scholarly journals Natural aerosols explain seasonal and spatial patterns of Southern Ocean cloud albedo

2015 ◽  
Vol 1 (6) ◽  
pp. e1500157 ◽  
Author(s):  
Daniel T. McCoy ◽  
Susannah M. Burrows ◽  
Robert Wood ◽  
Daniel P. Grosvenor ◽  
Scott M. Elliott ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Atmospheric Aerosols ◽  
Suspended Solid ◽  
Spatiotemporal Variability ◽  
Anthropogenic Aerosols ◽  
Spatially Correlated ◽  
Cloud Properties ◽  
Planetary Albedo ◽  
High Concentrations ◽  
Natural Aerosols

Atmospheric aerosols, suspended solid and liquid particles, act as nucleation sites for cloud drop formation, affecting clouds and cloud properties—ultimately influencing the cloud dynamics, lifetime, water path, and areal extent that determine the reflectivity (albedo) of clouds. The concentration Nd of droplets in clouds that influences planetary albedo is sensitive to the availability of aerosol particles on which the droplets form. Natural aerosol concentrations affect not only cloud properties themselves but also modulate the sensitivity of clouds to changes in anthropogenic aerosols. It is shown that modeled natural aerosols, principally marine biogenic primary and secondary aerosol sources, explain more than half of the spatiotemporal variability in satellite-observed Nd. Enhanced Nd is spatially correlated with regions of high chlorophyll a, and the spatiotemporal variability in Nd is found to be driven primarily by high concentrations of sulfate aerosol at lower Southern Ocean latitudes (35o to 45oS) and by organic matter in sea spray aerosol at higher latitudes (45o to 55oS). Biogenic sources are estimated to increase the summertime mean reflected solar radiation in excess of 10 W m–2 over parts of the Southern Ocean, which is comparable to the annual mean increases expected from anthropogenic aerosols over heavily polluted regions of the Northern Hemisphere.

scholarly journals Spatiotemporal variability and contribution of different aerosol types to the aerosol optical depth over the Eastern Mediterranean

2016 ◽  
Vol 16 (21) ◽  
pp. 13853-13884 ◽  
Author(s):  
Aristeidis K. Georgoulias ◽  
Georgia Alexandri ◽  
Konstantinos A. Kourtidis ◽  
Jos Lelieveld ◽  
Prodromos Zanis ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Eastern Mediterranean ◽  
Spatiotemporal Variability ◽  
Marine Aerosols ◽  
Anthropogenic Aerosols ◽  
Relative Contribution ◽  
Fine Mode ◽  
Natural Aerosols ◽  
Aerosol Types

Abstract. This study characterizes the spatiotemporal variability and relative contribution of different types of aerosols to the aerosol optical depth (AOD) over the Eastern Mediterranean as derived from MODIS (Moderate Resolution Imaging Spectroradiometer) Terra (March 2000–December 2012) and Aqua (July 2002–December 2012) satellite instruments. For this purpose, a 0.1° × 0.1° gridded MODIS dataset was compiled and validated against sun photometric observations from the AErosol RObotic NETwork (AERONET). The high spatial resolution and long temporal coverage of the dataset allows for the determination of local hot spots like megacities, medium-sized cities, industrial zones and power plant complexes, seasonal variabilities and decadal averages. The average AOD at 550 nm (AOD550) for the entire region is ∼ 0.22 ± 0.19, with maximum values in summer and seasonal variabilities that can be attributed to precipitation, photochemical production of secondary organic aerosols, transport of pollution and smoke from biomass burning in central and eastern Europe and transport of dust from the Sahara and the Middle East. The MODIS data were analyzed together with data from other satellite sensors, reanalysis projects and a chemistry–aerosol-transport model using an optimized algorithm tailored for the region and capable of estimating the contribution of different aerosol types to the total AOD550. The spatial and temporal variability of anthropogenic, dust and fine-mode natural aerosols over land and anthropogenic, dust and marine aerosols over the sea is examined. The relative contribution of the different aerosol types to the total AOD550 exhibits a low/high seasonal variability over land/sea areas, respectively. Overall, anthropogenic aerosols, dust and fine-mode natural aerosols account for ∼ 51, ∼ 34 and ∼ 15 % of the total AOD550 over land, while, anthropogenic aerosols, dust and marine aerosols account ∼ 40, ∼ 34 and ∼ 26 % of the total AOD550 over the sea, based on MODIS Terra and Aqua observations.

scholarly journals Spatiotemporal variability and contribution of different aerosol types to the Aerosol Optical Depth over the Eastern Mediterranean

