scholarly journals Aerosol Optical Depth of the Main Aerosol Species over Italian Cities Based on the NASA/MERRA-2 Model Reanalysis

Atmosphere ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 709 ◽  
Author(s):  
Umberto Rizza ◽  
Enrico Mancinelli ◽  
Mauro Morichetti ◽  
Giorgio Passerini ◽  
Simone Virgili
Keyword(s):  
Air Quality ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Transport Model ◽  
Urban Air Pollution ◽  
Sea Salt ◽  
Anthropogenic Aerosols ◽  
National Scale ◽  
Global Coverage ◽  
Modern Era

The Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) provides data at 0.5° × 0.625° resolution covering a period from 1 January 1980 to the present. Natural and anthropogenic aerosols are simulated in MERRA-2, considering the Goddard chemistry, aerosol, radiation, and transport model. This model simulates the sources, sinks, and chemistry of mixed aerosol tracers: dust, sea salt, hydrophobic and hydrophilic black carbon and organic carbon, and sulfate. MERRA-2 aerosol reanalysis is a pioneering tool for investigating air quality issues, noteworthy for its global coverage and its distinction of aerosol speciation expressed in the form of aerosol optical depth (AOD). The aim of this work was to use the MERRA-2 reanalysis to study urban air pollution at a national scale by analyzing the AOD. AOD trends were evaluated for a 30-year period (1987–2017) over five Italian cities (Milan, Rome, Cagliari, Taranto, and Palermo) in order to investigate the impacts of urbanization, industrialization, air quality regulations, and regional transport on urban aerosol load. AOD evolution predicted by the MERRA-2 model in the period 2002–2017 showed a generalized decreasing trend over the selected cities. The anthropogenic signature on total AOD was between 50% and 80%, with the largest contribution deriving from sulfate.

scholarly journals The European aerosol budget in 2006

2010 ◽  
Vol 10 (9) ◽  
pp. 21391-21437 ◽  
Author(s):  
J. M. J. Aan de Brugh ◽  
M. Schaap ◽  
E. Vignati ◽  
F. Dentener ◽  
M. Kahnert ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Transport Model ◽  
Ground Level ◽  
Sea Salt ◽  
Optical Measurements ◽  
Aerosol Size Distribution ◽  
Anthropogenic Aerosols ◽  
Removal Rates ◽  
Wet Removal

Abstract. This paper presents the aerosol budget over Europe in 2006 calculated with the global transport model TM5 coupled to the size-resolved aerosol module M7. Comparison with ground observations indicates that the model reproduces the observed concentrations quite well with an expected slight underestimation of PM10 due to missing emissions (e.g. resuspension). We observe that a little less than half of the anthropogenic aerosols emitted in Europe are exported and the rest is removed by deposition. The anthropogenic aerosols are removed mostly by rain (95%) and only 5% is removed by dry deposition. For the larger natural aerosols, especially sea salt, a larger fraction is removed by dry processes (sea salt: 70%, mineral dust: 35%). We observe transport of aerosols in the jet stream in the higher atmosphere and an import of Sahara dust from the south at high altitudes. Comparison with optical measurements shows that the model reproduces the Ångström parameter very well, which indicates a correct simulation of the aerosol size distribution. However, we observe an underestimation of the aerosol optical depth. Because the surface concentrations are close to the observations, the shortage of aerosol in the model is probably at higher altitudes. We show that the discrepancies are mainly caused by an overestimation of wet-removal rates. To match the observations, the wet-removal rates have to be scaled down by a factor of about 5. In that case the modelled ground-level concentrations of sulphate and sea salt increase by 50% (which deteriorates the match), while other components stay roughly the same. Finally, it is shown that in particular events, improved fire emission estimates may significantly improve the ability of the model to simulate the aerosol optical depth. We stress that discrepancies in aerosol models can be adequately analysed if all models would provide (regional) aerosol budgets, as presented in the current study.

