scholarly journals Measurements of aerosol intensive properties over Visakhapatnam, India for 2007

2011 ◽  
Vol 29 (6) ◽  
pp. 973-985 ◽  
Author(s):  
K. Niranjan ◽  
B. Spandana ◽  
T. Anjana Devi ◽  
V. Sreekanth ◽  
B. L. Madhavan
Keyword(s):  
Asymmetry Parameter ◽  
Radiative Forcing ◽  
Single Scattering ◽  
Peninsular India ◽  
Aerosol Radiative Forcing ◽  
Scattering Coefficients ◽  
Aerosol Absorption ◽  
Angular Scattering ◽  
The Asymmetry ◽  
First Time

Abstract. Information on the aerosol intensive properties like Single Scattering Albedo (SSA) and asymmetry parameter are very limited, particularly over the peninsular India, though extensive reports are available on the aerosol bulk properties. In view of the importance of these parameters in evaluating the aerosol radiative forcing, we present for the first time the temporal variation in SSA with measurements on aerosol absorption and scattering coefficients over Visakhapatnam (17.72° N, 83.32° E; located on the east coast of India) for the year 2007. The inferred SSA was in the range of 0.65 and 0.9 with an annual mean of 0.76 ± 0.013 and with a probable value of 0.80, indicating a marginal atmospheric warming over the region. The mixed layer contribution to column Aerosol Optical depth is found to be 35 % in summer while it is well above 35 % in winter, indicating the confinement of aerosol within the boundary layer during winter. The asymmetry parameter which represents the angular scattering in radiative forcing estimation is found to be around 0.65 ± 0.1 for the location. The day to day variability in SSA is found to be well correlated with the variations in surface BC mass concentrations and/or the relative dominance of the fine/coarse mode aerosol. The results are discussed in light of the aerosol physical and optical properties and the asymmetry parameter.

scholarly journals Multi-Satellite Retrieval of SSA using OMI-MODIS algorithm

2018 ◽  
Author(s):  
Kruthika Eswaran ◽  
Sreedharan Krishnakumari Satheesh ◽  
Jayaraman Srinivasan
Keyword(s):  
Radiative Forcing ◽  
Single Scattering ◽  
Retrieval Algorithm ◽  
Ozone Monitoring Instrument ◽  
Aerosol Composition ◽  
Aerosol Radiative Forcing ◽  
Aerosol Absorption ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Absorbing Aerosols ◽  
Aerosol Type

Abstract. Single scattering albedo (SSA) represents a unique identification of aerosol type and aerosol radiative forcing. However, SSA retrievals are highly uncertain due cloud contamination and aerosol composition. Recent improvement in the SSA retrieval algorithm has combined the superior cloud masking technique of Moderate Resolution Imaging Spectroradiometer (MODIS) and the better sensitivity of Ozone Monitoring Instrument (OMI) to aerosol absorption. The combined OMI-MODIS algorithm has been validated over a small spatial and temporal scale only. The present study validates the algorithm over global oceans for the period 2008–2012. The geographical heterogeneity in the aerosol type and concentration over the Atlantic Ocean, the Arabian Sea and the Bay of Bengal was useful to delineate the effect of aerosol type on the retrieval algorithm. We also noted that OMI overestimates SSA when absorbing aerosols were present closer to the surface. We attribute this overestimation to data discontinuity in the aerosol height climatology derived from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite. OMI uses pre-defined aerosol heights over regions where CALIPSO climatology is not present leading to overestimation of SSA. The importance of aerosol height was also studied using the Santa Barbara DISORT radiative transfer (SBDART) model. The results from the joint retrieval were validated with ground-based measurements and it was seen that OMI-MODIS SSA retrievals were better constrained than OMI only retrieval.

scholarly journals Simulations of Contrail Optical Properties and Radiative Forcing for Various Crystal Shapes

2011 ◽  
Vol 50 (8) ◽  
pp. 1740-1755 ◽  
Author(s):  
Krzysztof M. Markowicz ◽  
Marcin L. Witek
Keyword(s):  
Optical Properties ◽  
Asymmetry Parameter ◽  
Radiative Forcing ◽  
Surface Albedo ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Crystal Shape ◽  
Crystal Shapes ◽  
The Mean ◽  
The Asymmetry

AbstractThe aim of this study is to investigate the sensitivity of radiative-forcing computations to various contrail crystal shape models. Contrail optical properties in the shortwave and longwave ranges are derived using a ray-tracing geometric method and the discrete dipole approximation method, respectively. Both methods present good correspondence of the single-scattering albedo and the asymmetry parameter in a transition range (3–8 μm). There are substantial differences in single-scattering properties among 10 crystal models investigated here (e.g., hexagonal columns and plates with different aspect ratios, and spherical particles). The single-scattering albedo and the asymmetry parameter both vary by up to 0.1 among various crystal shapes. The computed single-scattering properties are incorporated in the moderate-resolution atmospheric radiance and transmittance model (MODTRAN) radiative transfer code to simulate solar and infrared fluxes at the top of the atmosphere. Particle shapes have a strong impact on the contrail radiative forcing in both the shortwave and longwave ranges. The differences in the net radiative forcing among optical models reach 50% with respect to the mean model value. The hexagonal-column and hexagonal-plate particles show the smallest net radiative forcing, and the largest forcing is obtained for the spheres. The balance between the shortwave forcing and longwave forcing is highly sensitive with respect to the assumed crystal shape and may even change the sign of the net forcing. The optical depth at which the mean diurnal radiative forcing changes sign from positive to negative varies from 4.5 to 10 for a surface albedo of 0.2 and from 2 to 6.5 for a surface albedo of 0.05. Contrails are probably never that optically thick (except for some aged contrail cirrus), however, and so will not have a cooling effect on climate.

