scholarly journals Seasonal Variability of Atmospheric Aerosols in Karachi, Pakistan

2019 ◽  
Vol 10 (1) ◽  
pp. 57-63
Author(s):  
Badar Ghauri ◽  
Zahid Khalil ◽  
Muhammad Shafiq ◽  
Hussain Haider Rizvi ◽  
Jawad Nasir ◽  
...  
Keyword(s):  
Black Carbon ◽  
Optical Depth ◽  
Atmospheric Aerosols ◽  
One Year ◽  
The City ◽  
Derived Data ◽  
Carbon Concentrations ◽  
Aerosol Type

A variety of in situ and satellite-derived data of aerosols like atmospheric black carbon concentrations wereused to probe the seasonal differences of aerosol concentration in Karachi, Pakistan for one year. Daily [black carbon]varied from about 4000 to 50,000 ng/m3 with the mean maximum of 14700 ng/m3 in February, primarily duringmornings and evenings. The [black carbon] concentrations were at a maximum during winter months of November toFebruary i.e. around 12000 ng/m3 and were at minimum value during summer from June to September (3000 ng/m3).Short term and long-term variabilities were mostly affected by meteorological parameters. Apart from industrial andindiscriminate solid waste burning, most important source of BC emissions in Karachi was vehicular traffic, since overa million vehicles were registered in the city. Aerosol Optical Depth (AOD) from multi-band AOD, AERONET, andMODIS satellites showed a similar trend of its concentrations similar to BC. Aeronet 500 nm AODs were at amaximum for July (0.95 monsoons) and minimum (around 0.4) in November-February. Seasonal variation of AOD(Aeronet) was matching at other wavelengths, while the deviation in the spectral dependency of AOD was uncertain. Itimplied that a columnar spectral optical depth represented different aerosol type association having advection fromvarious directions and sources. Relevant stakeholders should play their role to reduce BC emissions to mitigate illhealth impacts in this metropolitan city.

scholarly journals Seasonal Variability of Atmospheric Aerosols in Karachi, Pakistan

2019 ◽  
Vol 10 (1) ◽  
pp. 57-63
Author(s):  
Badar Ghauri ◽  
Zahid Khalil ◽  
Muhammad Shafiq ◽  
Hussain Haider Rizvi ◽  
Jawad Nasir ◽  
...  
Keyword(s):  
Black Carbon ◽  
Optical Depth ◽  
Atmospheric Aerosols ◽  
One Year ◽  
The City ◽  
Derived Data ◽  
Carbon Concentrations ◽  
Aerosol Type

A variety of in situ and satellite-derived data of aerosols like atmospheric black carbon concentrations wereused to probe the seasonal differences of aerosol concentration in Karachi, Pakistan for one year. Daily [black carbon]varied from about 4000 to 50,000 ng/m3 with the mean maximum of 14700 ng/m3 in February, primarily duringmornings and evenings. The [black carbon] concentrations were at a maximum during winter months of November toFebruary i.e. around 12000 ng/m3 and were at minimum value during summer from June to September (3000 ng/m3).Short term and long-term variabilities were mostly affected by meteorological parameters. Apart from industrial andindiscriminate solid waste burning, most important source of BC emissions in Karachi was vehicular traffic, since overa million vehicles were registered in the city. Aerosol Optical Depth (AOD) from multi-band AOD, AERONET, andMODIS satellites showed a similar trend of its concentrations similar to BC. Aeronet 500 nm AODs were at amaximum for July (0.95 monsoons) and minimum (around 0.4) in November-February. Seasonal variation of AOD(Aeronet) was matching at other wavelengths, while the deviation in the spectral dependency of AOD was uncertain. Itimplied that a columnar spectral optical depth represented different aerosol type association having advection fromvarious directions and sources. Relevant stakeholders should play their role to reduce BC emissions to mitigate illhealth impacts in this metropolitan city.

scholarly journals Nine years of UV aerosol optical depth measurements at Thessaloniki, Greece

