Journal articles on the topic 'Measurement of aerosols'
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1
Zheng, Xiaojian, Baike Xi, Xiquan Dong, Timothy Logan, Yuan Wang, and Peng Wu. "Investigation of aerosol–cloud interactions under different absorptive aerosol regimes using Atmospheric Radiation Measurement (ARM) southern Great Plains (SGP) ground-based measurements." Atmospheric Chemistry and Physics 20, no. 6 (March 24, 2020): 3483–501. http://dx.doi.org/10.5194/acp-20-3483-2020.
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Abstract. The aerosol indirect effect on cloud microphysical and radiative properties is one of the largest uncertainties in climate simulations. In order to investigate the aerosol–cloud interactions, a total of 16 low-level stratus cloud cases under daytime coupled boundary-layer conditions are selected over the southern Great Plains (SGP) region of the United States. The physicochemical properties of aerosols and their impacts on cloud microphysical properties are examined using data collected from the Department of Energy Atmospheric Radiation Measurement (ARM) facility at the SGP site. The aerosol–cloud interaction index (ACIr) is used to quantify the aerosol impacts with respect to cloud-droplet effective radius. The mean value of ACIr calculated from all selected samples is 0.145±0.05 and ranges from 0.09 to 0.24 at a range of cloud liquid water paths (LWPs; LWP=20–300 g m−2). The magnitude of ACIr decreases with an increasing LWP, which suggests a diminished cloud microphysical response to aerosol loading, presumably due to enhanced condensational growth processes and enlarged particle sizes. The impact of aerosols with different light-absorbing abilities on the sensitivity of cloud microphysical responses is also investigated. In the presence of weak light-absorbing aerosols, the low-level clouds feature a higher number concentration of cloud condensation nuclei (NCCN) and smaller effective radii (re), while the opposite is true for strong light-absorbing aerosols. Furthermore, the mean activation ratio of aerosols to CCN (NCCN∕Na) for weakly (strongly) absorbing aerosols is 0.54 (0.45), owing to the aerosol microphysical effects, particularly the different aerosol compositions inferred by their absorptive properties. In terms of the sensitivity of cloud-droplet number concentration (Nd) to NCCN, the fraction of CCN that converted to cloud droplets (Nd∕NCCN) for the weakly (strongly) absorptive regime is 0.69 (0.54). The measured ACIr values in the weakly absorptive regime are relatively higher, indicating that clouds have greater microphysical responses to aerosols, owing to the favorable thermodynamic condition. The reduced ACIr values in the strongly absorptive regime are due to the cloud-layer heating effect induced by strong light-absorbing aerosols. Consequently, we expect larger shortwave radiative cooling effects from clouds in the weakly absorptive regime than those in the strongly absorptive regime.
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Uin, Janek, Allison C. Aiken, Manvendra K. Dubey, Chongai Kuang, Mikhail Pekour, Cynthia Salwen, Arthur J. Sedlacek, et al. "Atmospheric Radiation Measurement (ARM) Aerosol Observing Systems (AOS) for Surface-Based In Situ Atmospheric Aerosol and Trace Gas Measurements." Journal of Atmospheric and Oceanic Technology 36, no. 12 (December 2019): 2429–47. http://dx.doi.org/10.1175/jtech-d-19-0077.1.
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AbstractAerosols alter Earth’s radiative budget both directly and indirectly through interaction with clouds. Continuous observations are required to reduce the uncertainties in climate models associated with atmospheric processing and the interactions between aerosols and clouds. Field observations of aerosols are a central component of the Atmospheric Radiation Measurement (ARM) Facility’s global measurements. The ARM mission goal is to “provide the climate research community with strategically located in situ and remote sensing observatories designed to improve the understanding and representation, in climate and earth system models, of clouds and aerosols as well as their interactions and coupling with the Earth’s surface.” Since 1996, ARM has met this goal by operating Aerosol Observing Systems (AOS) for in situ measurement of aerosols. Currently the five ARM AOSs are the most comprehensive field deployable aerosol systems in the United States. The AOS suite includes seven measurement classes: number concentration, size distribution, chemical composition, radiative and optical properties, hygroscopicity, trace gases, and supporting meteorological conditions. AOSs are designed as standardized measurement platforms to enable intercomparison across the ARM Facility for regional process studies within a global context. The instrumentation and measurement capabilities of the ARM AOSs, along with a history of their design and field deployments are presented here.
