scholarly journals Long-term trends in aerosol optical characteristics in the Po Valley, Italy

2014 ◽  
Vol 14 (17) ◽  
pp. 9129-9136 ◽  
Author(s):  
J. P. Putaud ◽  
F. Cavalli ◽  
S. Martins dos Santos ◽  
A. Dell'Acqua
Keyword(s):  
Radiative Forcing ◽  
Mass Concentration ◽  
Measurement Data ◽  
Single Scattering ◽  
Po Valley ◽  
Aerosol Absorption ◽  
Aerosol Scattering ◽  
Sun Photometer ◽  
The One

Abstract. Aerosol properties have been monitored by ground-based in situ and remote sensing measurements at the station for atmospheric research located in Ispra, on the edge of the Po Valley, for almost one decade. In situ measurements are performed according to Global Atmosphere Watch recommendations, and quality is assured through the participation in regular inter-laboratory comparisons. Sun-photometer data are produced by the Aerosol Robotic Network (AERONET). Data show significant decreasing trends over the 2004–2010 period for a number of variables, including particulate matter (PM) mass concentration, aerosol scattering, backscattering and absorption coefficients, and aerosol optical thickness (AOT). In situ measurement data show no significant trends in the aerosol backscatter ratio, but they do show a significant decreasing trend of about −0.7 ± 0.3% yr−1 in the aerosol single scattering albedo (SSA) in the visible light range. Similar trends are observed in the SSA retrieved from sun-photometer measurements. Correlations appear between in situ PM mass concentration and aerosol scattering coefficient, on the one hand, and elemental carbon (EC) concentration and aerosol absorption coefficient, on the other hand. However, no increase in the EC / PM ratio was observed, which could have explained the decrease in SSA. The application of a simple approximation to calculate the direct radiative forcing by aerosols suggests a significant diminution in their cooling effect, mainly due to the decrease in AOT. Applying the methodology we present to those sites, where the necessary suite of measurements is available, would provide important information to inform future policies for air-quality enhancement and fast climate change mitigation.

scholarly journals Long term trends in aerosol optical characteristics in the Po Valley (IT)

2014 ◽  
Vol 14 (7) ◽  
pp. 9041-9065
Author(s):  
J. P. Putaud ◽  
F. Cavalli ◽  
S. Martins dos Santos ◽  
A. Dell'Acqua
Keyword(s):  
Radiative Forcing ◽  
Mass Concentration ◽  
Measurement Data ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Po Valley ◽  
Aerosol Absorption ◽  
Aerosol Scattering ◽  
The One

Abstract. Aerosols properties have been monitored by ground-based in situ and remote sensing measurements at the station for atmospheric research located in Ispra on the edge of the Po Valley for almost one decade. In-situ measurements are performed according to Global Atmosphere Watch recommendations, and quality is assured through the participation in regular inter-laboratory comparisons. Sunphotometer data are produced by AERONET. Data show significant decreasing trends over 2004–2010 for a number of variables including particulate matter (PM) mass concentration, aerosol scattering, backscattering and absorption coefficients, and aerosol optical thickness (AOT). In-situ measurement data show no significant trend in the aerosol backscatter ratio, but a significant decreasing trend of about −0.7 ± 0.3% in the aerosol single scattering albedo in the visible light range. Similar trends are observed in the aerosol single scattering albedo retrieved from sunphotometer measurements. Correlations appear between in situ PM mass concentration and aerosol scattering coefficient on the one hand, and elemental carbon (EC) and aerosol absorption coefficient on the other hand, however, no increase in the EC / PM ratio was observed, which could have explained the decrease in SSA. The application of a simple approximation to calculate the direct radiative forcing by aerosols suggests a significant diminution in their cooling effect, mainly due to the decrease in AOT. Applying the methodology we present to those sites where the necessary suite of measurements is available would provide important information to inform future policies for air quality enhancement and fast climate change mitigation.

scholarly journals Vertical profiles of sub-micron aerosol single scattering albedo over Indian region immediately before monsoon onset and during its development: Research from the SWAAMI field campaign