scholarly journals The European aerosol budget in 2006

2011 ◽  
Vol 11 (3) ◽  
pp. 1117-1139 ◽  
Author(s):  
J. M. J. Aan de Brugh ◽  
M. Schaap ◽  
E. Vignati ◽  
F. Dentener ◽  
M. Kahnert ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Transport Model ◽  
Ground Level ◽  
Sea Salt ◽  
Optical Measurements ◽  
Aerosol Size Distribution ◽  
Anthropogenic Aerosols ◽  
Removal Rates ◽  
Wet Removal

Abstract. This paper presents the aerosol budget over Europe in 2006 calculated with the global transport model TM5 coupled to the size-resolved aerosol module M7. Comparison with ground observations indicates that the model reproduces the observed concentrations quite well with an expected slight underestimation of PM10 due to missing emissions (e.g. resuspension). We model that a little less than half of the anthropogenic aerosols emitted in Europe are exported and the rest is removed by deposition. The anthropogenic aerosols are removed mostly by rain (95%) and only 5% is removed by dry deposition. For the larger natural aerosols, especially sea salt, a larger fraction is removed by dry processes (sea salt: 70%, mineral dust: 35%). We model transport of aerosols in the jet stream in the higher atmosphere and an import of Sahara dust from the south at high altitudes. Comparison with optical measurements shows that the model reproduces the Ångström parameter very well, which indicates a correct simulation of the aerosol size distribution. However, we underestimate the aerosol optical depth. Because the surface concentrations are close to the observations, the shortage of aerosol in the model is probably at higher altitudes. We show that the discrepancies are mainly caused by an overestimation of wet-removal rates. To match the observations, the wet-removal rates have to be scaled down by a factor of about 5. In that case the modelled ground-level concentrations of sulphate and sea salt increase by 50% (which deteriorates the match), while other components stay roughly the same. Finally, it is shown that in particular events, improved fire emission estimates may significantly improve the ability of the model to simulate the aerosol optical depth. We stress that discrepancies in aerosol models can be adequately analysed if all models would provide (regional) aerosol budgets, as presented in the current study.

scholarly journals Modelling of nitrate and ammonium-containing aerosols in presence of sea salt

2006 ◽  
Vol 6 (12) ◽  
pp. 4809-4821 ◽  
Author(s):  
G. Myhre ◽  
A. Grini ◽  
S. Metzger
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Radiative Forcing ◽  
Transport Model ◽  
Meteorological Condition ◽  
Global Scale ◽  
Sea Salt ◽  
Aerosol Composition ◽  
Fine Mode ◽  
High Concentrations

Abstract. A thermodynamical model for treatment of gas/aerosol partitioning of semi volatile inorganic aerosols has been implemented in a global chemistry and aerosol transport model (Oslo CTM2). The sulphur cycle and sea salt particles have been implemented earlier in the Oslo CTM2 and the focus of this study is on nitrate partitioning to the aerosol phase and if particulate nitrate is expected to form in fine or coarse mode aerosols. Modelling of the formation of fine mode nitrate particles is complicated since it depends on other aerosol components and aerosol precursors as well as meteorological condition. The surface concentrations from the model are compared to observed surface concentrations at around 20 sites around Europe for nitrate and ammonium. The agreement for nitrate is good but the modelled values are somewhat underestimated compared to observations at high concentrations, whereas for ammonium the agreement is very good. However, we underscore that such a comparison is not of large importance for the aerosol optical depth of particulate nitrate since the vertical profile of aerosol components and their precursors are so important. Fine mode nitrate formation depends on vertical profiles of both ammonia/ammonium and sulphate. The model results show that fine mode particulate nitrate play a non-negligible role in the total aerosol composition in certain industrialized regions and therefore have a significant local radiative forcing. On a global scale the aerosol optical depth of fine mode nitrate is relatively small due to limited availability of ammonia and loss to larger sea salt particles. Inclusion of sea salt in the calculations reduces the aerosol optical depth and burden of fine mode nitrate by 25% on a global scale but with large regional variations.

scholarly journals A comparison of sea salt emission parameterizations in northwestern Europe using a chemistry transport model setup

