North African dust emissions and transport

Abstract. This study characterizes a massive African dust intrusion into the Caribbean Basin and southern U.S. in June 2020, which is nicknamed the Godzilla dust plume, using a comprehensive set of satellite and ground-based observations (including MODIS, CALIOP, SEVIRI, AERONET, and EPA Air Quality network) and the NASA GEOS global aerosol transport model. The MODIS data record registered this massive dust intrusion event as the most intense episode over the past two decades. During this event, the aerosol optical depth observed by AERONET and MODIS peaked at 3.5 off the coast of West Africa and 1.8 in the Caribbean Basin. CALIOP observations show that the top of dust plume reached altitudes of 6–8 km in West Africa and descended to about 4 km altitude over the Caribbean Basin and 2 km over the U.S. Gulf coast. The dust plume degraded the air quality in Puerto Rico to the hazardous level, with maximum daily PM10 concentration of 453 μg m−3 recorded on June 23. The dust intrusion into the U.S. raised the PM2.5 concentration on June 27 to a level exceeding the EPA air quality standard in about 40 % of the stations in the southern U.S. Satellite observations reveal that dust emissions from convection-generated haboobs and other sources in West Africa were large albeit not extreme on a daily basis. However, the anomalous strength and northern shift of the North Atlantic Subtropical High (NASH) together with the Azores low formed a closed circulation pattern that allowed for accumulation of the dust near the African coast for about four days. When the NASH was weakened and wandered back to south, the dust outflow region was dominated by a strong African Easterly Jet that rapidly transported the accumulated dust from the coastal region toward the Caribbean Basin, resulting in the record-breaking African dust intrusion. In comparison to satellite observations, the GEOS model well reproduced the MODIS observed tracks of the meandering dust plume as it was carried by the wind systems. However, the model substantially underestimated dust emissions from haboobs and did not lift up enough dust to the middle troposphere for ensuing long-range transport. Consequently, the model largely missed the satellite-observed elevated dust plume along the cross-ocean track and underestimated the dust intrusion into the Caribbean Basin by a factor of more than 4. Modeling improvements need to focus on developing more realistic representations of moist convection, haboobs, and the vertical transport of dust.

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Three North African dust source areas and their geochemical fingerprint

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2020.116645 ◽

2021 ◽

Vol 554 ◽

pp. 116645

Author(s):

Amy M. Jewell ◽

Nick Drake ◽

Anya J. Crocker ◽

Natalie L. Bakker ◽

Tereza Kunkelova ◽

...

Keyword(s):

North African ◽

Dust Source ◽

Source Areas ◽

African Dust ◽

Geochemical Fingerprint

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Changing nature of Saharan dust deposition in the Carpathian Basin (Central Europe): 40 years of identified North African dust events (1979–2018)

Environment International ◽

10.1016/j.envint.2020.105712 ◽

2020 ◽

Vol 139 ◽

pp. 105712 ◽

Cited By ~ 6

Author(s):

György Varga

Keyword(s):

Central Europe ◽

Carpathian Basin ◽

Saharan Dust ◽

Dust Deposition ◽

North African ◽

African Dust ◽

Dust Events

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The evolution of the North African dust plume over the past 15,000 years: Insights from dust fluxes measured along a meridional transect

Quaternary International ◽

10.1016/j.quaint.2012.08.893 ◽

2012 ◽

Vol 279-280 ◽

pp. 317

Author(s):

David McGee

Keyword(s):

North African ◽

The Past ◽

African Dust ◽

The North

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Diel variability of soluble Fe(II) and soluble total Fe in North African dust in the trade winds at Barbados

Journal of Geophysical Research Atmospheres ◽

10.1029/97jd01313 ◽

1997 ◽

Vol 102 (D17) ◽

pp. 21297-21305 ◽

Cited By ~ 136

Author(s):

X. R. Zhu ◽

J. M. Prospero ◽

F. J. Millero

Keyword(s):

North African ◽

Trade Winds ◽

African Dust ◽

Diel Variability

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Long-range transport of North African dust to the eastern United States

Journal of Geophysical Research Atmospheres ◽

10.1029/97jd00260 ◽

1997 ◽

Vol 102 (D10) ◽

pp. 11225-11238 ◽

Cited By ~ 203

Author(s):

Kevin D. Perry ◽

Thomas A. Cahill ◽

Robert A. Eldred ◽

Dabrina D. Dutcher ◽

Thomas E. Gill

Keyword(s):

United States ◽

Long Range ◽

Long Range Transport ◽

Eastern United States ◽

North African ◽

African Dust ◽

Range Transport

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Assessing Heatwaves and Their Association with North African Dust Intrusions in the Algarve (Portugal)

Atmosphere ◽

10.3390/atmos12091090 ◽

2021 ◽

Vol 12 (9) ◽

pp. 1090

Author(s):

Raquel Fernandes ◽

Marcelo Fragoso

Keyword(s):

Kendall Test ◽

Air Pollutant ◽

Simultaneous Occurrence ◽

North African ◽

African Dust ◽

Pollutant Concentrations ◽

Excess Heat Factor ◽

Dust Events ◽

Height Fields ◽

Air Pollutant Concentrations

Heatwaves are an extreme meteorological event in which affected populations may also be exposed to deteriorated air quality conditions due to the increase in air pollutant concentrations, such as PM10 (particulate matter < 10 µg/m3). In order to identify heatwaves (1973–2019) in the region of Faro (Algarve) during the hot season (April–September), the Excess Heat Factor (EHF) index was applied. The Mann–Kendall test revealed an upward trend in three heatwave metrics in Faro, and the trend of accumulated heat load (EHF load) was also positive as would be expected, but its signal was not statistically significant. An inventory of North African dust events (2006–2019) was made, and their simultaneous occurrence with heatwaves was assessed, pointing to only 20% of dust events of the Sahara occurring simultaneously with heatwave days. A cluster analysis was conducted on daily geopotential height fields at 850 hPa level over the 2006–2019 period, and four distinct patterns were identified as the most prominent synoptic circulations promoting both heatwave conditions and North African dust over the Algarve.

