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

1997 ◽  
Vol 102 (D10) ◽  
pp. 11225-11238 ◽  
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

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

2020 ◽  
Vol 20 (16) ◽  
pp. 10047-10062 ◽  
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.

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

2020 ◽  
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.

An investigation of long-range transport of ozone across the midwestern and eastern united states

1977 ◽  
Vol 11 (9) ◽  
pp. 797-802 ◽  
Author(s):  
George T. Wolff ◽  
Paul J. Lioy ◽  
Gregory D. Wight ◽  
Ronald E. Meyers ◽  
Richard T. Cederwall
Keyword(s):  
United States ◽  
Long Range ◽  
Long Range Transport ◽  
Eastern United States ◽  
Range Transport

Individual particle characteristics of North African dust under different long-range transport scenarios

2009 ◽  
Vol 43 (11) ◽  
pp. 1850-1863 ◽  
Author(s):  
Esther Coz ◽  
Francisco J. Gómez-Moreno ◽  
Manuel Pujadas ◽  
Gary S. Casuccio ◽  
Traci L. Lersch ◽  
...  
Keyword(s):  
Long Range ◽  
Individual Particle ◽  
Long Range Transport ◽  
North African ◽  
African Dust ◽  
Particle Characteristics ◽  
Range Transport

scholarly journals Inconsistent decadal variations between surface and free tropospheric nitrogen oxides over United States

2017 ◽  
Author(s):  
Zhe Jiang ◽  
Helen Worden ◽  
John R. Worden ◽  
Daven K. Henze ◽  
Dylan B. A. Jones ◽  
...  
Keyword(s):  
United States ◽  
Air Quality ◽  
Nitrogen Oxides ◽  
Climate Variability ◽  
Long Range ◽  
North American ◽  
Long Range Transport ◽  
Substantial Impact ◽  
Decadal Scale ◽  
Range Transport

Abstract. Decreases in surface emissions of nitrogen oxides (NOx = NO + NO2) in North America have led to substantial improvements in air-quality over the last several decades. Here we show that satellite observations of tropospheric nitrogen dioxide (NO2) columns over the contiguous United States (US) do not decrease after about 2009, while surface NO2 concentrations continue to decline through to the present. This divergence, if it continues, could have a substantial impact on surface air quality due to mixing of free-tropospheric air into the boundary layer. Our results show only limited contributions from local effects such as fossil fuel emissions, lightning, or instrument artifacts, but we do find a possible relationship of NO2 changes to decadal climate variability. Our analysis demonstrates that the intensity of transpacific transport is stronger in El Niño years and weaker in La Niña years, and consequently, that decadal-scale climate variability impacts the contribution of Asian emissions on North American atmospheric composition. Because of the short lifetime, it is usually believed that the direct contribution of long-range transport to tropospheric NOx distribution is limited. If our hypothesis about transported Asian emissions is correct, then this observed divergence between satellite and surface NOx could indicate mechanisms that allow for either NOx or its reservoir species to have a larger than expected effect on North American tropospheric composition. These results therefore suggest more aircraft and satellite studies to determine the possible missing processes in our understanding of the long-range transport of tropospheric NOx.

Air Quality Forecast Verification Using Satellite Data

2008 ◽  
Vol 47 (2) ◽  
pp. 425-442 ◽  
Author(s):  
S. Kondragunta ◽  
P. Lee ◽  
J. McQueen ◽  
C. Kittaka ◽  
A. I. Prados ◽  
...  
Keyword(s):  
United States ◽  
Air Quality ◽  
Long Range ◽  
Regional Scale ◽  
The United States ◽  
Long Range Transport ◽  
Forecast Performance ◽  
Air Quality Forecast ◽  
Time Period ◽  
Range Transport

Abstract NOAA’s operational geostationary satellite retrievals of aerosol optical depths (AODs) were used to verify National Weather Service developmental (research mode) particulate matter (PM2.5) predictions tested during the summer 2004 International Consortium for Atmospheric Research on Transport and Transformation/New England Air Quality Study (ICARTT/NEAQS) field campaign. The forecast period included long-range transport of smoke from fires burning in Canada and Alaska and a regional-scale sulfate event over the Gulf of Mexico and the eastern United States. Over the 30-day time period for which daytime hourly forecasts were compared with observations, the categorical (exceedance defined as AOD > 0.55) forecast accuracy was between 0% and 20%. Hourly normalized mean bias (forecasts − observations) ranged between −50% and +50% with forecasts being positively biased when observed AODs were small and negatively biased when observed AODs were high. Normalized mean errors are between 50% and 100% with the errors on the lower end during the 18–22 July 2004 time period when a regional-scale sulfate event occurred. Spatially, the errors are small over the regions where sulfate plumes were present. The correlation coefficient also showed similar features (spatially and temporally) with a peak value of ∼0.6 during the 18–22 July 2004 time period. The dominance of long-range transport of smoke into the United States during the summer of 2004, neglected in the model predictions, skewed the model forecast performance. Enhanced accuracy and reduced normalized mean errors during the time period when a sulfate event prevailed show that the forecast system has skill in predicting PM2.5 associated with urban/industrial pollution events.

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