2016 ◽  
Vol 16 (15) ◽  
pp. 9905-9933 ◽  
Author(s):  
Daniel Neumann ◽  
Volker Matthias ◽  
Johannes Bieser ◽  
Armin Aulinger ◽  
Markus Quante
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Wet Deposition ◽  
Transport Model ◽  
Deposition Velocity ◽  
Sea Salt ◽  
The North ◽  
Shaped Particle ◽  
The North Sea ◽  
Model Setup

Abstract. Atmospheric sea salt particles affect chemical and physical processes in the atmosphere. These particles provide surface area for condensation and reaction of nitrogen, sulfur, and organic species and are a vehicle for the transport of these species. Additionally, HCl is released from sea salt. Hence, sea salt has a relevant impact on air quality, particularly in coastal regions with high anthropogenic emissions, such as the North Sea region. Therefore, the integration of sea salt emissions in modeling studies in these regions is necessary. However, it was found that sea salt concentrations are not represented with the necessary accuracy in some situations.In this study, three sea salt emission parameterizations depending on different combinations of wind speed, salinity, sea surface temperature, and wave data were implemented and compared: GO03 (Gong, 2003), SP13 (Spada et al., 2013), and OV14 (Ovadnevaite et al., 2014). The aim was to identify the parameterization that most accurately predicts the sea salt mass concentrations at different distances to the source regions. For this purpose, modeled particle sodium concentrations, sodium wet deposition, and aerosol optical depth were evaluated against measurements of these parameters. Each 2-month period in winter and summer 2008 were considered for this purpose. The shortness of these periods limits generalizability of the conclusions on other years.While the GO03 emissions yielded overestimations in the PM10 concentrations at coastal stations and underestimations of those at inland stations, OV14 emissions conversely led to underestimations at coastal stations and overestimations at inland stations. Because of the differently shaped particle size distributions of the GO03 and OV14 emission cases, the deposition velocity of the coarse particles differed between both cases which yielded this distinct behavior at inland and coastal stations. The PM10 concentrations produced by the SP13 emissions generally overestimated the measured concentrations. The sodium wet deposition was generally underestimated by the model simulations but the SP13 cases yielded the least underestimations. Because the model tends to underestimate wet deposition, this result needs to be considered critically. Measurements of the aerosol optical depth (AOD) were underestimated by all model cases in the summer and partly in winter. None of the model cases clearly improved the modeled AODs. Overall, GO03 and OV14 produced the most accurate results, but both parameterizations revealed weaknesses in some situations.

scholarly journals Modelling of nitrate particles: importance of sea salt

2006 ◽  
Vol 6 (1) ◽  
pp. 1455-1480 ◽  
Author(s):  
G. Myhre ◽  
A. Grini
Keyword(s):  
Ammonium Nitrate ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Radiative Forcing ◽  
Transport Model ◽  
Global Scale ◽  
Sea Salt ◽  
Aerosol Composition ◽  
Inorganic Aerosols ◽  
Fine Mode

Abstract. A thermo dynamical model for treatment of gas/aerosol partitioning of semi volatile inorganic aerosols has been implemented in a global chemistry and aerosol transport model (Oslo CTM2). The sulphur cycle and sea salt particles have been implemented earlier in the Oslo CTM2 and the focus of this study is on whether nitrate particles are formed as fine mode ammonium nitrate or react on existing sea salt particles. The model results show that ammonium nitrate particles play a non-negligible role in the total aerosol composition in certain industrialized regions and therefore have a significant local radiative forcing. On a global scale the aerosol optical depth of ammonium nitrate is relatively small due to limited availability of ammonia and reaction with sea salt particles. Inclusion of sea salt in the calculations reduces the aerosol optical depth and burden of ammonium nitrate particles by 25% on a global scale but with large regional variations.

scholarly journals Monitoring the Spatial Variation of Aerosol Optical Depth and Its Correlation with Land Use/Land Cover in Wuhan, China: A Perspective of Urban Planning