2016 ◽  
Author(s):  
Aristeidis K. Georgoulias ◽  
Georgia Alexandri ◽  
Konstantinos A. Kourtidis ◽  
Jos Lelieveld ◽  
Prodromos Zanis ◽  
...  
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Eastern Mediterranean ◽  
Spatiotemporal Variability ◽  
Marine Aerosols ◽  
Anthropogenic Aerosols ◽  
Relative Contribution ◽  
Fine Mode ◽  
Natural Aerosols ◽  
Aerosol Types

Abstract. This study characterizes the spatiotemporal variability and relative contribution of different types of aerosols to the Aerosol Optical Depth (AOD) over the Eastern Mediterranean as derived from MODIS Terra (3/2000–12/2012) and Aqua (7/2002–12/2012) satellite instruments. For this purpose, a 0.1°×0.1° gridded MODIS dataset was compiled and validated against AERONET sunphotometric observations. The high spatial resolution and long temporal coverage of the dataset allows for the determination of local hot spots like megacities, medium sized cities, industrial zones, and power plant complexes, seasonal variabilities, and decadal averages. The average AOD at 550 nm (AOD550) for the entire region is ~ 0.22 ± 0.19 with maximum values in summer and seasonal variabilities that can be attributed to precipitation, photochemical production of secondary organic aerosols, transport of pollution and smoke from biomass burning in Central and Eastern Europe, and transport of dust from the Sahara Desert and the Middle East. The MODIS data were analyzed together with data from other satellite sensors, reanalysis projects and a chemistry-aerosol-transport model using an optimized algorithm tailored for the region and capable of estimating the contribution of different aerosol types to the total AOD550. The spatial and temporal variability of anthropogenic, dust and fine mode natural aerosols over land and anthropogenic, dust and marine aerosols over the sea is examined. The relative contribution of the different aerosol types to the total AOD550 exhibits a low/high seasonal variability over land/oceanic areas, respectively. Overall, anthropogenic aerosols, dust and fine mode natural aerosols account for ~ 51 %, ~ 34 % and ~ 15 % of the total AOD550 over land, while, anthropogenic aerosols, dust and marine aerosols account ~ 40 %, ~ 34 % and ~ 26 % of the total AOD550 over the sea, based on MODIS Terra and Aqua observations.

Biological Mechanisms of H2S Formation in Sewer Pipes

1992 ◽  
Vol 26 (3-4) ◽  
pp. 907-914 ◽  
Author(s):  
A. Attal ◽  
M. Brigodiot ◽  
P. Camacho ◽  
J. Manem
Keyword(s):  
Suspended Solid ◽  
Urban Wastewater ◽  
Biological Mechanisms ◽  
Sewer Pipes ◽  
Sulfate Reducing ◽  
Biological Phenomena ◽  
Low Concentrations ◽  
Production Of Hydrogen ◽  
High Concentrations ◽  
Reducing Bacteria

The purpose of this study is to gain a better understanding of the biological phenomena involved in the production of hydrogen sulfide in urban wastewater (UWW) systems. It is found that the UWW itself naturally possesses the biomass needed to consume the sulfates. These heterotrophic sulfate-reducing bacteria populations, though immediately active in strict anaerobic conditions, are present only in very low concentrations in the UWW. A concentration of them was studied within the pressure pipes, in the form of deposits, and this justifies the high concentrations of sulfides measured in certain wastewater networks. There are two reasons why the ferrous sulfate used as a treatment in any wastewater networks should not cause the production of additional sulfides. Firstly, the sulfate consumption kinetics are always too slow, relative to the residence time of the water in the pipe, for all of the sulfates to be consumed anyway. Secondly, the amount of assimilable carbon, soluble carbon, and carbon from suspended solid (SS) hydrolysis is insufficient.

scholarly journals Development, characterization and first deployment of an improved online reactive oxygen species analyzer

2018 ◽  
Vol 11 (1) ◽  
pp. 65-80 ◽  
Author(s):  
Jun Zhou ◽  
Emily A. Bruns ◽  
Peter Zotter ◽  
Giulia Stefenelli ◽  
André S. H. Prévôt ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Detection Limit ◽  
Atmospheric Aerosols ◽  
Half Life ◽  
Matrix Effects ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Wood Combustion ◽  
Storage Duration ◽  
High Concentrations