2019 ◽  
Author(s):  
Mohanan R. Manoj ◽  
Sreedharan K. Satheesh ◽  
Krishnaswamy K. Moorthy ◽  
Hugh Coe
Keyword(s):  
Active Phase ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Development Research ◽  
Aerosol Absorption ◽  
South West ◽  
Aerosol Scattering ◽  
First Time ◽  
Geographical Locations

Abstract. Vertical structures of aerosol single scattering albedo (SSA), from near the surface through the free troposphere, have been estimated for the first time at distinct geographical locations over the Indian mainland and adjoining oceans, using in-situ measurements of aerosol scattering and absorption coefficients aboard the FAAM BAe-146 aircraft during the South West Asian Aerosol Monsoon Interactions (SWAAMI) campaign from June to July 2016. These are used to examine the spatial variation of SSA profiles and also to characterize its transformation from just prior to the onset of Indian Summer Monsoon (June 2016) to its active phase (July 2016). Very strong aerosol absorption, with SSA values as low as 0.7, persisted in the lower altitudes (

scholarly journals Seasonal differences in the vertical profiles of aerosol optical properties over rural Oklahoma

2011 ◽  
Vol 11 (20) ◽  
pp. 10661-10676 ◽  
Author(s):  
E. Andrews ◽  
P. J. Sheridan ◽  
J. A. Ogren
Keyword(s):  
Seasonal Variability ◽  
Gulf Coast ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Ambient Conditions ◽  
Seasonal Differences ◽  
Aerosol Loading ◽  
Aerosol Absorption ◽  
Aerosol Scattering

Abstract. A small airplane made 597 aerosol optical property (light absorption and light scattering) vertical profile measurements over a rural Oklahoma site between March 2000 and December 2007. The aerosol profiles obtained during these 8 yr of measurements suggest significant seasonal differences in aerosol loading (scattering and absorption). The highest amounts of scattering and absorbing aerosol are observed during the summer and the lowest loading occurs during the winter. The relative contribution of aerosol absorption is highest in the winter (i.e., single scattering albedo is lowest in winter), particularly aloft. Aerosol absorption generally decreased with altitude below ~1.5 km and then was relatively constant or decreased more gradually above that. Aerosol scattering decreased sharply with altitude below ~1.5 km but, unlike absorption, also decreased at higher altitudes, albeit less sharply. Scattering Ångström exponents suggest that the aerosol was dominated by sub-micron aerosol during the summer at all altitudes, but that larger particles were present, especially in the spring and winter above 1 km. The seasonal variability observed for aerosol loading is consistent with AERONET aerosol optical depth (AOD) although the AOD values calculated from in situ adjusted to ambient conditions and matching wavelengths are up to a factor of two lower than AERONET AOD values depending on season. The column averaged single scattering albedo derived from in situ airplane measurements are similar in value to the AERONET single scattering albedo inversion product but the seasonal patterns are different – possibly a consequence of the strict constraints on obtaining single scattering albedo from AERONET data. A comparison of extinction Ångström exponent and asymmetry parameter from the airplane and AERONET platforms suggests similar seasonal variability with smaller particles observed in the summer and fall and larger particles observed in spring and winter. The observed seasonal cycle of aerosol loading corresponds with changes in air mass back trajectories: the aerosol scattering was higher when transport was from polluted areas (e.g., the Gulf Coast) and lower when the air came from cleaner regions and/or the upper atmosphere.

scholarly journals Aerosol absorption profiling from the synergy of lidar and sun-photometry: the ACTRIS-2 campaigns in Germany, Greece and Cyprus

2018 ◽  
Vol 176 ◽  
pp. 08005 ◽  
Author(s):  
Alexandra Tsekeri ◽  
Vassilis Amiridis ◽  
Anton Lopatin ◽  
Eleni Marinou ◽  
Eleni Giannakaki ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Radiative Transfer ◽  
Absorption Coefficient ◽  
Single Scattering ◽  
In Situ Measurements ◽  
Climate Modelling ◽  
Aerosol Absorption ◽  
Sun Photometer ◽  
Remote Sensing Techniques