2021 ◽  
Vol 18 (3) ◽  
pp. 1132
Author(s):  
Qijiao Xie ◽  
Qi Sun
Keyword(s):  
Land Use ◽  
Air Quality ◽  
Urban Planning ◽  
Land Cover ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Water Bodies ◽  
Landsat 8 ◽  
Land Use Land Cover ◽  
The Impact

Aerosols significantly affect environmental conditions, air quality, and public health locally, regionally, and globally. Examining the impact of land use/land cover (LULC) on aerosol optical depth (AOD) helps to understand how human activities influence air quality and develop suitable solutions. The Landsat 8 image and Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol products in summer in 2018 were used in LULC classification and AOD retrieval in this study. Spatial statistics and correlation analysis about the relationship between LULC and AOD were performed to examine the impact of LULC on AOD in summer in Wuhan, China. Results indicate that the AOD distribution expressed an obvious “basin effect” in urban development areas: higher AOD values concentrated in water bodies with lower terrain, which were surrounded by the high buildings or mountains with lower AOD values. The AOD values were negatively correlated with the vegetated areas while positively correlated to water bodies and construction lands. The impact of LULC on AOD varied with different contexts in all cases, showing a “context effect”. The regression correlations among the normalized difference vegetation index (NDVI), normalized difference built-up index (NDBI), normalized difference water index (NDWI), and AOD in given landscape contexts were much stronger than those throughout the whole study area. These findings provide sound evidence for urban planning, land use management and air quality improvement.

scholarly journals Airborne observation during KORUS-AQ show aerosol optical depth are more spatially self-consistent than aerosol intensive properties

2022 ◽  
Author(s):  
Samuel E. LeBlanc ◽  
Michal Segal-Rozenhaimer ◽  
Jens Redemann ◽  
Connor J. Flynn ◽  
Roy R. Johnson ◽  
...  
Keyword(s):  
Air Quality ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Temporal Variability ◽  
Spatial Scales ◽  
Aerosol Emission ◽  
Fine Mode ◽  
Predominant Factor ◽  
Spatio Temporal ◽  
Microphysical Processes

Abstract. Aerosol particles can be emitted, transported, removed, or transformed, leading to aerosol variability at scales impacting the climate (days to years and over hundreds of kilometers) or the air quality (hours to days and from meters to hundreds of kilometers). We present the temporal and spatial scales of changes in AOD (Aerosol Optical Depth), and aerosol size (using Angstrom Exponent; AE, and Fine-Mode-Fraction; FMF) over Korea during the 2016 KORUS-AQ (KORea-US Air Quality) atmospheric experiment. We use measurements and retrievals of aerosol optical properties from airborne instruments for remote sensing (4STAR; Spectrometers for Sky-Scanning Sun Tracking Atmospheric Research) and in situ (LARGE; NASA Langley Aerosol Research Group Experiment) on board the NASA DC-8, geostationary satellite (GOCI; Geostationary Ocean Color Imager; Yonsei aerosol retrieval (YAER) version 2) and reanalysis (MERRA-2; Modern-Era Retrospective Analysis for Research and Applications, version 2). Measurements from 4STAR when flying below 500 m, show an average AOD at 501 nm of 0.43 and an average AE of 1.15 with large standard deviation (0.32 and 0.26 for AOD and AE respectively) likely due to mixing of different aerosol types (fine and coarse mode). The majority of AODs due to fine mode aerosol is observed at altitudes lower than 2 km. Even though there are large variations, for 18 out of the 20 flight days, the column AOD measurements by 4STAR along the NASA DC-8 flight trajectories matches the south-Korean regional average derived from GOCI. We also observed that, contrary to prevalent understanding, AE and FMF are more spatially variable than AOD during KORUS-AQ, even when accounting for potential sampling biases by using Monte Carlo resampling. Averaging between measurements and model for the entire KORUS-AQ period, a reduction in correlation by 15 % is 65.0 km for AOD and shorter at 22.7 km for AE. While there are observational and model differences, the predominant factor influencing spatial-temporal homogeneity is the meteorological period. High spatio-temporal variability occur during the dynamic period (25–31 May), and low spatio-temporal variability occur during blocking Rex pattern (01–07 June). The changes in spatial variability scales between AOD and FMF/AE, while inter-related, indicate that microphysical processes that impact mostly the dominant aerosol size, like aerosol particle formation, growth, and coagulation, vary at shorter scales than the aerosol concentration processes that mostly impact AOD, like aerosol emission, transport, and removal.