Abstract. Inhalation of atmospheric particles is linked to human diseases. Reactive oxygen species (ROS) present in these atmospheric aerosols may play an important role. However, the ROS content in aerosols and their formation pathways are still largely unknown. Here, we have developed an online and offline ROS analyzer using a 2′,7′-dichlorofluorescin (DCFH) based assay. The ROS analyzer was calibrated with H2O2 and its sensitivity was characterized using a suite of model organic compounds. The instrument detection limit determined as 3 times the noise is 1.3 nmol L−1 for offline analysis and 2 nmol m−3 of sampled air when the instrument is operated online at a fluorescence response time of approximately 8 min, while the offline method detection limit is 18 nmol L−1. Potential interferences from gas-phase O3 and NO2 as well as matrix effects of particulate SO42− and NO3− were tested, but not observed. Fe3+ had no influence on the ROS signal, while soluble Fe2+ reduced it if present at high concentrations in the extracts. Both online and offline methods were applied to identify the ROS content of different aerosol types, i.e., ambient aerosols as well as fresh and aged aerosols from wood combustion emissions. The stability of the ROS was assessed by comparing the ROS concentration measured by the same instrumentation online in situ with offline measurements. We also analyzed the evolution of ROS in specific samples by conducting the analysis after storage times of up to 4 months. The ROS were observed to decay with increasing storage duration. From their decay behavior, ROS in secondary organic aerosol (SOA) can be separated into short- and long-lived fractions. The half-life of the short-lived fraction was 1.7 ± 0.4 h, while the half-life of the long-lived fraction could not be determined with our uncertainties. All these measurements showed consistently that on average 60 ± 20 % of the ROS were very reactive and disappeared during the filter storage time. This demonstrates the importance of a fast online measurement of ROS.

Influences of Recent Particle Formation on Southern Ocean Aerosol Variability and Low Cloud Properties

2021 ◽  
Author(s):  
Isabel L. McCoy ◽  
Christopher S. Bretherton ◽  
Robert Wood ◽  
Cynthia H. Twohy ◽  
Andrew Gettelman ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Particle Formation ◽  
Cloud Properties ◽  
Low Cloud

scholarly journals Regional effects of atmospheric aerosols on temperature: an evaluation of an ensemble of online coupled models

2017 ◽  
Vol 17 (15) ◽  
pp. 9677-9696 ◽  
Author(s):  
Rocío Baró ◽  
Laura Palacios-Peña ◽  
Alexander Baklanov ◽  
Alessandra Balzarini ◽  
Dominik Brunner ◽  
...  
Keyword(s):  
Atmospheric Aerosols ◽  
Atmospheric Aerosol ◽  
Correlation Coefficients ◽  
Spatiotemporal Variability ◽  
Coupled Models ◽  
Climate Effect ◽  
Wave Event ◽  
Simulation Results ◽  
Radiative Feedbacks ◽  
Aerosol Radiative

Abstract. The climate effect of atmospheric aerosols is associated with their influence on the radiative budget of the Earth due to the direct aerosol–radiation interactions (ARIs) and indirect effects, resulting from aerosol–cloud–radiation interactions (ACIs). Online coupled meteorology–chemistry models permit the description of these effects on the basis of simulated atmospheric aerosol concentrations, although there is still some uncertainty associated with the use of these models. Thus, the objective of this work is to assess whether the inclusion of atmospheric aerosol radiative feedbacks of an ensemble of online coupled models improves the simulation results for maximum, mean and minimum temperature at 2 m over Europe. The evaluated models outputs originate from EuMetChem COST Action ES1004 simulations for Europe, differing in the inclusion (or omission) of ARI and ACI in the various models. The cases studies cover two important atmospheric aerosol episodes over Europe in the year 2010: (i) a heat wave event and a forest fire episode (July–August 2010) and (ii) a more humid episode including a Saharan desert dust outbreak in October 2010. The simulation results are evaluated against observational data from the E-OBS gridded database. The results indicate that, although there is only a slight improvement in the bias of the simulation results when including the radiative feedbacks, the spatiotemporal variability and correlation coefficients are improved for the cases under study when atmospheric aerosol radiative effects are included.

Influences of Recent Particle Formation on Southern Ocean Aerosol Variability and Low Cloud Properties

2021 ◽  
Author(s):  
Isabel L. McCoy ◽  
Christopher S. Bretherton ◽  
Robert Wood ◽  
Cynthia H. Twohy ◽  
Andrew Gettelman ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Particle Formation ◽  
Cloud Properties ◽  
Low Cloud

scholarly journals Characteristics, seasonality and sources of carbonaceous and ionic components in the tropical Indian aerosols

2011 ◽  
Vol 11 (2) ◽  
pp. 3937-3976 ◽  
Author(s):  
C. M. Pavuluri ◽  
K. Kawamura ◽  
S. G. Aggarwal ◽  
T. Swaminathan
Keyword(s):  
Organic Carbon ◽  
Atmospheric Aerosols ◽  
Atmospheric Transport ◽  
Indian Subcontinent ◽  
Ionic Species ◽  
Water Soluble ◽  
Carbonaceous Aerosols ◽  
Mass Fractions ◽  
High Concentrations ◽  
Ionic Components