2007 ◽  
Vol 7 (8) ◽  
pp. 2091-2101 ◽  
Author(s):  
S. Kazadzis ◽  
A. Bais ◽  
V. Amiridis ◽  
D. Balis ◽  
C. Meleti ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Back Trajectories ◽  
Air Masses ◽  
North Eastern ◽  
Range Transport ◽  
Air Quality Monitoring Stations ◽  
Pm 10 ◽  
The City

Abstract. Spectral measurements of the aerosol optical depth (AOD) and the Ångström coefficient were conducted at Thessaloniki, Greece (40.5° N, 22.9° E) between January 1997 and December 2005 with a Brewer MKIII double-monochromator spectroradiometer. The dataset was compared with collocated measurements of a second spectroradiometer (Brewer MKII) and a CIMEL sun-photometer, showing correlations of 0.93 and 0.98, respectively. A seasonal variation of the AOD was observed at Thessaloniki, with AOD values at 340 nm of 0.52 and 0.28 for August and December respectively. Back trajectories of air masses for up to 4 days were used to assess the influence of long-range transport from various regions to the aerosol load over Thessaloniki. It is shown that part of the observed seasonality can be attributed to air masses with high AOD originating from North-Eastern and Eastern directions during summertime. The analysis of the long-term record (9 years) of AOD showed a downward tendency. A similar decreasing tendency was found in the record of the PM$_{10}$ aerosol measurements, which are conducted near the surface at 4 air-quality monitoring stations in the area of the city of Thessaloniki.

scholarly journals A characterization of Arctic aerosols on the basis of aerosol optical depth and black carbon measurements

Elem Sci Anth ◽  
2014 ◽  
Vol 2 ◽  
Author(s):  
R. S. Stone ◽  
S. Sharma ◽  
A. Herber ◽  
K. Eleftheriadis ◽  
D. W. Nelson
Keyword(s):  
Black Carbon ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Atmospheric Aerosols ◽  
Surface Radiation ◽  
Radiation Budget ◽  
The Arctic ◽  
Carbonaceous Particles ◽  
Surface Warming ◽  
Soot Deposition

Abstract Aerosols, transported from distant source regions, influence the Arctic surface radiation budget. When deposited on snow and ice, carbonaceous particles can reduce the surface albedo, which accelerates melting, leading to a temperature-albedo feedback that amplifies Arctic warming. Black carbon (BC), in particular, has been implicated as a major warming agent at high latitudes. BC and co-emitted aerosols in the atmosphere, however, attenuate sunlight and radiatively cool the surface. Warming by soot deposition and cooling by atmospheric aerosols are referred to as “darkening” and “dimming” effects, respectively. In this study, climatologies of spectral aerosol optical depth AOD (2001–2011) and Equivalent BC (EBC) (1989–2011) from three Arctic observatories and from a number of aircraft campaigns are used to characterize Arctic aerosols. Since the 1980s, concentrations of BC in the Arctic have decreased by more than 50% at ground stations where in situ observations are made. AOD has increased slightly during the past decade, with variations attributed to changing emission inventories and source strengths of natural aerosols, including biomass smoke and volcanic aerosol, further influenced by deposition rates and airflow patterns.

scholarly journals Monitoring atmospheric particulate matters using vertically resolved measurements of a polarization lidar, in-situ recordings and satellite data over Tehran, Iran

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Hossein Panahifar ◽  
Ruhollah Moradhaseli ◽  
Hamid Reza Khalesifard
Keyword(s):  
Boundary Layer ◽  
Atmospheric Aerosols ◽  
Urban Pollution ◽  
Ground Level ◽  
Dust Particles ◽  
Depolarization Ratio ◽  
Backscatter Coefficient ◽  
Dust Events ◽  
The City

