and Space Sciences” PhD Programme
are acknowledged by A. J. Gómez-Peláez and E. Cuevas. AEROATLAN project (CGL2015-17 66229-P), co-funded by the Ministry of Economy and Competitiveness of Spain and the European Regional Development Fund contributed to this study.
Sara Basart acknowledges the CICYT project (CGL2013-46736). |
Abstract:
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Peer Reviewed |
Materia(s):
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-Àrees temàtiques de la UPC::Energies -Dust--adverse effects -Sahara--Climate -Saharan dust -North African Dipole Intensity (NAFDI) -Saharan Heat Low (SHL) -Deserts--Àfrica del Nord -Sàhara |
Derechos:
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Attribution-NonCommercial-NoDerivs 4.0 Spain
http://creativecommons.org/licenses/by-nc-nd/4.0/es/ |
Tipo de documento:
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Artículo - Versión presentada Artículo |
Editor:
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Elsevier
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