scholarly journals Heterogeneous OH oxidation of secondary brown carbon aerosol

2018 ◽  
Author(s):  
Elijah G. Schnitzler ◽  
Jonathan P. D. Abbatt
Keyword(s):  
Optical Properties ◽  
Single Scattering ◽  
Trace Gas ◽  
Absorption Enhancement ◽  
Brown Carbon ◽  
Scattering Coefficients ◽  
Aerosol Absorption ◽  
In Series ◽  
First Time ◽  
Slow Absorption

Abstract. Light-absorbing organic aerosol, or brown carbon (BrC), has significant but poorly-constrained effects on climate; for example, oxidation in the atmosphere may alter its optical properties, leading to absorption enhancement or bleaching. Here, we investigate for the first time the effects of heterogeneous OH oxidation on the optical properties of a laboratory surrogate of secondary BrC in a series of photo-oxidation chamber experiments. The BrC surrogate was generated from aqueous resorcinol, or 1,3-dihydroxybenzene, and H2O2 exposed to > 300 nm radiation, atomized, passed through trace gas denuders, and injected into the chamber, which was conditioned to either 15 or 60 % relative humidity (RH). Aerosol absorption and scattering coefficients and single scattering albedo (SSA) at 405 nm were measured using a photo-acoustic spectrometer. At 60 % RH, upon OH exposure, absorption first increased, and the SSA decreased sharply. Subsequently, absorption decreased faster than scattering, and SSA increased gradually. Comparisons to the modelled trend in SSA, based on Mie theory calculations, confirm that the observed trend is due to chemical evolution, rather than slight changes in particle size. The initial absorption enhancement is likely due to molecular functionalization and/or oligomerization, and the bleaching to fragmentation. By contrast, at 15 % RH, slow absorption enhancement was observed, without appreciable bleaching. A multi-layer kinetics model, consisting of two surface reactions in series, was constructed to provide further insights regarding the RH-dependence of the optical evolution. Candidate parameters suggest that the oxidation is efficient, with uptake coefficients on the order of unity, and the aerosol is very viscous, even at 60 % RH. At 15 % RH, the aerosol will be viscous enough to confine products of fragmentation, leading to their recombination, such that little bleaching is observed on the experimental timescale. These results further the current understanding of the complex processing of BrC that may occur in the atmosphere.

scholarly journals Heterogeneous OH oxidation of secondary brown carbon aerosol

2018 ◽  
Vol 18 (19) ◽  
pp. 14539-14553 ◽  
Author(s):  
Elijah G. Schnitzler ◽  
Jonathan P. D. Abbatt
Keyword(s):  
Optical Properties ◽  
Single Scattering ◽  
Trace Gas ◽  
Absorption Enhancement ◽  
Brown Carbon ◽  
Scattering Coefficients ◽  
Aerosol Absorption ◽  
Photoacoustic Spectrometer ◽  
In Series ◽  
First Time

Abstract. Light-absorbing organic aerosol, or brown carbon (BrC), has significant but poorly constrained effects on climate; for example, oxidation in the atmosphere may alter its optical properties, leading to absorption enhancement or bleaching. Here, we investigate for the first time the effects of heterogeneous OH oxidation on the optical properties of a laboratory surrogate of aqueous, secondary BrC in a series of photo-oxidation chamber experiments. The BrC surrogate was generated from aqueous resorcinol, or 1,3-dihydroxybenzene, and H2O2 exposed to >300 nm radiation that is atomized, passed through trace gas denuders, and injected into the chamber, which was conditioned to either 15 % or 60 % relative humidity (RH). Aerosol absorption and scattering coefficients and single scattering albedo (SSA) at 405 nm were measured using a photoacoustic spectrometer. At 60 % RH, upon OH exposure, absorption first increased, and the SSA decreased sharply. Subsequently, absorption decreased faster than scattering, and SSA increased gradually. Comparisons to the modelled trend in SSA, based on Mie theory calculations, confirm that the observed trend is due to chemical evolution, rather than slight changes in particle size. The initial absorption enhancement is likely due to molecular functionalization and/or oligomerization and the bleaching to fragmentation. By contrast, at 15 % RH, slow absorption enhancement was observed without appreciable bleaching. A multi-layer kinetics model, consisting of two surface reactions in series, was constructed to provide further insights regarding the RH dependence of the optical evolution. Candidate parameters suggest that the oxidation is efficient, with uptake coefficients on the order of unity. The parameters also suggest that, as RH decreases, reactivity decreases and aerosol viscosity increases, such that particles are well-mixed at 60 % RH but not at 15 % RH. These results further the current understanding of the complex processing of BrC that may occur in the atmosphere.