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Apparent dust size discrepancy in aerosol reanalysis in north African dust after long-range transport

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-10047-2020 ◽

2020 ◽

Vol 20 (16) ◽

pp. 10047-10062 ◽

Cited By ~ 1

Author(s):

Samantha J. Kramer ◽

Claudia Alvarez ◽

Anne E. Barkley ◽

Peter R. Colarco ◽

Lillian Custals ◽

...

Keyword(s):

Aerosol Optical Depth ◽

Long Range ◽

Optical Depth ◽

Dust Particles ◽

Long Range Transport ◽

North African ◽

African Dust ◽

Range Transport ◽

Dust Mass ◽

Mass Concentrations

Abstract. North African dust reaches the southeastern United States every summer. Size-resolved dust mass measurements taken in Miami, Florida, indicate that more than one-half of the surface dust mass concentrations reside in particles with geometric diameters less than 2.1 µm, while vertical profiles of micropulse lidar depolarization ratios show dust reaching above 4 km during pronounced events. These observations are compared to the representation of dust in the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) aerosol reanalysis and closely related Goddard Earth Observing System model version 5 (GEOS-5) Forward Processing (FP) aerosol product, both of which assimilate satellite-derived aerosol optical depths using a similar protocol and inputs. These capture the day-to-day variability in aerosol optical depth well, in a comparison to an independent sun-photometer-derived aerosol optical depth dataset. Most of the modeled dust mass resides in diameters between 2 and 6 µm, in contrast to the measurements. Model-specified mass extinction efficiencies equate light extinction with approximately 3 times as much aerosol mass, in this size range, compared to the measured dust sizes. GEOS-5 FP surface-layer sea salt mass concentrations greatly exceed observed values, despite realistic winds and relative humidities. In combination, these observations help explain why, despite realistic total aerosol optical depths, (1) free-tropospheric model volume extinction coefficients are lower than those retrieved from the micro-pulse lidar, suggesting too-low model dust loadings in the free troposphere, and (2) model dust mass concentrations near the surface can be higher than those measured. The modeled vertical distribution of dust, when captured, is reasonable. Large, aspherical particles exceeding the modeled dust sizes are also occasionally present, but dust particles with diameters exceeding 10 µm contribute little to the measured total dust mass concentrations after such long-range transport. Remaining uncertainties warrant a further integrated assessment to confirm this study's interpretations.

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Apparent dust size discrepancy in aerosol reanalysis in north African dust after long-range transport

10.5194/acp-2020-1 ◽

2020 ◽

Cited By ~ 1

Author(s):

Samantha J. Kramer ◽

Claudia Alvarez ◽

Anne Barkley ◽

Peter R. Colarco ◽

Lillian Custals ◽

...

Keyword(s):

Aerosol Optical Depth ◽

Long Range ◽

Optical Depth ◽

Long Range Transport ◽

North African ◽

Surface Dust ◽

African Dust ◽

Range Transport ◽

Dust Mass ◽

Mass Concentrations

Abstract. North African dust reaches the southeast United States every summer. Measurements taken in Miami, Florida indicate that more than one-half of the surface dust mass concentrations reside in particles with diameters less than 2.1 μm, while vertical profiles of micropulse lidar depolarization ratios show dust reaching above four km during pronounced events. These observations are compared to the representation of dust in the MERRA-2 aerosol reanalysis and closely-related GEOS-5 Forward Processing (FP) aerosol product, both of which assimilate satellite-derived aerosol optical depths using a similar protocol and inputs. These capture the day-to-day variability in aerosol optical depth well, in a comparison to an independent sun-photometer-derived aerosol optical depth dataset. Measured near-surface dust mass concentrations slightly exceed model values, with most of the modeled dust mass in diameters between 2–6 μm. Modeled-specified mass extinction efficiencies equate light extinction with approximately three times as much aerosol mass, in this size range, compared to the measured dust sizes. GEOS-5 FP surface-layer sea salt mass concentrations greatly exceed observed values, despite realistic winds and relative humidities. In combination, these observations help explain, why, despite realistic total aerosol optical depths, 1) free-tropospheric model volume extinction coefficients are lower than those retrieved from the micro-pulse lidar, suggesting too low model dust loadings, and 2) model dust mass concentrations near the surface are higher than those measured. The modeled vertical distribution of dust, when captured, is reasonable. Large, aspherical particles exceeding the modeled dust sizes are also occasionally present, but dust particles with diameters exceeding ten μm contribute little to the measured total dust mass concentrations after such long-range transport. A further integrated assessment is needed to confirm this study's interpretations.

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