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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
Título : 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
Autor : Cuevas Agulló, Emilio ORCID RESEARCHERID SCOPUSID Gómez Peláez, Ángel Jesús ORCID RESEARCHERID SCOPUSID Rodríguez González, Sergio ORCID RESEARCHERID Terradellas, EnricBasart, SaraGarcía Cabrera, Rosa Delia ORCID RESEARCHERID García Rodríguez, Omaira Elena ORCID RESEARCHERID Alonso-Pérez, Silvia
Palabras clave : NAFDI; Rossby waves; SHL; Sahara; Dust; MODIS AOD; Atmospheric dynamics
Fecha de publicación : 2017
Editor: Elsevier
Citación : Atmospheric Environment. 2017, 167, p. 586–602
Versión del editor: https://doi.org/10.1016/j.atmosenv.2017.08.059
Resumen : 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 (JuneeSeptember), 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 NAFDIphase 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 oneeday-lag SHLLSI and the NAFDIDI for an extended summer season (1980e2013) 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.
Patrocinador: 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)
URI : http://hdl.handle.net/20.500.11765/7560
ISSN : 1352-2310
Colecciones: Artículos científicos 2015-2018

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