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.

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 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 Modeling regional aerosol variability over California and its sensitivity to emissions and long-range transport during the 2010 CalNex and CARES campaigns

2014 ◽  
Vol 14 (6) ◽  
pp. 7187-7303 ◽  
Author(s):  
J. D. Fast ◽  
J. Allan ◽  
R. Bahreini ◽  
J. Craven ◽  
L. Emmons ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Aerosol Optical Depth ◽  
Long Range ◽  
Optical Depth ◽  
Trace Gases ◽  
Organic Aerosol ◽  
Global Model ◽  
Long Range Transport ◽  
Anthropogenic Emissions ◽  
Range Transport

Abstract. The performance of the Weather Research and Forecasting regional model with chemistry (WRF-Chem) in simulating the spatial and temporal variations in aerosol mass, composition, and size over California is quantified using measurements collected during the California Nexus of Air Quality and Climate Experiment (CalNex) and the Carbonaceous Aerosol and Radiative Effects Study (CARES) conducted during May and June of 2010. The extensive meteorological, trace gas, and aerosol measurements collected at surface sites and along aircraft and ship transects during CalNex and CARES were combined with operational monitoring network measurements to create a single dataset that was used to evaluate the one configuration of the model. Simulations were performed that examined the sensitivity of regional variations in aerosol concentrations to anthropogenic emissions and to long-range transport of aerosols into the domain obtained from a global model. The configuration of WRF-Chem used in this study is shown to reproduce the overall synoptic conditions, thermally-driven circulations, and boundary layer structure observed in region that controls the transport and mixing of trace gases and aerosols. However, sub-grid scale variability in the meteorology and emissions as well as uncertainties in the treatment of secondary organic aerosol chemistry likely contribute to errors at a primary surface sampling site located at the edge of the Los Angeles basin. Differences among the sensitivity simulations demonstrate that the aerosol layers over the central valley detected by lidar measurements likely resulted from lofting and recirculation of local anthropogenic emissions along the Sierra Nevada. Reducing the default emissions inventory by 50% led to an overall improvement in many simulated trace gases and black carbon aerosol at most sites and along most aircraft flight paths; however, simulated organic aerosol was closer to observed when there were no adjustments to the primary organic aerosol emissions. The model performance for some aerosol species was not uniform over the region, and we found that sulfate was better simulated over northern California whereas nitrate was better simulated over southern California. While the overall spatial and temporal variability of aerosols and their precursors were simulated reasonably well, we show cases where the local transport of some aerosol plumes were either too slow or too fast, which adversely affects the statistics regarding the differences between observed and simulated quantities. Comparisons with lidar and in-situ measurements indicate that long-range transport of aerosols from the global model was likely too high in the free troposphere even though their concentrations were relatively low. This bias led to an over-prediction in aerosol optical depth by as much as a factor of two that offset the under-predictions of boundary-layer extinction resulting primarily from local emissions. Lowering the boundary conditions of aerosol concentrations by 50% greatly reduced the bias in simulated aerosol optical depth for all regions of California. This study shows that quantifying regional-scale variations in aerosol radiative forcing and determining the relative role of emissions from local and distant sources is challenging during "clean" conditions and that a wide array of measurements are needed to ensure model predictions are correct for the right reasons. In this regard, the combined CalNex and CARES datasets are an ideal testbed that can be used to evaluate aerosol models in great detail and develop improved treatments for aerosol processes.

scholarly journals Modeling regional aerosol and aerosol precursor variability over California and its sensitivity to emissions and long-range transport during the 2010 CalNex and CARES campaigns

2014 ◽  
Vol 14 (18) ◽  
pp. 10013-10060 ◽  
Author(s):  
J. D. Fast ◽  
J. Allan ◽  
R. Bahreini ◽  
J. Craven ◽  
L. Emmons ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Air Quality ◽  
Aerosol Optical Depth ◽  
Long Range ◽  
Optical Depth ◽  
Trace Gases ◽  
Organic Aerosol ◽  
Long Range Transport ◽  
Range Transport ◽  
Aerosol Radiative