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Lee, Jeonghoon, and Hans Moosmüller. "Measurement of Light Absorbing Aerosols with Folded-Jamin Photothermal Interferometry." Sensors 20, no. 9 (May 4, 2020): 2615. http://dx.doi.org/10.3390/s20092615.
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In this study, a photothermal interferometer was developed, based on a folded-Jamin polarization instrument with refractive-index sensitive configuration, in order to characterize light-absorbing aerosols. The feasibility of our interferometric technique was demonstrated by performing photothermal spectroscopy characterizing spark-generated black carbon particles with atmospherically relevant concentrations and atmospheric aerosols in a metropolitan area. The sensitivity of this interferometric system for both laboratory-generated aerosols and atmospheric aerosols was ~ 1 (μg/m3)/μV, which is sufficient for the monitoring of black carbon aerosol in urban areas.
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Gyawali, M., W. P. Arnott, R. A. Zaveri, C. Song, H. Moosmüller, L. Liu, M. I. Mishchenko, et al. "Photoacoustic optical properties at UV, VIS, and near IR wavelengths for laboratory generated and winter time ambient urban aerosols." Atmospheric Chemistry and Physics 12, no. 5 (March 8, 2012): 2587–601. http://dx.doi.org/10.5194/acp-12-2587-2012.
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Abstract. We present the laboratory and ambient photoacoustic (PA) measurement of aerosol light absorption coefficients at ultraviolet wavelength (i.e., 355 nm) and compare with measurements at 405, 532, 870, and 1047 nm. Simultaneous measurements of aerosol light scattering coefficients were achieved by the integrating reciprocal nephelometer within the PA's acoustic resonator. Absorption and scattering measurements were carried out for various laboratory-generated aerosols, including salt, incense, and kerosene soot to evaluate the instrument calibration and gain insight on the spectral dependence of aerosol light absorption and scattering. Ambient measurements were obtained in Reno, Nevada, between 18 December 2009 and 18 January 2010. The measurement period included days with and without strong ground level temperature inversions, corresponding to highly polluted (freshly emitted aerosols) and relatively clean (aged aerosols) conditions. Particulate matter (PM) concentrations were measured and analyzed with other tracers of traffic emissions. The temperature inversion episodes caused very high concentration of PM2.5 and PM10 (particulate matter with aerodynamic diameters less than 2.5 μm and 10 μm, respectively) and gaseous pollutants: carbon monoxide (CO), nitric oxide (NO), and nitrogen dioxide (NO2). The diurnal change of absorption and scattering coefficients during the polluted (inversion) days increased approximately by a factor of two for all wavelengths compared to the clean days. The spectral variation in aerosol absorption coefficients indicated a significant amount of absorbing aerosol from traffic emissions and residential wood burning. The analysis of single scattering albedo (SSA), Ångström exponent of absorption (AEA), and Ångström exponent of scattering (AES) for clean and polluted days provides evidences that the aerosol aging and coating process is suppressed by strong temperature inversion under cloudy conditions. In general, measured UV absorption coefficients were found to be much larger for biomass burning aerosol than for typical ambient aerosols.
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Koropchak, John A., and D. H. Winn. "Fundamental Characteristics of Thermospray Aerosols and Sample Introduction for Atomic Spectrometry." Applied Spectroscopy 41, no. 8 (November 1987): 1311–18. http://dx.doi.org/10.1366/0003702874447338.
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Sample introduction to inductively coupled plasma atomic emission using thermospray nebulization is studied at a fundamental level. Optimum signals and signal-to-noise ratios result from thermospray operation at temperatures which coincide with highest analyte transport (>20%). High transport levels are maintained at sample flow rates of up to 3 mL/min. On the basis of comparison with analyte transport measurements for a pneumatic nebulizer (1.5%), signal increases are less than anticipated. Measurement of primary thermospray aerosols, using Fraunhofer diffraction, indicates that the enhanced transport results from decreased particle sizes for thermospray aerosols compared with pneumatic aerosols. Solvent is more rapidly vaporized from hot thermospray aerosols, further increasing the disparity in particle sizes. On the basis of aerosol particle size data, a conceptual model for aerosol generation, which is similar to pneumatic processes, is developed for thermospray. Trends for further improvements in thermospray aerosol production are predicted.