Aerosol absorption profiling is crucial for radiative transfer calculations and climate modelling. Here, we utilize the synergy of lidar with sun-photometer measurements to derive the absorption coefficient and single scattering albedo profiles during the ACTRIS-2 campaigns held in Germany, Greece and Cyprus. The remote sensing techniques are compared with in situ measurements in order to harmonize and validate the different methodologies and reduce the absorption profiling uncertainties.

scholarly journals Evaluating model parameterizations of submicron aerosol scattering and absorption with in situ data from ARCTAS 2008

2016 ◽  
Vol 16 (14) ◽  
pp. 9435-9455 ◽  
Author(s):  
Matthew J. Alvarado ◽  
Chantelle R. Lonsdale ◽  
Helen L. Macintyre ◽  
Huisheng Bian ◽  
Mian Chin ◽  
...  
Keyword(s):  
Optical Properties ◽  
Size Distribution ◽  
Aerosol Size Distribution ◽  
Visible Radiation ◽  
Submicron Aerosol ◽  
In Situ Data ◽  
Aerosol Absorption ◽  
Aerosol Scattering ◽  
The Impact

Abstract. Accurate modeling of the scattering and absorption of ultraviolet and visible radiation by aerosols is essential for accurate simulations of atmospheric chemistry and climate. Closure studies using in situ measurements of aerosol scattering and absorption can be used to evaluate and improve models of aerosol optical properties without interference from model errors in aerosol emissions, transport, chemistry, or deposition rates. Here we evaluate the ability of four externally mixed, fixed size distribution parameterizations used in global models to simulate submicron aerosol scattering and absorption at three wavelengths using in situ data gathered during the 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. The four models are the NASA Global Modeling Initiative (GMI) Combo model, GEOS-Chem v9-02, the baseline configuration of a version of GEOS-Chem with online radiative transfer calculations (called GC-RT), and the Optical Properties of Aerosol and Clouds (OPAC v3.1) package. We also use the ARCTAS data to perform the first evaluation of the ability of the Aerosol Simulation Program (ASP v2.1) to simulate submicron aerosol scattering and absorption when in situ data on the aerosol size distribution are used, and examine the impact of different mixing rules for black carbon (BC) on the results. We find that the GMI model tends to overestimate submicron scattering and absorption at shorter wavelengths by 10–23 %, and that GMI has smaller absolute mean biases for submicron absorption than OPAC v3.1, GEOS-Chem v9-02, or GC-RT. However, the changes to the density and refractive index of BC in GC-RT improve the simulation of submicron aerosol absorption at all wavelengths relative to GEOS-Chem v9-02. Adding a variable size distribution, as in ASP v2.1, improves model performance for scattering but not for absorption, likely due to the assumption in ASP v2.1 that BC is present at a constant mass fraction throughout the aerosol size distribution. Using a core-shell mixing rule in ASP overestimates aerosol absorption, especially for the fresh biomass burning aerosol measured in ARCTAS-B, suggesting the need for modeling the time-varying mixing states of aerosols in future versions of ASP.

scholarly journals Intercomparison of biomass burning aerosol optical properties from in situ and remote-sensing instruments in ORACLES-2016

2019 ◽  
Vol 19 (14) ◽  
pp. 9181-9208 ◽  
Author(s):  
Kristina Pistone ◽  
Jens Redemann ◽  
Sarah Doherty ◽  
Paquita Zuidema ◽  
Sharon Burton ◽  
...  
Keyword(s):  
Optical Properties ◽  
Case Studies ◽  
Biomass Burning ◽  
Radiative Forcing ◽  
Measurement Techniques ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Aerosol Optical Properties ◽  
Biomass Burning Aerosol

