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

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

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-10661-2011 ◽

2011 ◽

Vol 11 (20) ◽

pp. 10661-10676 ◽

Cited By ~ 34

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.

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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

10.5194/acp-2019-657 ◽

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

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

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-9041-2014 ◽

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.

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Modulation of the aerosol absorption and single-scattering albedo due to synoptic scale and sea breeze circulations: United Arab Emirates experiment perspective

Journal of Geophysical Research Atmospheres ◽

10.1029/2006jd007139 ◽

2007 ◽

Vol 112 (D5) ◽

Cited By ~ 5

Author(s):

J. Remiszewska ◽

P. J. Flatau ◽

K. M. Markowicz ◽

E. A. Reid ◽

J. S. Reid ◽

...

Keyword(s):

United Arab Emirates ◽

Sea Breeze ◽

Single Scattering ◽

Single Scattering Albedo ◽

Synoptic Scale ◽

Aerosol Absorption

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Global maps of aerosol single scattering albedo using combined CERES-MODIS retrieval

10.5194/acp-2021-521 ◽

2021 ◽

Author(s):

Archana Devi ◽

Sreedharan Krishnakumari Satheesh

Keyword(s):

Climate Models ◽

Radiant Energy ◽

Energy System ◽

Single Scattering ◽

Global Scale ◽

Single Scattering Albedo ◽

Accurate Information ◽

Climatic Impact ◽

Aerosol Absorption ◽

Moderate Resolution Imaging Spectroradiometer

Abstract. Single Scattering Albedo (SSA) is a leading contributor to the uncertainty in aerosol radiative impact assessments. Therefore accurate information on aerosol absorption is required on a global scale. In this study, we have applied a multi-satellite algorithm to retrieve SSA using the concept of ‘critical optical depth.’ Global maps of SSA were generated following this approach using spatially and temporally collocated data from Clouds and the Earth’s Radiant Energy System (CERES) and Moderate Resolution Imaging Spectroradiometer (MODIS) sensors on board Terra and Aqua satellites. The method has been validated using the data from aircraft-based measurements of various field campaigns. The retrieval uncertainty is ±0.03 and depends on both the surface albedo and aerosol absorption. Global mean SSA estimated over land and ocean is 0.93 and 0.97, respectively. Seasonal and spatial distribution of SSA over various regions are also presented. The global maps of SSA, thus derived with improved accuracy, provide important input to climate models for assessing the climatic impact of aerosols on regional and global scales.

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Vertical profiles of submicron aerosol single scattering albedo over the Indian region immediately before monsoon onset and during its development: research from the SWAAMI field campaign

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-4031-2020 ◽

2020 ◽

Vol 20 (6) ◽

pp. 4031-4046

Author(s):

Mohanan R. Manoj ◽

Sreedharan K. Satheesh ◽

Krishnaswamy K. Moorthy ◽

Hugh Coe

Keyword(s):

Active Phase ◽

Single Scattering ◽

Monsoon Onset ◽

Single Scattering Albedo ◽

Transfer Model ◽

Heating Rates ◽

Atmospheric Measurements ◽

Middle Troposphere ◽

Submicron Aerosol ◽

Aerosol Absorption

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 Facility for Airborne Atmospheric Measurements (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 (<3 km) over the Indo-Gangetic Plains (IGP), prior to the monsoon onset, with a west-to-east gradient; lower values occurred in the north-western arid regions, peaking in the central IGP and somewhat decreasing towards the eastern end. During the active phase of the monsoon, the SSA is found to increase remarkably, indicating far less absorption. Nevertheless, significant aerosol absorption persisted in the lower and middle troposphere over the IGP. Inputting these SSA and extinction profiles into a radiative transfer model, we examined the effects of using height-resolved information in estimating atmospheric heating rates due to aerosols, over similar estimates made using a single columnar value. It was noted that use of a single SSA value leads to an underestimation (overestimation) of the heating rates over regions with low (high) SSA, emphasizing the importance of height-resolved information. Further, the use of realistic profiles showed significant heating of the atmosphere by submicron aerosol absorption at the middle troposphere, which may have strong implications for clouds and climate.

