In-situ measurements of atmospheric aerosols by using Integrating Nephelometer over a semi-arid station, southern India

Gopal, K. Rama; Arafath, S.Md.; Lingaswamy, A.P.; Balakrishnaiah, G.; Kumari, Shikha; Devi, K. Uma; Reddy, Narendra; Reddy, K. Suresh Kumar; Reddy, M. Penchal; Reddy, R.R.; Babu, S. Suresh

doi:10.1016/j.atmosenv.2013.12.009

Cited by 35 publications

(15 citation statements)

References 40 publications

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“…Moreover, the g interval 0.50-0.75 was analysed in detail since this range is in agreement with the variability of asymmetry factor observed across Europe (Pandolfi et al, 2018) and because values of g larger than 0.50 have often been reported in the literature (see e.g. Andrews et al, 2006;D'Almeida et al, 1991;Donateo et al, 2018;Formenti et al, 2000;Hartley & Hobbs, 2001;Horvath et al, 2016;Horvath et al, 2018;Gopal et al, 2014) It is noteworthy that, considering both g=0.35 and g=0.50, PP_UniMI approach response to g variations compared to g=0.75 was smaller than the one of PaM approach.…”

Section: Sensitivity Tests On Asymmetry Factor Assumptionsupporting

confidence: 71%

Applicability of benchtop multi-wavelength polar photometers to off-line measurements of the Multi-Angle Absorption Photometer (MAAP) samples

Valentini

Bernardoni

Bolzacchini

et al. 2021

Journal of Aerosol Science

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In this study, the applicability of a benchtop polar photometer (PP_UniMI) to retrieve multi-wavelength aerosol absorption coefficient data by off-line measurements of the Multi-Angle Absorption Photometer (MAAP) sample spots is presented. MAAP is a widespread single wavelength online instrument providing the aerosol absorption coefficient and the equivalent black carbon concentration. In this work, MAAP samples collected during four different campaigns were analysed off-line with PP_UniMI.First of all, data from PP_UniMI and MAAP were compared to investigate contributions to measurement uncertainties. In particular, the role of the following assumptions performed in the MAAP was investigated:-reconstructing angular distribution of light scattered by filter samples from measurements at three fixed angles using analytical functions; -setting the fraction of the back-scattered radiation by the blank filter (BM) at a fixed value BM=0.7:-assuming a fixed value for the asymmetry factor g=0.75.Samples collected at several sites showed an agreement within 5% when data from the two instruments were retrieved using the same approximations (i.e. backscattered radiation from the filter matrix BM set at a fixed value, phase functions reconstructed by analytical functions from measurements at 3 angles, same asymmetry factor) in the data retrieval algorithm. Conversely, larger differences (14% on average) between off-line measurements and averaged MAAP data were obtained when the high-angular resolved information available by PP_UniMI was exploited. By analysing the role of MAAP assumptions for σap retrieval, it resulted that fixing BM=0.7 was the main responsible for the detected differences. Indeed, highangular resolved off-line measurements by PP_UniMI allow to directly measure BM, obtaining BM=0.88 on white spots. It is noteworthy that the observed results were similar at all considered sites, so they proved to be independent of the aerosol type and can likely be attributed to instrumental effects. Moreover, a sensitivity test was carried out also to check the impact of the fixed value used for the asymmetry factor (set at g=0.75 in both instruments). Varying g values within the typical range for ambient aerosol (0.50-0.75) the estimate of aerosol absorbance ABS (directly obtained from PP_UniMI measurements and linked to σap) was affected by 8% at most, thus being a minor source of uncertainty in the calculation. The effect of the variability in blank spots used for off-line analyses was also evaluated and resulted in a contribution smaller than 3% to the uncertainty of the methodology employed.Finally, the possibility of exploiting multi-wavelength assessment of absorption coefficients is an added value of PP_UniMI; indeed, it allows to estimate the contribution of different aerosol sources and components to the absorption coefficient using MAAP tapes used in present or past campaigns.