Abstract. The total effect of aerosols, both directly and on cloud properties, remains the biggest source of uncertainty in anthropogenic radiative forcing on the climate. Correct characterization of intensive aerosol optical properties, particularly in conditions where absorbing aerosol is present, is a crucial factor in quantifying these effects. The southeast Atlantic Ocean (SEA), with seasonal biomass burning smoke plumes overlying and mixing with a persistent stratocumulus cloud deck, offers an excellent natural laboratory to make the observations necessary to understand the complexities of aerosol–cloud–radiation interactions. The first field deployment of the NASA ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) campaign was conducted in September of 2016 out of Walvis Bay, Namibia. Data collected during ORACLES-2016 are used to derive aerosol properties from an unprecedented number of simultaneous measurement techniques over this region. Here, we present results from six of the eight independent instruments or instrument combinations, all applied to measure or retrieve aerosol absorption and single-scattering albedo. Most but not all of the biomass burning aerosol was located in the free troposphere, in relative humidities typically ranging up to 60 %. We present the single-scattering albedo (SSA), absorbing and total aerosol optical depth (AAOD and AOD), and absorption, scattering, and extinction Ångström exponents (AAE, SAE, and EAE, respectively) for specific case studies looking at near-coincident and near-colocated measurements from multiple instruments, and SSAs for the broader campaign average over the month-long deployment. For the case studies, we find that SSA agrees within the measurement uncertainties between multiple instruments, though, over all cases, there is no strong correlation between values reported by one instrument and another. We also find that agreement between the instruments is more robust at higher aerosol loading (AOD400>0.4). The campaign-wide average and range shows differences in the values measured by each instrument. We find the ORACLES-2016 campaign-average SSA at 500 nm (SSA500) to be between 0.85 and 0.88, depending on the instrument considered (4STAR, AirMSPI, or in situ measurements), with the interquartile ranges for all instruments between 0.83 and 0.89. This is consistent with previous September values reported over the region (between 0.84 and 0.90 for SSA at 550nm). The results suggest that the differences observed in the campaign-average values may be dominated by instrument-specific spatial sampling differences and the natural physical variability in aerosol conditions over the SEA, rather than fundamental methodological differences.

scholarly journals Radiative Impact of Fireworks at a Tropical Indian Location: A Case Study

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
B. P. Singh ◽  
A. K. Srivastava ◽  
S. Tiwari ◽  
S. Singh ◽  
R. K. Singh ◽  
...  
Keyword(s):  
Behavioral Change ◽  
Radiative Forcing ◽  
Gangetic Plain ◽  
Scattering Coefficients ◽  
Aerosol Absorption ◽  
Aerosol Scattering ◽  
Radiative Impact ◽  
Diwali Festival ◽  
Indo Gangetic Plain

During Diwali festival, extensive burning of crackers and fireworks is made. Weeklong intensive observational campaign for aerosol study was carried out at a representative urban location in the eastern Indo-Gangetic Plain (IGP), Varanasi (25.3°N, 83.0°E), from October 29 to November 04, 2005 (Diwali on November 01, 2005), to investigate behavioral change of aerosol properties and radiative forcing between firework affected and nonaffected periods. Results show a substantial increase (~27%) in aerosol optical depth, aerosol absorption coefficients, and aerosol scattering coefficients during affected period as compared to non-affected periods. Magnitudes of radiative forcing at top of atmosphere during affected and non-affected periods are found to be +10 ± 1 and +12 ± 1 Wm−2, respectively, which are −31 ± 7 and −17 ± 5 Wm−2, respectively, at surface. It suggests an additional cooling of ~20% at top of atmosphere, ~45% cooling at surface, and additional atmospheric heating of 0.23 Kday−1during fireworks affected period, which is ~30% higher than the non-affected period average.

scholarly journals Evaluating Model Parameterizations of Submicron Aerosol Scattering and Absorption with In Situ Data from ARCTAS 2008

2016 ◽  
Author(s):  
M. J. Alvarado ◽  
C. R. Lonsdale ◽  
H. L. Macintyre ◽  
H. Bian ◽  
M. Chin ◽  
...  
Keyword(s):  
Optical Properties ◽  
Size Distribution ◽  
Aerosol Size Distribution ◽  
Visible Radiation ◽  
Submicron Aerosol ◽  
In Situ Data ◽  
Aerosol Absorption ◽  
Aerosol Scattering ◽  
The Impact