Abstract. The performance of the Weather Research and Forecasting regional model with chemistry (WRF-Chem) in simulating the spatial and temporal variations in aerosol mass, composition, and size over California is quantified using the extensive meteorological, trace gas, and aerosol measurements collected during the California Nexus of Air Quality and Climate Experiment (CalNex) and the Carbonaceous Aerosol and Radiative Effects Study (CARES) conducted during May and June of 2010. The overall objective of the field campaigns was to obtain data needed to better understand processes that affect both climate and air quality, including emission assessments, transport and chemical aging of aerosols, aerosol radiative effects. Simulations were performed that examined the sensitivity of aerosol concentrations to anthropogenic emissions and to long-range transport of aerosols into the domain obtained from a global model. The configuration of WRF-Chem used in this study is shown to reproduce the overall synoptic conditions, thermally driven circulations, and boundary layer structure observed in region that controls the transport and mixing of trace gases and aerosols. Reducing the default emissions inventory by 50% led to an overall improvement in many simulated trace gases and black carbon aerosol at most sites and along most aircraft flight paths; however, simulated organic aerosol was closer to observed when there were no adjustments to the primary organic aerosol emissions. We found that sulfate was better simulated over northern California whereas nitrate was better simulated over southern California. While the overall spatial and temporal variability of aerosols and their precursors were simulated reasonably well, we show cases where the local transport of some aerosol plumes were either too slow or too fast, which adversely affects the statistics quantifying the differences between observed and simulated quantities. Comparisons with lidar and in situ measurements indicate that long-range transport of aerosols from the global model was likely too high in the free troposphere even though their concentrations were relatively low. This bias led to an over-prediction in aerosol optical depth by as much as a factor of 2 that offset the under-predictions of boundary-layer extinction resulting primarily from local emissions. Lowering the boundary conditions of aerosol concentrations by 50% greatly reduced the bias in simulated aerosol optical depth for all regions of California. This study shows that quantifying regional-scale variations in aerosol radiative forcing and determining the relative role of emissions from local and distant sources is challenging during `clean' conditions and that a wide array of measurements are needed to ensure model predictions are correct for the right reasons. In this regard, the combined CalNex and CARES data sets are an ideal test bed that can be used to evaluate aerosol models in great detail and develop improved treatments for aerosol processes.

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

Is Summer African Dust Arriving Earlier to Barbados? The Updated Long-Term In Situ Dust Mass Concentration Time Series from Ragged Point, Barbados, and Miami, Florida

2019 ◽  
Vol 100 (10) ◽  
pp. 1981-1986 ◽  
Author(s):  
Paquita Zuidema ◽  
Claudia Alvarez ◽  
Samantha J. Kramer ◽  
Lillian Custals ◽  
Miguel Izaguirre ◽  
...  
Keyword(s):  
Time Series ◽  
Mass Concentration ◽  
North African ◽  
African Dust ◽  
Dust Mass ◽  
Intercontinental Transport ◽  
Concentration Time Series ◽  
Mass Concentrations

AbstractSurface dust mass concentrations, extracted from filters collected at Miami, Florida, and Ragged Point, Barbados, since 1974 and 1973, respectively, provide a rare, unusual, and important metric of the intercontinental transport of North African dust. The daily-resolved time series, updated through December 2018 for Miami and through December 2015 along with May–September 2016 and January–March and June–August 2017 for Barbados, indicate summer-mean dust mass concentrations have mostly decreased this decade at Miami, but not at Barbados, where instead the events containing the highest dust mass concentration events may be shifting to earlier in the year.

scholarly journals Chemical characterization and sources of submicron aerosols in the northeastern Qinghai-Tibet Plateau: insights from high-resolution mass spectrometry

2019 ◽  
Author(s):  
Xinghua Zhang ◽  
Jianzhong Xu ◽  
Shichang Kang ◽  
Qi Zhang
Keyword(s):  
High Resolution ◽  
Long Range ◽  
Biomass Burning ◽  
Tibet Plateau ◽  
Source Analysis ◽  
Long Range Transport ◽  
Aerosol Mass ◽  
Range Transport ◽  
Qinghai Tibet Plateau ◽  
Mass Concentrations

Abstract. An Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) was deployed along with other online instruments to study the highly time-resolved chemistry and sources of submicron aerosols (PM1) at Waliguan (WLG) Baseline Observatory, a high-altitude (3816 m a.s.l.) background station located at the northeastern edge of Qinghai-Tibet Plateau (QTP), during 1–31 July 2017. The average PM1 mass concentration during this study was 9.1 μg m−3 (ranging from 0.3 to 28.1 μg m−3), which was distinct higher than those (2.0–5.7 μg m−3) measured with Aerodyne AMS at other high-elevation sites in the southern or central QTP. Sulfate showed dominant contribution (38.1 %) to PM1 at WLG following by organics (34.5 %), ammonium (15.2 %), nitrate (8.1 %), BC (3.0 %) and chloride (1.1 %). Accordingly, bulk aerosols appeared to be slightly acidic throughout this study mainly related to the enhanced sulfate contribution. All chemical species peaked at the accumulation mode, indicating the well mixed and highly aged aerosol particles at WLG from long-range transport. Positive matrix factorization (PMF) on the high-resolution organic mass spectra resolved four distinct organic aerosol (OA) components, including a traffic-related hydrocarbon-like OA (HOA), a relatively fresh biomass burning OA (BBOA), an aged biomass burning OA (agBBOA) and a more-oxidized oxygenated OA (OOA). On average, the two relatively oxidized OAs, OOA and agBBOA, contributed 34.4 % and 40.4 % of organics, respectively, while the rest were 18.4 % for BBOA and 6.8 % for HOA. Source analysis for air masses displayed higher mass concentrations of PM1 and enhanced contributions of sulfate and biomass burning related OA components (agBBOA + BBOA) were from northeast of the WLG with shorter transport distance, whereas lower PM1 mass concentrations with enhanced OOA contribution were from west after long-range transport, suggesting their distinct aerosol sources and significant impacts of regional transport to aerosol mass loadings and chemistry at WLG.