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Bian, Yuxuan, Chunsheng Zhao, Wanyun Xu, Gang Zhao, Jiangchuan Tao, and Ye Kuang. "Development and validation of a CCD-laser aerosol detective system for measuring the ambient aerosol phase function." Atmospheric Measurement Techniques 10, no. 6 (June 27, 2017): 2313–22. http://dx.doi.org/10.5194/amt-10-2313-2017.
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Abstract. Aerosol phase function represents the angular scattering property of aerosols, which is crucial for understanding the climate effects of aerosols that have been identified as one of the largest uncertainties in the evaluation of radiative forcing. So far, there is a lack of instruments with which to measure the aerosol phase function directly and accurately in laboratory studies and in situ measurements. A portable instrument with high angular range and resolution has been developed for the measurement of the phase function of ambient aerosols in this study. The charge-coupled device-laser aerosol detective system (CCD-LADS) measures the aerosol phase function both across a relatively wide angular range of 10–170° and at a high resolution of 0.1°. The system includes a continuous laser, two charge-coupled device cameras and the corresponding fisheye lenses. The CCD-LADS was validated by both a laboratory study and a field measurement. The comparison between the aerosol phase function retrieved from CCD-LADS and Mie-scattering model shows good agreement. Compared with the TSI polar nephelometer, CCD-LADS has the advantages of wider detection range and better stability.
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von Savigny, Christian, and Christoph G. Hoffmann. "Issues related to the retrieval of stratospheric-aerosol particle size information based on optical measurements." Atmospheric Measurement Techniques 13, no. 4 (April 16, 2020): 1909–20. http://dx.doi.org/10.5194/amt-13-1909-2020.
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Abstract. Stratospheric-sulfate aerosols play an important role in the physics and chemistry of the atmosphere. The radiative and chemical effects of stratospheric-sulfate aerosols depend critically on the aerosol particle size distribution and its variability. Despite extensive research spanning several decades, the scientific understanding of the particle size distribution of stratospheric aerosols is still incomplete. Particle size estimates (often represented by the median radius of an assumed monomodal log-normal distribution with a fixed width or by the effective radius) reported in different studies cover a wide range, even under background stratospheric conditions, and particle size estimates retrieved from satellite solar-occultation measurements in the optical spectral range show a tendency to be systematically larger than retrievals based on other optical methods. In this contribution we suggest a potential reason for these systematic differences. Differences between the actual aerosol particle size distribution and the size distribution function assumed for aerosol size retrievals may lead to systematic differences in retrieved aerosol size estimates. We demonstrate that these systematic differences may differ significantly for different measurement techniques, which is related to the different sensitivities of these measurement techniques to specific parts of the aerosol particle population. In particular, stratospheric-aerosol size retrievals based on solar-occultation observations may yield systematically larger particle size estimates (median or effective radii) compared to, e.g., lidar backscatter measurements. Aerosol concentration, on the other hand, may be systematically smaller in retrievals based on occultation measurements compared to lidar measurements. The results indicate that stratospheric-aerosol size retrievals based on occultation or lidar measurements have to be interpreted with caution, as long as the actual aerosol particle size distribution is not well known.
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Yu, H., Y. J. Kaufman, M. Chin, G. Feingold, L. A. Remer, T. L. Anderson, Y. Balkanski, et al. "A review of measurement-based assessment of aerosol direct radiative effect and forcing." Atmospheric Chemistry and Physics Discussions 5, no. 4 (August 30, 2005): 7647–768. http://dx.doi.org/10.5194/acpd-5-7647-2005.