Abstract. To better characterize South and Southeast Asian aerosols, PM10 samples collected from tropical Chennai, India (13.04° N; 80.17° E) were analyzed for carbonaceous and water-soluble ionic components. Concentration ranges of elemental carbon (EC) and organic carbon (OC) were 2.4–14 μg m−3 and 3.2–15.6 μg m−3 in winter samples whereas they were 1.1–2.5 μg m−3 and 4.1–17.6 μg m−3 in summer samples, respectively. Concentration of secondary organic carbon (SOC) retrieved from EC-tracer method was 4.6 ± 2.8 μg m−3 in winter and 4.3 ± 2.8 μg m−3 in summer. SO42- (8.8 ± 2.5 μg m−3 and 4.1 ± 2.7 μg m−3 in winter and summer, respectively) was found as the most abundant ionic species (57% on average, n = 49), followed by NH4+ (15%) > NO3− > Cl− > K+> Na+ > Ca2+ > MSA− > Mg2+. The mass fractions of EC, organic matter (OM) and ionic species varied seasonally, following the air mass trajectories and corresponding source strength. Based on mass concentration ratios of selected components and relations of EC and OC to marker species, we found that biofuel/biomass burning is the major source of atmospheric aerosols in South and Southeast Asia. The high concentrations of SOC and WSOC/OC ratios (ave. 0.45; n = 49) as well as good correlations between SOC and WSOC suggest that the secondary production of organic aerosols during long-range atmospheric transport is also significant in this region. This study provides the baseline data of carbonaceous aerosols for southern part of the Indian subcontinent.

Cloudiness and Earth's hemispheric albedo symmetry

2021 ◽  
Author(s):  
George Datseris ◽  
Bjorn Stevens
Keyword(s):  
Surface Albedo ◽  
Shortwave Radiation ◽  
Cloud Albedo ◽  
Radiation Data ◽  
Cloud Properties ◽  
Open Questions ◽  
Long Time ◽  
Planetary Albedo ◽  
Hemispheric Communication ◽  
Radiation Measurements

<p>Radiation measurements at the top of the atmosphere show that the two hemispheres of Earth reflect the same amount of shortwave radiation in the long time average (so-called hemispheric albedo symmetry). Here we try to find the origin of this symmetry by analyzing radiation data directly, as well as cloud properties. The radiation data, while being mostly noise, hint that a hemispheric communication mechanism is likely but do not provide enough information to identify it. Cloud properties allow us to define an effective cloud albedo field, much more useful than the commonly used cloud area fraction. Based on that we first show that extra cloud albedo of the SH exactly compensates the extra surface albedo of the NH. We then identify that this this compensation comes almost exclusively from the storm tracks of the extratropics. We close discussing the importance of approaching planetary albedo as a whole and open questions that remain.</p>

The Long Term Spatial-temporal Distribution of Aerosol Optical Depth and Its Associated Atmospheric Circulation Over Southeast Africa.

2021 ◽  
Author(s):  
Matthews Nyasulu ◽  
Md. Mozammel Haque ◽  
Bathsheba Musonda ◽  
Cao Fang
Keyword(s):  
Human Health ◽  
Atmospheric Circulation ◽  
Atmospheric Aerosols ◽  
Crop Residues ◽  
Temporal Distribution ◽  
Western Coast ◽  
High Concentration ◽  
Anthropogenic Aerosols ◽  
Anthropogenic Aerosol

Abstract Recent studies have revealed significant impacts of increased concentration of anthropogenic aerosols in the atmosphere to both climate and human health. Southeast Africa is one of the regions where studies related to atmospheric aerosols remain scant, causing high uncertainty in predicting and understanding the impacts of these aerosols to both climate and human health. The present study therefore has investigated the long term spatial-temporal distribution of atmospheric aerosols, trends, its relationship with cloud properties and the associated atmospheric circulation over the region. High concentration of aerosol has been detected during the dry months of September to November (SON) while low during March to May (MAM) and June-July (JJA) seasons in most areas. Highest 550 was recorded in areas with low elevation such as over Lake Malawi, Zambezi valley and along the western coast of the Indian Ocean. The average of the detected concentration is however low as compared to highly polluted regions of the globe. Statistical analyses revealed insignificant change of AOD550 in most areas between 2002 and 2020 time period. The study has also revealed seasonality of aerosol distribution highly influenced by changes in atmospheric circulation. Burning of biomass during dry months such bush fires and burning of crop residues remain the major source of anthropogenic aerosol concentration over Southeast Africa hence needs to be controlled.

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