AbstractThe highly polluted atmosphere above Tehran has been investigated by using a polarization lidar operating at 532 nm, in-situ particulate matter suites distributed over the city, and meteorological observations. The measurement campaign is conducted from Nov. 2014 to Jan. 2016. Three typical cases are studied in detail where, the atmosphere is polluted with urban pollution, mixture of urban pollution and dust particles from local sources, and long range transported dust from the Arabian Peninsula. For these cases, vertical profiles of the lidar backscatter coefficient, extinction coefficients, particle depolarization ratio ($$\delta _{\text {p}}$$ δ p ) and mass concentrations of atmospheric aerosols (separated into dust and non-dust particles) are presented. Using the lidar recordings, variations of the planetary boundary layer height above the city are investigated along the year. During November to February, lidar profiles frequently show polluted boundary layers that are reaching up to 1 km above the ground level. The depolarization ratio ($$\delta _{\text {p}}$$ δ p ) varies between 0.04 and 0.08 in the polluted boundary layer. During the campaign, for 103 days the urban pollution was dominant, 45 recorded dust events ($$0.15<\delta _{\text {p}}<0.20$$ 0.15 < δ p < 0.20 ) were originated from the dry regions in the south of Tehran and 15 dust events ($$0.20<\delta _{\text {p}}<0.35$$ 0.20 < δ p < 0.35 ) impacted the city that were originated from the Arabian Desert and Mesopotamia.

Constraining direct aerosol radiative forcing using remote sensing and in-situ constraints

2020 ◽  
Author(s):  
Lucia Timea Deaconu ◽  
Duncan Watson-Parris ◽  
Philip Stier ◽  
Lindsay Lee
Keyword(s):  
Remote Sensing ◽  
Black Carbon ◽  
Optical Depth ◽  
Radiative Forcing ◽  
Removal Rates ◽  
Aerosol Radiative Forcing ◽  
Aerosol Absorption ◽  
Direct Radiative Forcing ◽  
Aerosol Radiative

&lt;p&gt;Absorbing aerosols affect the climate system (radiative forcing, cloud formation, precipitation and more) by strongly absorbing solar radiation, particularly at ultraviolet and visible wavelengths. The environmental impacts of an absorbing aerosol layer are influenced by its single scattering albedo (SSA), the albedo of the underlying surface, and also by the atmospheric residence time and column concentration of the aerosols.&lt;/p&gt;&lt;p&gt;Black-carbon (BC), the collective term used for strongly absorbing, carbonaceous aerosols, emitted by incomplete combustion of fossil fuel, biofuel and biomass, is a significant contributor to atmospheric absorption and probably a main-driver in inter-model differences and large uncertainties in estimating the aerosol radiative forcing due to aerosol-radiation interaction (RFari). Estimates of BC direct radiative forcing suggest a positive effect of +0.71 Wm&lt;sup&gt;-2&lt;/sup&gt; (Bond and Bergstrom (2006)) with large uncertainties [+0.08, +1.27] Wm&lt;sup&gt;-2&lt;/sup&gt;. These uncertainties result from poor estimates of BC atmospheric burden (emissions and removal rates) and its radiative properties. The uncertainty in the burden is due to the uncertainty in emissions (7.5 [2, 29] Tg yr&lt;sup&gt;-1&lt;/sup&gt;) and lifetime (removal rates). In comparison with the available observations, global climate models (GCMs) tend to under-predict absorption near source (e.g. at AERONET stations), and over-predict concentrations in remote regions (e.g. as measured by aircraft campaigns). This may be due to GCM&amp;#8217;s weak emissions at the source, but longer lifetime of aerosols in the atmosphere.&lt;/p&gt;&lt;p&gt;This study aims to address the parametric uncertainty of GCMs and constrain the direct radiative forcing using a perturbed parameter ensemble (PPE) and a collection of observations, from remote sensing to in-situ measurements. Total atmospheric aerosol extinction is quantified using satellite observations that provide aerosol optical depth (AOD), while the SSA is constrained by the use of high-temporal resolution aerosol absorption optical depth (AAOD) measured with AERONET sun-photometers (for near-source columnar information of aerosol absorption) and airborne black-carbon in-situ measurements collected and synthesised in the Global Aerosol Synthesis and Science Project (GASSP) (for properties of long-range transported aerosols). Measurements from the airborne campaigns ATOM and HIPPO are valuable for constraining aerosol absorption in remote areas, while CLARIFY and ORACLES, that were employed over Southeast Atlantic, are considered in our study for near source observations of biomass burning aerosols transported over the bright surface of stratocumulus clouds.&lt;/p&gt;&lt;p&gt;Using the PPE to explore the uncertainties in the aerosol absorption as well as the dominant emission and removal processes, and by comparing with a variety of observations we have confidence to better constrain the aerosol direct radiative forcing.&lt;/p&gt;