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Abstract. Aerosols affect the Earth's energy budget ''directly'' by scattering and absorbing radiation and ''indirectly'' by acting as cloud condensation nuclei and, thereby, affecting cloud properties. However, large uncertainties exist in current estimates of aerosol forcing because of incomplete knowledge concerning the distribution and the physical and chemical properties of aerosols as well as aerosol-cloud interactions. In recent years, a great deal of effort has gone into improving measurements and datasets. It is thus feasible to shift the estimates of aerosol forcing from largely model-based to increasingly measurement-based. Here we assess the aerosol optical depth, direct radiative effect (DRE) by natural and anthropogenic aerosols, and direct climate forcing (DCF) by anthropogenic aerosols, focusing on satellite and ground-based measurements supplemented by global chemical transport model (CTM) simulations. The multi-spectral MODIS measures global distributions of aerosol optical thickness (τ) on a daily scale, with a high accuracy of ±0.03±0.05τ over ocean. The annual average τ is about 0.14 over global ocean, of which about 21% is contributed by human activities, as determined by MODIS fine-mode fraction. The multi-angle MISR derives an annual average AOT of 0.23 over global land with an uncertainty of ~20% or ± 0.05. These high-accuracy aerosol products and broadband flux measurements from CERES make it feasible to obtain observational constraints for the aerosol direct effect, especially over global ocean. A number of measurement-based approaches estimate the clear-sky DRE (on solar radiation) at the top-of-atmosphere (TOA) to be about −5.5±0.2 Wm−2 (median ± standard error) over global ocean. Accounting for thin cirrus contamination of the satellite derived aerosol field will reduce the TOA DRE to −5.0 Wm−2. Because of a lack of measurements of aerosol absorption and difficulty in characterizing land surface reflection, estimates of DRE over land and at the ocean surface are currently realized through a combination of satellite retrievals, surface measurements, and model simulations, and are less constrained. Over the ocean surface, the DRE is estimated to be −8.8±0.4 Wm-2. Over land, an integration of satellite retrievals and model simulations derives a DRE of −4.9±0.7 Wm−2 and −11.8±1.9 Wm−2 at the TOA and surface, respectively. CTM simulations derive a wide range of DRE estimates that on average are smaller than the measurement-based DRE by about 30–40%, even after accounting for thin cirrus and cloud contamination. Despite these achievements, a number of issues remain open and more efforts are required to address them. Current estimates of the aerosol direct effect over land are poorly constrained. Uncertainties of DRE estimates are also larger on regional scales than on a global scale and large discrepancies exist between different approaches. The characterization of aerosol absorption and vertical distribution remains challenging. The aerosol direct effect in the thermal infrared range and under cloudy condition remains relatively unexplored and quite uncertain, because of a lack of global systematic aerosol vertical profile measurements. A coordinated research strategy needs to be developed for integration and assimilation of satellite measurements into models to constrain model simulations. Hopefully, enhanced measurement capabilities in the next few years and high-level scientific cooperation, will further advance our knowledge.
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Xie, Hailing, Zhien Wang, Tao Luo, Kang Yang, Damao Zhang, Tian Zhou, Xueling Yang, Xiaohong Liu, and Qiang Fu. "Seasonal Variation of Dust Aerosol Vertical Distribution in Arctic Based on Polarized Micropulse Lidar Measurement." Remote Sensing 14, no. 21 (November 4, 2022): 5581. http://dx.doi.org/10.3390/rs14215581.
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This study investigates the seasonal variation of dust aerosol vertical distribution using polarized Micropulse lidar (MPL) measurements at the Atmospheric Radiation Measurement (ARM) North Slope of Alaska (NSA) observatory from January 2013 to September 2017. For the first time, multi-year aerosol backscatter coefficients are retrieved at the ARM NSA site from MPL measurements and are consistent with co-located high spectral resolution lidar (HSRL) measurements. The high-quality aerosol backscatter coefficient retrievals are used to derive the particle depolarization ratio (PDR) at the wavelength of 532 nm, which is used to identify the presence of dust aerosols. The annual cycles of the vertical distributions of dust backscatter coefficient and PDR and dust aerosol optical depth (DAOD) show that aerosol loading has a maximum in late winter and early spring but a minimum in late summer and early autumn. Vertically, dust aerosol occurs in the entire troposphere in spring and winter and in the low and middle troposphere in summer and autumn. Because dust aerosols are effective ice nuclei, the seasonality of dust aerosol vertical distribution has important implications for the Arctic climate through aerosol–cloud–radiation interactions, primarily through impacting mixed-phase cloud processes.
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Gyawali, M., W. P. Arnott, R. A. Zaveri, C. Song, H. Moosmüller, L. Liu, M. I. Mishchenko, et al. "Photoacoustic optical properties at UV, VIS, and near IR wavelengths for laboratory generated and winter time ambient urban aerosols." Atmospheric Chemistry and Physics Discussions 11, no. 9 (September 8, 2011): 25063–98. http://dx.doi.org/10.5194/acpd-11-25063-2011.