scholarly journals Dust Storm Event of February 2019 in Central and East Coast of Australia and Evidence of Long-Range Transport to New Zealand and Antarctica

2019 ◽  
Author(s):  
Hiep Duc Nguyen ◽  
Matthew Riley ◽  
John Leys ◽  
David Salter
Keyword(s):  
New Zealand ◽  
Aerosol Optical Depth ◽  
Long Range ◽  
Dust Storm ◽  
Long Range Transport ◽  
Storm Event ◽  
Tasman Sea ◽  
Range Transport ◽  
Dust Storm Event ◽  
Central Australia

Between 11 to 15 February 2019, a dust storm originating from Central Australia with persistent westerly and south westerly winds caused high particles concentration at many sites in the state of New South Wales (NSW), both inland and along the coast. The dust continued on to New Zealand and to Antarctica in the south east. This study uses observed data from air quality monitoring stations in NSW and New Zealand, MODIS 3km AOD (Aerosol Optical Depth) product from Terra/Aqua and lidar aerosol profile from CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite data, and the Weather Research Forecast WRF-Chem model based on GOCART-AFWA (Goddard Chemistry Aerosol Radiation and Transport – Air Force and Weather Agency) dust scheme and GOCART aerosol and gas-phase MOZART (Model for Ozone And Related chemical Tracers) chemistry model to study the long-range transport of aerosols for the period 11 to 15 February 2019 across eastern Australia and onto New Zealand and Antarctica. Wild fires also happened in northern NSW at the same time and their emissions are taken into account in WRF-Chem model by using Fire Inventory from NCAR (FINN) as emission input. Modelling results by the WRF-Chem model show that for the Canterbury region of South Island of New Zealand, peak concentration of PM10 (and PM2.5) as measured on 14 February 2019 at 05:00 UTC at the monitoring stations of Geraldine, Ashburton, Timaru and Woolston (Christchurch), which are more than 100km from each other and at Rangiora, Kaiapoi about 2 hours later, correspond to the prediction of high PM10 due to intrusion of dust to ground level from transported dust layer above. The Aerosol Optical Depth (AOD) observation data from MODIS Terra/Aqua and CALIOP lidar measurements on board CALIPSO satellite also indicate that high altitude of dust, originated from this dust storm event in Australia, was located above Antarctica. This study suggests that at present dust storms in Australia can transport dust from sources in Central Australia to the Tasman sea, New Zealand and Antarctica. This process has been going on for at least the last 170k years as indicated by dust found in ice cores from Antarctica and sediment records in the Tasman Sea.

scholarly journals Horizontal variability of aerosol optical depth observed during the ARCTAS airborne experiment

2011 ◽  
Vol 11 (5) ◽  
pp. 16245-16264 ◽  
Author(s):  
Y. Shinozuka ◽  
J. Redemann
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Satellite Remote Sensing ◽  
Wavelength Dependence ◽  
Long Range Transport ◽  
Straight Line ◽  
Relative Standard ◽  
Range Transport ◽  
Local Emissions ◽  
Airborne Experiment

Abstract. We present statistics on the horizontal variability of aerosol optical depth (AOD) directly measured from the NASA P-3 aircraft. Our measurements during two contrasting phases (in Alaska and Canada) of the ARCTAS mission arguably constrain the variability in most aerosol environments common over the globe. In the Canada phase, which features local emissions, 499 nm AOD has a median relative standard deviation (stdrel,med) of 19 % and 9 % and an autocorrelation (r) of 0.37 and 0.71 over 20 km and 6 km horizontal segments, respectively. In the Alaska phase, which features long-range transport, the variability is considerably lower (stdrel,med = 3 %, r = 0.92 even over 35.2 km). Compared to the magnitude of AOD, its wavelength dependence varies less in the Canada phase, more in the Alaska phase. We translate these findings from straight-line flight tracks into grid boxes and points, to help interpretation and design of satellite remote sensing, suborbital observations and transport modeling.

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