scholarly journals Comparison of the optical depth of total ozone and atmospheric aerosols in Poprad-Gánovce, Slovakia

2017 ◽  
Author(s):  
Peter Hrabčák
Keyword(s):  
Ultraviolet Radiation ◽  
Optical Depth ◽  
Satellite Data ◽  
Atmospheric Aerosols ◽  
Total Ozone ◽  
Solar Spectrum ◽  
Atmospheric Ozone ◽  
Satellite Measurements ◽  
Two Factors

Abstract. Atmospheric ozone along with aerosols significantly affect the amount of ultraviolet solar radiation that reaches on the Earth's surface. Presented study is focused on the comparison of the optical depth of total ozone and atmospheric aerosols in the area of Poprad-Gánovce situated at the altitude of 706 meters above sea level, close to the highest peak of the Carpathian Mountains. Measurements of direct sun ultraviolet radiation are carried out here continuously since 1994 using the Brewer Ozone Spectrophotometer type MK IV. These measurements are used to calculate the total amount of atmospheric ozone and consequently its optical depth. Measurements can also be used to determine the optical depth of atmospheric aerosols using the Langley plot method. In this study, those two factors causing a significant reduction in the direct sun ultraviolet radiation to the Earth's surface are compared to each other. The study is showing results of measurements over 23 years, since 1994 to 2016. Values of optical depth are determined for wavelengths 306.3 nm, 310.1 nm, 313.5 nm, 316.8 nm and 320.1 nm. A statistically significant decrease in the total optical depth of the atmosphere was observed for all investigated wavelengths. Its main cause is the decrease of optical depth of aerosols. The study also presents comparison of the terrestrial and satellite data of total ozone and AOD. A very good match of satellite and terrestrial direct sun measurements of total ozone was found. The use of zenith sky measurements in combination with the direct sun measurements leads to the systematically higher values of total ozone. Comparison of the satellite and terrestrial AOD measurements in the UV range of the solar spectrum is mainly limited by the very low number of days for which AOD can be determined for satellite measurements. It has been found that AOD satellite data is higher than terrestrial in the long-term average.

scholarly journals Long-Term Variation of Black Carbon Absorption Aerosol Optical Depth from AERONET Data over East Asia

2020 ◽  
Vol 12 (21) ◽  
pp. 3551
Author(s):  
Naghmeh Dehkhoda ◽  
Youngmin Noh ◽  
Sohee Joo
Keyword(s):  
East Asia ◽  
Black Carbon ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Anthropogenic Pollution ◽  
Single Scattering ◽  
Chinese Government ◽  
Rapid Reduction ◽  
Term Data

Absorption aerosol optical depth induced by black carbon (AAODBC) was retrieved using the depolarization ratio and single scattering albedo provided by the Aerosol Robotic Network (AERONET) inversion products over East Asia. Our analysis considered AERONET data from six sites in East Asia that are mostly affected by anthropogenic pollution, black carbon (BC) emissions, and natural mineral dust, during the period 2001–2018. We identified a rapid reduction in total aerosol optical depth (AODT) of −0.0106 yr−1 over Beijing, whereas no considerable trend was observed at the Korean and Japanese sites. The long-term data for AAODBC showed decreasing trends at all sites. We conclude that successful emission control policies were the major underlying driver of AODT and AAODBC reductions over East Asia, particularly in China, during the study period. Values of the AAODBC/AODT ratio revealed that, although these policies were successful, the Chinese government needs to undertake stricter measures toward reducing BC emissions. We found that AAODBC follows seasonal trends, peaking in the colder months. This suggests that in East Asia, particularly in China, domestic coal burning is still of concern.