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Abstract. We present the first laboratory and ambient photoacoustic (PA) measurement of aerosol light absorption coefficients at ultraviolet (UV) wavelength (i.e. 355 nm) and compare with measurements at 405, 532, 870, and 1047 nm. Simultaneous measurements of aerosol light scattering coefficients were achieved by the integrating reciprocal nephelometer within the PA's acoustic resonator. Absorption and scattering measurements were carried out for various laboratory-generated aerosols, including salt, incense, and kerosene soot to evaluate the instrument calibration and gain insight on the spectral dependence of aerosol light absorption and scattering. Exact T-matrix method calculations were used to model the absorption and scattering characteristics of fractal-like agglomerates of different compactness and varying number of monomers. With these calculations, we attempted to estimate the number of monomers and fractal dimension of laboratory generated kerosene soot. Ambient measurements were obtained in Reno, Nevada, between 18 December 2009, and 18 January 2010. The measurement period included days with and without strong ground level temperature inversions, corresponding to highly polluted (freshly emitted aerosols) and relatively clean (aged aerosols) conditions. Particulate matter (PM) concentrations were measured and analyzed with other tracers of traffic emissions. The temperature inversion episodes caused very high concentration of PM2.5 and PM10 (particulate matter with aerodynamic diameters less than 2.5 μm and 10 μm, respectively) and gaseous pollutants: carbon monoxide (CO), nitric oxide (NO), and nitrogen dioxide (NO2). The diurnal change of absorption and scattering coefficients during the polluted (inversion) days increased approximately by a factor of two for all wavelengths compared to the clean days. The spectral variation in aerosol absorption coefficients indicated a significant amount of absorbing aerosol from traffic emissions and residential wood burning. The analysis of single scattering albedo (SSA), Ångström exponent of absorption (AEA), and Ångström exponent of scattering (AES) for clean and polluted days provides evidences that the aerosol aging and coating process is suppressed by strong temperature inversion under cloudy conditions. In general, measured UV absorption coefficients were found to be much larger for biomass burning aerosol than for typical ambient aerosols.
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Chtioui, H., F. B. Mansour, S. Elouragini, and P. H. Flamant. "Remote sensing of cirrus clouds and aerosols by a sun photometer in Tunisia." Atmospheric Chemistry and Physics Discussions 6, no. 2 (April 21, 2006): 3321–35. http://dx.doi.org/10.5194/acpd-6-3321-2006.
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Abstract. Some ground based measurements of solar radiation by using a sun photometer, have been conducted in Tunisia during the period of November 2000–February 2002. Five key measurement sites were selected: Three Sites (Tunis, Sousse, Gabes) are located on the Mediterranean coast and Two sites (Gafsa, Tozeur) on the boarder of Sahara. Over a total of 149 measurement days, 21 days are identified as clear sky, 114 days as Cirrus clouds and 14 days as aerosols. Aerosols and Cirrus clouds Optical Thickness (AOT) are derived from photometric measurements at 532 nm wavelength. Spatial and temporal variabilities of AOT are presented and discussed in this paper. Cirrus clouds were frequently observed at Gafsa and Tozeur where saharan aerosol events are expected to be more frequent than cirrus clouds. The mediterranean sea and saharan aerosols are suspected to have the main role in cirrus clouds formation, by providing water vapor and high concentrations of cloud condensation and ice forming nuclei.
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Xie, Zhibo, Jiaoshi Zhang, Huaqiao Gui, Yang Liu, Bo Yang, Haosheng Dai, Hang Xiao, Douguo Zhang, Da-Ren Chen, and Jianguo Liu. "Atmospheric nanoparticles hygroscopic growth measurement by a combined surface plasmon resonance microscope and hygroscopic tandem differential mobility analyzer." Atmospheric Chemistry and Physics 23, no. 3 (February 9, 2023): 2079–88. http://dx.doi.org/10.5194/acp-23-2079-2023.