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Vertical profiles of light absorption and scattering associated with black-carbon particle fractions in the springtime Arctic above 79° N

10.5194/acp-2019-785 ◽

2019 ◽

Cited By ~ 1

Author(s):

W. Richard Leaitch ◽

John K. Kodros ◽

Megan D. Willis ◽

Sarah Hanna ◽

Hannes Schulz ◽

...

Keyword(s):

Optical Properties ◽

Absorption Coefficient ◽

Black Carbon ◽

Light Absorption ◽

Single Scattering ◽

Single Scattering Albedo ◽

The Arctic ◽

Vertical Profiles ◽

Near Surface ◽

Arctic Atmosphere

Abstract. Despite the potential importance of black carbon (BC) to radiative forcing of the Arctic atmosphere, vertically-resolved measurements of the particle light scattering coefficient (Bsp) and light absorption coefficient (Bap) in the springtime Arctic atmosphere are infrequent, especially measurements at latitudes at or above 80oN. Here, relationships among vertically-distributed aerosol optical properties Bap, Bsp, and single scattering albedo or SSA), particle microphysics and particle chemistry are examined for a region of the Canadian archipelago between 79.9oN and 83.4oN from near the surface to 500 hPa. Airborne data collected during April, 2015, are combined with ground-based observations from the observatory at Alert, Nunavut and simulations from the GEOS-Chem-TOMAS model (Kodros et al., 2018) to increase our knowledge of the effects of BC on light absorption in the Arctic troposphere. The results are constrained for Bsp less than 15 Mm-1, which represent 98% of the observed Bsp, because the single scattering albedo (SSA) has a tendency to be lower at lower Bsp, resulting in a larger relative contribution to Arctic warming. At 18.4 m2 g-1, the average BC mass absorption coefficient (MAC) from the combined airborne and Alert observations is substantially higher than the two averaged modelled MAC values (9.5 m2 g-1 and 7.0 m2 g-1) for two different internal mixing assumptions, the latter of which is based on previous observations. The higher observed MAC value may be explained by an underestimation of BC and possible differences in BC microphysics and morphologies between the observations and model. We present Bap and SSA based on the assumption that Bap is overestimated in the observations in addition to the assumption that the higher MAC is explained. Median values of the measured Bap, rBC and organic component of particles all increase by a factor of 1.8±0.1 going from near-surface to 750 hPa, and values higher than the surface persist to 600 hPa. Modelled BC, organics, and Bap agree with the near-surface measurements, but do not reproduce the higher values observed between 900 hPa and 600 hPa. The differences between modelled and observed optical properties follow the same trend as the differences between the modelled and observed concentrations of the carbonaceous components (black and organic). Some discrepancies in the model may be due to the use of a relatively low imaginary refractive index of BC as well as by the ejection of biomass burning particles only into the boundary layer at sources. For the assumption of the higher observed MAC value, the SSA range between 0.88 and 0.94, which is significantly lower than other recent estimates for the Arctic, in part reflecting the constraint of Bsp <15 Mm-1. The large uncertainties in measuring optical properties and BC as well as the large differences between measured and modelled values, here and in the literature, argue for improved measurements of BC and light absorption by BC as well as more vertical profiles of aerosol chemistry, microphysics, and other optical properties in the Arctic.