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Section: Sensitivity Tests On Asymmetry Factor Assumptionsupporting

confidence: 71%

Applicability of benchtop multi-wavelength polar photometers to off-line measurements of the Multi-Angle Absorption Photometer (MAAP) samples

Valentini

Bernardoni

Bolzacchini

et al. 2021

Journal of Aerosol Science

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“…They reported a range of g between 0.3 and 0.6 at a wavelength of 550 nm and scaled to a relative humidity (RH) of 30%. Gopal, et al [21] conducted one year of ground-based nephelometer measurements at Anantapur, a semi-arid region in southern India and reported a range of g between 0.53 and 0.65 at a wavelength of 550 nm.…”

Section: Measurements Of the Asymmetry Parameter G In The Ambient Atmmentioning

confidence: 99%

“…The third-order polynomial approximation g A_fit (Equation (9)) giving the asymmetry parameter as function of the backscatter fraction b suggested by Arnott [19] and published by Andrews, et al [5] has been used by Ramachandran and Rajesh [20] and by Gopal, et al [21] to derive the asymmetry parameter g from nephelometer measurements of b. Ramachandran and Rajesh [20] conducted an airborne campaign measuring vertical profiles in the lower troposphere at four locations in tropical India. They reported a range of g between 0.3 and 0.6 at a wavelength of 550 nm and scaled to a relative humidity (RH) of 30%.…”

Section: Measurements Of the Asymmetry Parameter G In The Ambient Atmmentioning

confidence: 99%

Parameterization of the Aerosol Upscatter Fraction as Function of the Backscatter Fraction and Their Relationships to the Asymmetry Parameter for Radiative Transfer Calculations

Moosmüller

Ogren

2017

Atmosphere

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Abstract:Simple analytical approximations for aerosol radiative forcing generally contain the aerosol upscatter fraction (the fraction of scattered light that is scattered into the upper hemisphere), while ambient measurements generally yield the backscatter fraction, and theoretical calculations of scattering phase functions often yield the asymmetry parameter. Therefore, simple analytical relationships and parameterizations relating these three parameters are very valuable for radiative transfer calculations. Here, we review published parameterizations, mostly based on the Henyey-Greenstein phase function, and evaluate their goodness and range of validity. In addition, we give new parameterizations that are valid over the full range of backscatter fractions that are possibly encountered in the ambient atmosphere (i.e., 0 to 0.5).

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“…The moderate correlation between CO and BC is noticed were influenced by both the emissions from local activities and transport sector over the observation site. As suggested by previous studies (Kalluri et al, 2020b;Gopal et al, 2014; 2017) the long range transport sector could be an important source of absorbing aerosols (except monsoon) over the measuremt location.…”

Section: Relation Of Bc and Comentioning

confidence: 55%

Diurnal, seasonal, and vertical distribution of carbon monoxide levels and their potential sources over a semi-arid region, India

Busa

Gugamsetty

Kalluri

et al. 2022

Atm.

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The present study focuses on the investigation of both near-surface and vertical variability of carbon monoxide (CO) concentrations and their potential sources obtained from both in situ and satellite Measurements of Pollution in the Troposphere (MOPITT) over a semiarid region (Anantapur, India) from January 2016 to December 2017. The diurnal variation of CO shows sharp morning (07:00-09:00 LT) and evening (07:00-09:00 LT) peaks associated to local anthropogenic activities as well as the impact of the mixed layer height, and low concentrations during daytime (12:00-15:00 LT). The low levels during afternoon hours may be due to the increase of the mixed layer height and the decrease of anthropogenic sources. The seasonal mean CO showed no obvious variation, with highest levels observed in winter (329 ± 52 ppbv), followed by the pre-monsoon (327 ± 57 ppbv), post-monsoon (234 ± 36 ppbv) and monsoon (192 ± 22 ppbv). The high levels of CO during the winter are attributed to increased emissions from anthropogenic sources and a shallow mixed layer height. The vertical distribution of CO showed secondary peaks at high-pressure levels (300-200 hPa) during winter, pre-monsoon, and post-monsoon, which indicates CO transport from different source regions. These findings are reasonably confirmed through the air mass Concentrated Weighted Trajectory (CWT) analysis obtained from the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model. This study suggests that except for the monsoon, air masses transported from Indo-Gangetic Basin region also contribute to the enhancement of CO concentrations at the receptor site.

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In-situ measurements of atmospheric aerosols by using Integrating Nephelometer over a semi-arid station, southern India

Cited by 35 publications

References 40 publications

Applicability of benchtop multi-wavelength polar photometers to off-line measurements of the Multi-Angle Absorption Photometer (MAAP) samples

Applicability of benchtop multi-wavelength polar photometers to off-line measurements of the Multi-Angle Absorption Photometer (MAAP) samples

Parameterization of the Aerosol Upscatter Fraction as Function of the Backscatter Fraction and Their Relationships to the Asymmetry Parameter for Radiative Transfer Calculations

Diurnal, seasonal, and vertical distribution of carbon monoxide levels and their potential sources over a semi-arid region, India

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