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Abstract. The hygroscopic growth of atmospheric aerosols plays an important role in regional radiation, cloud formation, and hence climate. Aerosol hygroscopic growth is often characterized by hygroscopic tandem differential mobility analyzers (HTDMAs), and Xie et al. (2020) recently demonstrated that hygroscopic growth measurements of a single particle are possible using a surface plasmon resonance microscope-azimuthal rotation illumination (SPRM-ARI). The hygroscopic properties of ambient aerosols are not uniform and often exhibit large relative humidity (RH) and size variabilities due to different chemical compositions and mixing states. To better understand the contribution of different aerosol components and establish a link between the apparent hygroscopic properties of single particles and bulk aerosols, we conduct combined hygroscopic growth measurements using a SPRM-ARI and an HTDMA as a case study to prove the concept (experimental information: 100–200 nm, during noontime on 28 September 2021 and 22 March 2022 in Hefei, China). According to the distinct hygroscopic growth behavior from single-particle probing using a SPRM-ARI, the individual particles can be classified into three categories defined as non-hygroscopic (NH), less hygroscopic (LH), and more hygroscopic (MH). The mean growth factor (GF) of the three categories can be utilized to reproduce the GF distribution obtained from the HTDMA measurement. The chemical compositions of individual particles from the three categories are identified to be organic carbon (OC), soot (mainly elemental carbon), fly ash, and secondary aerosols (mainly OC and sulfate), using scanning electron microscopy (SEM) with an energy-dispersive spectrometer (EDS). The coupled SPRM–HTDMA measurement suggests a size-dependent variation of aerosol chemical components, i.e., an increase of OC fraction with increasing particle sizes, which agrees reasonably well with the chemical compositions from collected aerosol samples. This likely links the hygroscopic properties of individual particles to their bulk hygroscopic growth and chemical composition.
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Li, Z. Q., H. Xu, K. T. Li, D. H. Li, Y. S. Xie, L. Li, Y. Zhang, et al. "Comprehensive Study of Optical, Physical, Chemical, and Radiative Properties of Total Columnar Atmospheric Aerosols over China: An Overview of Sun–Sky Radiometer Observation Network (SONET) Measurements." Bulletin of the American Meteorological Society 99, no. 4 (April 2018): 739–55. http://dx.doi.org/10.1175/bams-d-17-0133.1.
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AbstractAn overview of Sun–Sky Radiometer Observation Network (SONET) measurements in China is presented. Based on observations at 16 distributed SONET sites in China, atmospheric aerosol parameters are acquired via standardization processes of operational measurement, maintenance, calibration, inversion, and quality control implemented since 2010. A climatology study is performed focusing on total columnar atmospheric aerosol characteristics, including optical (aerosol optical depth, ÅngstrÖm exponent, fine-mode fraction, single-scattering albedo), physical (volume particle size distribution), chemical composition (black carbon; brown carbon; fine-mode scattering component, coarse-mode component; and aerosol water), and radiative properties (aerosol radiative forcing and efficiency). Data analyses show that aerosol optical depth is low in the west but high in the east of China. Aerosol composition also shows significant spatial and temporal variations, leading to noticeable diversities in optical and physical property patterns. In west and north China, aerosols are generally affected by dust particles, while monsoon climate and human activities impose remarkable influences on aerosols in east and south China. Aerosols in China exhibit strong light-scattering capability and result in significant radiative cooling effects.
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Yu, H., Y. J. Kaufman, M. Chin, G. Feingold, L. A. Remer, T. L. Anderson, Y. Balkanski, et al. "A review of measurement-based assessments of the aerosol direct radiative effect and forcing." Atmospheric Chemistry and Physics 6, no. 3 (February 27, 2006): 613–66. http://dx.doi.org/10.5194/acp-6-613-2006.