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Vertical profiles of urban aerosol complex refractive index in the frame of ESQUIF airborne measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-901-2008 ◽

2008 ◽

Vol 8 (4) ◽

pp. 901-919 ◽

Cited By ~ 35

Author(s):

J.-C. Raut ◽

P. Chazette

Keyword(s):

Refractive Index ◽

Complex Refractive Index ◽

Single Scattering ◽

In Situ Measurements ◽

Single Scattering Albedo ◽

Vertical Profiles ◽

Airborne Measurements ◽

Paris Area

Abstract. A synergy between lidar, sunphotometer and in situ measurements has been applied to airborne observations performed during the Etude et Simulation de la QUalité de l'air en Ile-de-France (ESQUIF), enabling the retrieval of vertical profiles for the aerosol complex refractive index (ACRI) and single-scattering albedo with a vertical resolution of 200 m over Paris area. The averaged value over the entire planetary boundary layer (PBL) for the ACRI is close to 1.51(±0.02)–i0.017(±0.003) at 532 nm. The single-scattering albedo of the corresponding aerosols is found to be ~0.9 at the same wavelength. A good agreement is found with previous studies for urban aerosols. A comparison of vertical profiles of ACRI with simulations combining in situ measurements and relative humidity (RH) profiles has highlighted a modification in aerosol optical properties linked to their history and the origin of the air mass. The determination of ACRI in the atmospheric column enabled to retrieve vertical profiles of extinction coefficient in accordance with lidar profiles measurements.

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Vertical profiles of urban aerosol complex refractive index in the frame of ESQUIF airborne measurements

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-7-10799-2007 ◽

2007 ◽

Vol 7 (4) ◽

pp. 10799-10835 ◽

Cited By ~ 2

Author(s):

J.-C. Raut ◽

P. Chazette

Keyword(s):

Refractive Index ◽

Complex Refractive Index ◽

Single Scattering ◽

In Situ Measurements ◽

Single Scattering Albedo ◽

Vertical Profiles ◽

Airborne Measurements ◽

Paris Area

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Measurements of aerosol absorption and scattering in the Mexico City Metropolitan Area during the MILAGRO field campaign: a comparison of results from the T0 and T1 sites

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-8-12625-2008 ◽

2008 ◽

Vol 8 (4) ◽

pp. 12625-12663 ◽

Cited By ~ 2

Author(s):

N. A. Marley ◽

J. S. Gaffney ◽

T. Castro ◽

A. Salcido ◽

J. Frederick

Keyword(s):

Mexico City ◽

Diffuse Radiation ◽

Ground Level ◽

Forward Direction ◽

Single Scattering ◽

Field Campaign ◽

Clear Sky ◽

Aerosol Absorption ◽

Aerosol Scattering ◽

Solar Noon

Abstract. Measurements of aerosol absorption and scattering were obtained in Mexico City during the MILAGRO (Megacity Initiative: Local and Global Research Observations) field campaign in March 2006. A comparison of aerosol absorption and scattering was obtained in Mexico City at site T0 located in the northern part of Mexico City at the Instituto Mexicano del Petróleo Laboratories and at site T1 located at the Universidad Tecnológica de Tecamac, 18 miles northwest of T0. Hourly averages of aerosol absorption were similar at both sites, ranging from 6–93 Mm−1 with an average of 31 Mm−1 at T0; and from 2–104 Mm−1 with an average of 19 Mm−1 at T1. Aerosol scattering at T0 ranged from 16–344 Mm−1 with an average of 105 Mm−1; while the scattering values at T1 were lower than T0 ranging from 2–136 with an average of 53 Mm−1. Aerosol single scattering albedos (SSAs) were determined at both sites using these data. SSAs at T1 ranged from 0.44–0.90 with an average 0.75 as compared to hose at T0, range 0.51–0.93 with an average of 0.77. Broadband UV-B intensity was found to be higher at site T0, with an average of 64 μW/cm2 at solar noon, than at site T1, which had an average of 54 μW/cm2 at solar noon. Comparisons of clear-sky modeled UV-B intensities with the simultaneous UV-B measurements obtained at site T0 and at site T1 for cloudless days indicate a larger diffuse radiation field at site T0 than at site T1. The determination of aerosol scattering Ångstrom coefficient at T0 suggests the larger diffuse radiation is due to the predominance of submicron aerosols at T0 with aerosol scattering of UV-B radiation peaked in the forward direction, leading to the enhancement observed at ground level.

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