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 Contrasting variation in aerosol optical properties during dust episodes in the Middle East and Southwest Asia: Model results and ground measurement

2019 ◽  
Vol 99 ◽  
pp. 04006
Author(s):  
Khan Alam ◽  
Maqbool Ahmad
Keyword(s):  
Middle East ◽  
Radiative Forcing ◽  
Single Scattering ◽  
Dust Storms ◽  
Radiative Properties ◽  
Southwest Asia ◽  
Gulf Region ◽  
Aerosol Radiative Forcing ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
Using Data

Dust storms deteriorated air quality over the Gulf Region, Iraq, Iran, and Pakistan during the last decade. The purpose of this study is to investigate the changes in aerosol optical and radiative properties during a dust episode over the various locations in the Middle East and Southwest Asia using data from the MODerate resolution Imaging Spectroradiometer (MODIS) and the Aerosol Robotic Network (AERONET) during March, 2012. Maximum aerosol optical depth (AOD) values were found to be 2.18, 1.30, 4.33 and 1.80 over Lahore, Kanpur, Kaust, and Mezaira, respectively. The Volume Size Distributions, Single Scattering Albedo, Refractive Index, and Asymmetry parameter indicated that coarse mode aerosols were predominant relative to fine mode aerosols during the dust event. The average shortwave aerosol radiative forcing (ARF) values at the earth’s surface were found to be -96±45 W m-2, -86±22 W m-2, -77±51 W m-2, and -75±40 W m-2, over Lahore, Kanpur, Kaust and Mezaira, respectively. Likewise, the averaged ARF values over Lahore, Kanpur, Kaust and Mezaira at the top of the atmosphere (TOA) were found to be -45±25 W m-2, -27±9 W m-2, -41±29 W m-2, and -75±40 W m-2, respectively. The large differences between surface and TOA forcing produced significant heating within the atmosphere.

scholarly journals Direct Aerosol Radiative Forcing Uncertainty Based on a Radiative Perturbation Analysis

2010 ◽  
Vol 23 (19) ◽  
pp. 5288-5293 ◽  
Author(s):  
Norman G. Loeb ◽  
Wenying Su
Keyword(s):  
Radiative Forcing ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Aerosol Radiative Forcing ◽  
Clear Sky ◽  
Radiative Perturbation ◽  
Sky Conditions ◽  
Global Mean ◽  
Aerosol Properties ◽  
Aerosol Radiative

Abstract To provide a lower bound for the uncertainty in measurement-based clear- and all-sky direct aerosol radiative forcing (DARF), a radiative perturbation analysis is performed for the ideal case in which the perturbations in global mean aerosol properties are given by published values of systematic uncertainty in Aerosol Robotic Network (AERONET) aerosol measurements. DARF calculations for base-state climatological cloud and aerosol properties over ocean and land are performed, and then repeated after perturbing individual aerosol optical properties (aerosol optical depth, single-scattering albedo, asymmetry parameter, scale height, and anthropogenic fraction) from their base values, keeping all other parameters fixed. The total DARF uncertainty from all aerosol parameters combined is 0.5–1.0 W m−2, a factor of 2–4 greater than the value cited in the Intergovernmental Panel on Climate Change’s (IPCC’s) Fourth Assessment Report. Most of the total DARF uncertainty in this analysis is associated with single-scattering albedo uncertainty. Owing to the greater sensitivity to single-scattering albedo in cloudy columns, DARF uncertainty in all-sky conditions is greater than in clear-sky conditions, even though the global mean clear-sky DARF is more than twice as large as the all-sky DARF.

scholarly journals Estimates of aerosol absorption over India using multi-satellite retrieval

2013 ◽  
Vol 31 (10) ◽  
pp. 1773-1778 ◽  
Author(s):  
D. Narasimhan ◽  
S. K. Satheesh
Keyword(s):  
Regional Distribution ◽  
Single Scattering ◽  
Ozone Monitoring Instrument ◽  
Satellite Retrieval ◽  
Aerosol Absorption ◽  
Moderate Resolution ◽  
Indian Landmass ◽  
Resolution Imaging ◽  
Moderate Resolution Imaging Spectroradiometer ◽  
First Time

Abstract. Aerosol absorption is poorly quantified because of the lack of adequate measurements. It has been shown that the Ozone Monitoring Instrument (OMI) aboard EOS-Aura and the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard EOS-Aqua, which fly in formation as part of the A-train, provide an excellent opportunity to improve the accuracy of aerosol retrievals. Here, we follow a multi-satellite approach to estimate the regional distribution of aerosol absorption over continental India for the first time. Annually and regionally averaged aerosol single-scattering albedo over the Indian landmass is estimated as 0.94 ± 0.03. Our study demonstrates the potential of multi-satellite data analysis to improve the accuracy of retrieval of aerosol absorption over land.

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.

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