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Abstract. Aerosols affect the Earth's energy budget directly by scattering and absorbing radiation and indirectly by acting as cloud condensation nuclei and, thereby, affecting cloud properties. However, large uncertainties exist in current estimates of aerosol forcing because of incomplete knowledge concerning the distribution and the physical and chemical properties of aerosols as well as aerosol-cloud interactions. In recent years, a great deal of effort has gone into improving measurements and datasets. It is thus feasible to shift the estimates of aerosol forcing from largely model-based to increasingly measurement-based. Our goal is to assess current observational capabilities and identify uncertainties in the aerosol direct forcing through comparisons of different methods with independent sources of uncertainties. Here we assess the aerosol optical depth (τ), direct radiative effect (DRE) by natural and anthropogenic aerosols, and direct climate forcing (DCF) by anthropogenic aerosols, focusing on satellite and ground-based measurements supplemented by global chemical transport model (CTM) simulations. The multi-spectral MODIS measures global distributions of aerosol optical depth (τ) on a daily scale, with a high accuracy of ±0.03±0.05τ over ocean. The annual average τ is about 0.14 over global ocean, of which about 21%±7% is contributed by human activities, as estimated by MODIS fine-mode fraction. The multi-angle MISR derives an annual average AOD of 0.23 over global land with an uncertainty of ~20% or ±0.05. These high-accuracy aerosol products and broadband flux measurements from CERES make it feasible to obtain observational constraints for the aerosol direct effect, especially over global the ocean. A number of measurement-based approaches estimate the clear-sky DRE (on solar radiation) at the top-of-atmosphere (TOA) to be about -5.5±0.2 Wm-2 (median ± standard error from various methods) over the global ocean. Accounting for thin cirrus contamination of the satellite derived aerosol field will reduce the TOA DRE to -5.0 Wm-2. Because of a lack of measurements of aerosol absorption and difficulty in characterizing land surface reflection, estimates of DRE over land and at the ocean surface are currently realized through a combination of satellite retrievals, surface measurements, and model simulations, and are less constrained. Over the oceans the surface DRE is estimated to be -8.8±0.7 Wm-2. Over land, an integration of satellite retrievals and model simulations derives a DRE of -4.9±0.7 Wm-2 and -11.8±1.9 Wm-2 at the TOA and surface, respectively. CTM simulations derive a wide range of DRE estimates that on average are smaller than the measurement-based DRE by about 30-40%, even after accounting for thin cirrus and cloud contamination. A number of issues remain. Current estimates of the aerosol direct effect over land are poorly constrained. Uncertainties of DRE estimates are also larger on regional scales than on a global scale and large discrepancies exist between different approaches. The characterization of aerosol absorption and vertical distribution remains challenging. The aerosol direct effect in the thermal infrared range and in cloudy conditions remains relatively unexplored and quite uncertain, because of a lack of global systematic aerosol vertical profile measurements. A coordinated research strategy needs to be developed for integration and assimilation of satellite measurements into models to constrain model simulations. Enhanced measurement capabilities in the next few years and high-level scientific cooperation will further advance our knowledge.
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Case, John A., and Robert W. Smith. "Low frequency photoacoustic optical absorption measurement of aerosols." Journal of the Acoustical Society of America 152, no. 4 (October 2022): A261. http://dx.doi.org/10.1121/10.0016206.
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Atmospheric optical absorption, including the contribution from aerosols, is important in modeling optical propagation and for climate research. An open-celled photoacoustic aerosol sensing system was developed to operate at 150 Hz for measurement of absorption aerosols up to 3 microns in diameter with the design goal to achieve a sensitivity adequate to measure an absorption corresponding to a 1/e optical absorption length of 1 Mm. The advantage of a photoacoustic system is that it measures optical absorption only and is not sensitive to optical extinction due to scattering at low absorption levels. The system was calibrated against an existing black carbon absorption measurement unit made by Droplet Measurement Technologies, which operates at a shorter optical wavelength and higher acoustic frequency. With previous work focusing on measuring optical absorption by black carbon aerosols [J.A. Case and R.W. Smith,182nd meeting of the Acoustical Society of America in Denver, CO (5aPA)], this work covers measuring absorption by wet salt solutions of similar salt concentration to that oceanic aerosols. Experiments with the current system showed an anomalous photoacoustic signal appearing in the absence of any aerosols. Several solutions to eliminating the unwanted signal from the desired measurement are proposed and tested.
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Moorchilot, Vishnu S., Usha K. Aravind, Sunil Paul M. Menacherry, and Charuvila T. Aravindakumar. "Single-Particle Analysis of Atmospheric Aerosols: Applications of Raman Spectroscopy." Atmosphere 13, no. 11 (October 28, 2022): 1779. http://dx.doi.org/10.3390/atmos13111779.
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Atmospheric aerosols, produced as a consequence of different anthropogenic and natural processes, impart significant control over the global energy budget, climate, and human–environmental health. Their size varies across the nano–micrometer scale. Based on their origin, they may be classified into primary or secondary aerosols. Biomass burning, incomplete combustion of fossil fuels, volcanic eruptions, and traffic-related and wind-driven suspensions contribute to primary aerosol emissions. In contrast, gas-to-particle conversion within the atmosphere leads to secondary particle production. The study of atmospheric aerosols is vital to the field of atmospheric research. The dynamic nature (highly variable concentration composition and size with space and time) of aerosols makes them difficult to investigate. Today, aerosol research involves the application of various spectrometric and spectroscopic techniques. The single-particle analysis of aerosols is yet a challenge. In this review, the merits and demerits of various offline and online techniques used for aerosol research are discussed in a nutshell. Mass spectrometric techniques fail in distinguishing certain species. However, Raman spectroscopy’s emergence for the compositional analysis of aerosols resolves most of the present characterization challenges. This review focuses on Raman spectroscopy applications, the merits of this technique, and its immense scope for the measurement of various types of aerosols and their properties. Surface-enhanced Raman spectroscopy (SERS) has an advantage over conventional micro-Raman spectroscopy (MRS). The review depicts the dominance of SERS, specifically in the context of the measurement of ambient atmospheric aerosols. This review discusses two important components, namely laboratory simulation and ambient aerosol studies.