scholarly journals Estimating ground-level PM<sub>2.5</sub> in Eastern China using aerosol optical depth determined from the GOCI Satellite Instrument

2015 ◽  
Vol 15 (12) ◽  
pp. 17251-17281 ◽  
Author(s):  
J. Xu ◽  
R. V. Martin ◽  
A. van Donkelaar ◽  
J. Kim ◽  
M. Choi ◽  
...  
Keyword(s):  
Organic Matter ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Transport Model ◽  
Eastern China ◽  
Ground Level ◽  
East China ◽  
Chemical Transport Model ◽  
Near Surface ◽  
Significant Agreement

Abstract. We determine and interpret fine particulate matter (PM2.5) concentrations in East China for January to December 2013 at a horizontal resolution of 6 km from aerosol optical depth (AOD) retrieved from the Korean Geostationary Ocean Color Imager (GOCI) satellite instrument. We implement a set of filters to minimize cloud contamination in GOCI AOD. Evaluation of filtered GOCI AOD with AOD from the Aerosol Robotic Network (AERONET) indicates significant agreement with mean fractional bias (MFB) in Beijing of 6.7 % and northern Taiwan of −1.2 %. We use a global chemical transport model (GEOS-Chem) to relate the total column AOD to the near-surface PM2.5. The simulated PM2.5/AOD ratio exhibits high consistency with ground-based measurements (MFB = −0.52–8.0 %). We evaluate the satellite-derived PM2.5 vs. the ground-level PM2.5 in 2013 measured by the China Environmental Monitoring Center. Significant agreement is found between GOCI-derived PM2.5 and in-situ observations in both annual averages (r = 0.81, N = 494) and monthly averages (MFB = 13.1 %), indicating GOCI provides valuable data for air quality studies in Northeast Asia. The GEOS-Chem simulated chemical speciation of GOCI-derived PM2.5 reveals that secondary inorganics (SO42−, NO3−, NH4+) and organic matter are the most significant components. Biofuel emissions in northern China for heating are responsible for an increase in the concentration of organic matter in winter. The population-weighted GOCI-derived PM2.5 over East China for 2013 is 53.8 μg m−3, threatening the health and life expectancy of its 600 million residents.

scholarly journals Estimated total emissions of trace gases from the Canberra wildfires of 2003: a new method using satellite measurements of aerosol optical depth and the MOZART chemical transport model

2010 ◽  
Vol 10 (1) ◽  
pp. 977-1004
Author(s):  
C. Paton-Walsh ◽  
L. K. Emmons ◽  
S. R. Wilson
Keyword(s):  
Carbon Monoxide ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Transport Model ◽  
Trace Gases ◽  
Chemical Transport ◽  
New Method ◽  
Chemical Transport Model ◽  
Additional Tool ◽  
Vegetation Fires

Abstract. In this paper we describe a new method for estimating trace gas emissions from large vegetation fires using measurements of aerosol optical depth from the MODIS instruments onboard NASA's Terra and Aqua satellites, combined with the atmospheric chemical transport model MOZART. The model allows for an estimate of double counting of enhanced levels of aerosol optical depth in consecutive satellite overpasses. Using this method we infer an estimated total emission of 10±3 Tg of carbon monoxide from the Canberra fires of 2003. Emissions estimates for several other trace gases are also given. An assessment of the uncertainties in the new method is made and we show that our estimate agrees (within expected uncertainties) with estimates made using current conventional methods of multiplying together factors for the area burned, fuel load, the combustion efficiency and the emission factor for carbon monoxide. The new method for estimating emissions from large vegetation fires described in this paper has some significant uncertainties, but these are mainly quantifiable and largely independent of the uncertainties inherent in conventional techniques. Thus we conclude that the new method is a useful additional tool for characterising emissions from vegetation fires.

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