Abstract. Accurate modeling of the scattering and absorption of ultraviolet and visible radiation by aerosols is essential for accurate simulations of atmospheric chemistry and climate. Closure studies using in situ measurements of aerosol scattering and absorption can be used to evaluate and improve models of aerosol optical properties without interference from model errors in aerosol emissions, transport, chemistry, or deposition rates. Here we evaluate the ability of four externally mixed, fixed size distribution parameterizations used in global models to simulate submicron aerosol scattering and absorption at three wavelengths using in situ data gathered during the 2008 Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. The four models are the NASA Global Modeling Initiative (GMI) Combo model, GEOS-Chem v9-02, the baseline configuration of a version of GEOS-Chem with online radiative transfer calculations (called GC-RT), and the Optical Properties of Aerosol and Clouds (OPAC v3.1) package. We also use the ARCTAS data to perform the first evaluation of the ability of the Aerosol Simulation Program (ASP v2.1) to simulate submicron aerosol scattering and absorption when in situ data on the aerosol size distribution is used, and examine the impact of different mixing rules for black carbon (BC) on the results. We find that the GMI model tends to overestimate submicron scattering and absorption at shorter wavelengths by 10–23 %, and that GMI has smaller absolute mean biases for submicron absorption than OPAC v3.1, GEOS-Chem v9-02, or GC-RT. However, the changes to the density and refractive index of BC in GC-RT improve the simulation of submicron aerosol absorption at all wavelengths relative to GEOS-Chem v9-02. Adding in situ size distribution information, as in ASP v2.1, improves model performance for scattering but not for absorption, likely due to the assumption in ASP v2.1 that BC is present at a constant mass fraction through out the aerosol size distribution. Using a core-shell mixing state in ASP overestimates aerosol absorption, especially for the fresh biomass burning aerosol measured in ARCTAS-B, suggesting the need for time-varying mixing states in future versions of ASP.

scholarly journals Seasonal differences in the vertical profiles of aerosol optical properties over rural Oklahoma

2011 ◽  
Vol 11 (4) ◽  
pp. 11939-11957 ◽  
Author(s):  
E. Andrews ◽  
P. J. Sheridan ◽  
J. A. Ogren
Keyword(s):  
Seasonal Variability ◽  
Seasonal Cycle ◽  
Gulf Coast ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Vertical Profiles ◽  
Seasonal Differences ◽  
Aerosol Loading ◽  
Aerosol Absorption ◽  
Aerosol Scattering

Abstract. A small airplane made more than 450 aerosol optical property (light absorption and light scattering) vertical profile measurements (up to 4 km) over a rural Oklahoma site between March 2000 and July 2005. These profiles suggest significant seasonal differences in aerosol properties. The highest amounts of scattering and absorbing aerosol are observed during the summer, while the relative contribution of aerosol absorption is highest in the winter (i.e., single scattering albedo is lowest in winter). Aerosol absorption generally decreased with altitude below ∼1.5 km and then was relatively constant above that. Aerosol scattering decreased sharply with altitude below ∼1.5 km but, unlike absorption, also decreased at higher altitudes, albeit less sharply. The seasonal variability observed for aerosol loading is consistent with other aerosol measurements in the region including AERONET aerosol optical depth (AOD), CALIPSO vertical profiles, and IMPROVE aerosol mass. The column averaged single scattering albedo derived from in situ airplane measurements shows a similar seasonal cycle as the AERONET single scattering albedo inversion product, but a comparison of aerosol asymmetry parameter from airplane and AERONET platforms suggests differences in seasonal variability. The observed seasonal cycle of aerosol loading corresponds with changes in air mass back trajectories: the aerosol scattering was higher when transport was from polluted areas (e.g., the Gulf Coast) and lower when the air came from cleaner regions and/or the upper atmosphere.

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