scholarly journals Retrieval of Desert Dust and Carbonaceous Aerosol Emissions over Africa from POLDER/PARASOL Products Generated by GRASP Algorithm

2018 ◽  
Author(s):  
Cheng Chen ◽  
Oleg Dubovik ◽  
Daven K. Henze ◽  
Tatyana Lapyonak ◽  
Mian Chin ◽  
...  
Keyword(s):  
Optical Depth ◽  
Atmospheric Aerosols ◽  
Carbonaceous Aerosol ◽  
Desert Dust ◽  
Modelling Framework ◽  
Aerosol Absorption ◽  
Modelling Studies ◽  
One Year ◽  
Distribution Composition ◽  
Aerosol Emissions

Abstract. Understanding the role atmospheric aerosols play in the earth-atmosphere system is limited by uncertainties in the knowledge of their distribution, composition and sources. In this paper, we use the GEOS-Chem based inverse modelling framework for retrieving desert dust (DD), black carbon (BC) and organic carbon (OC) aerosol emissions simultaneously from aerosol data retrieved from the polarimetric POLDER/PARASOL Aerosol Optical Depth (AOD) and Aerosol Absorption Optical Depth (AAOD) produced with the GRASP algorithm (hereafter PARASOL/GRASP). First, the inversion framework is validated in a series of numerical tests conducted with synthetic PARASOL-like data. These show that the framework allows for retrieval of the distribution and strength of aerosol emissions. For example, the uncertainty of retrieved daily emissions in error free conditions is bellow 25.8 % for DD, 5.9 % for BC and 26.9 % for OC. In addition, BC refractive index is sensitive to BC emission retrieval, which could produce an additional about 1.8 times differences for total BC emission. The approach is then applied to one-year (December 2007 to November 2008) of data over the African and Arabian Peninsula region using PARASOL/GRASP spectral AOD and AAOD at six wavelengths (443, 490, 565, 670, 865 and 1020 nm). Analysis of the resulting retrieved emissions indicates 1.8 times overestimation of the prior DD online mobilization and entrainment model. For total BC and OC, the retrieved emissions show a significant increase of 209.9–271.8 % in comparison to the prior GEOS-Chem inventory of carbonaceous aerosol emissions. The model posterior simulation with retrieved emissions shows good agreement both with the AOD and AAOD PARASOL/GRASP products used in the inversion. The fidelity of the results is evaluated by comparison of posterior simulations with measurements from AERONET that are completely independent of and more temporally frequent than PARASOL observations. To further test the robustness of our posterior emissions constrained using PARASOL/GRASP, the posterior emissions are implemented in the GEOS-5/GOCART model and the consistency of simulated AOD (prior: R = 0.77, RMSE = 0.14, MAE = 0.09; posterior: R = 0.81, RMSE = 0.10, MAE = 0.06) and AAOD (prior: R = 0.65, RMS = 0.019, MAE = 0.014; posterior: R = 0.69, RMSE = 0.015, MAE = 0.011) with other independent measurements (MODIS and OMI) demonstrates promise in applying this database for modelling studies.

scholarly journals Aerosol Optical Depth and Black Carbon Concentration along the Coast of Bay of Bengal

2020 ◽  
Vol 8 (5) ◽  
pp. 1493-1496
Keyword(s):  
Black Carbon ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Atmospheric Aerosols ◽  
Carbon Concentration ◽  
Bay Of Bengal ◽  
Radiation Monitoring ◽  
Climate Forcing ◽  
Atmospheric Effect ◽  
Black Carbon Concentration

Climate can be affected by Atmospheric Aerosols through the Earths’ incoming solar radiation. Monitoring of aerosol concentrations is essential for understanding the atmospheric effect on the earth’s surface. Therefore, the Aerosol and their radiative effects are important in climate forcing studies. This study is undertaken to investigate the aerosol optical depth and black carbon concentration by satellite based measurements over Bay of Bengal.

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