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Sinclair, David. "Measurement of Nanometer Aerosols." Aerosol Science and Technology 5, no. 2 (January 1986): 187–204. http://dx.doi.org/10.1080/02786828608959087.
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Cheng, Yueming, Tie Dai, Jiming Li, and Guangyu Shi. "Measurement Report: Determination of aerosol vertical features on different timescales over East Asia based on CATS aerosol products." Atmospheric Chemistry and Physics 20, no. 23 (December 10, 2020): 15307–22. http://dx.doi.org/10.5194/acp-20-15307-2020.
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Abstract. The Cloud-Aerosol Transport System (CATS) lidar, on board the International Space Station (ISS), provides a new opportunity for studying aerosol vertical distributions, especially the diurnal variations, from space observations. In this study, we investigate the seasonal variations and diurnal cycles in the vertical aerosol extinction coefficients (AECs) over East Asia by taking advantage of 32 months of continuous and uniform aerosol measurements from the CATS lidar. Over the Tibetan Plateau, a belt of AECs at approximately 6 km between 30 and 38∘ N persistently exists in all seasons with an obvious seasonal variation. In summer, the aerosols at 6 km are identified as a mixture of both anthropogenic aerosols transported from India and coarse dust particles from Asian dust sources. In addition, the high AECs up to 8 km in summer over the Tibetan Plateau are caused by smoke aerosols from thermal dynamic processes. In fall and winter, the northern slope of the plateau is continuously influenced by both dust aerosols and polluted aerosols transported upslope from cities located at lower elevations in northwestern Asia. The diurnal variation in AECs in North China is mainly related to the diurnal variations in the transported dust and local polluted aerosols. Below 2 km, the AEC profiles in North China at 06:00 and 12:00 CST (China standard time) are significantly higher than those at 00:00 and 18:00 CST, reaching a maximum at midday. The aerosol vertical profiles over the Tarim Desert region in summer have obvious diurnal variations, and the AECs at 12:00 and 18:00 CST are significantly higher than those at 00:00 and 06:00 CST, which are induced by the strong diurnal variations in near-surface wind speeds. In addition, the peak in the AEC profiles has a significant seasonal variation, which is mainly determined by the boundary layer height.
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Leitão, J., A. Richter, M. Vrekoussis, A. Kokhanovsky, Q. J. Zhang, M. Beekmann, and J. P. Burrows. "On the improvement of NO<sub>2</sub> satellite retrievals – aerosol impact on the airmass factors." Atmospheric Measurement Techniques Discussions 2, no. 6 (December 11, 2009): 3221–64. http://dx.doi.org/10.5194/amtd-2-3221-2009.
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Abstract. The accurate determination of nitrogen dioxide (NO2) tropospheric vertical columns from satellite measurements depends, partly, on the airmass factor (AMF) used. A sensitivity study was performed with the radiative transfer model SCIATRAN to better understand the impact of aerosols in the calculation of NO2 AMFs. This influence was studied by varying the NO2 and aerosol vertical distributions, as well as physical and optical properties of the particles. The key factors for these calculations were identified as the relation between trace gas and aerosol vertical profiles, the optical depth of the aerosol layer, and single scattering albedo. Overall it was found that aerosol mixed with the trace gas increases the measurements' sensitivity. The largest change, a factor of ~2 relative to the situation without aerosols, was found when a low layer of aerosol (600 m) was combined with a homogenous NO2 layer of 1.0 km. A layer of aerosol above the NO2 will usually reduce the sensitivity of the satellite measurement, a situation found mostly for runs with discrete elevated aerosol layers representative for long-range transport of aerosols that can generate a decrease of the AMF values of up to 70%. The use of measured aerosol profiles and modelled NO2 resulted, generally, in a much smaller changes of AMF relative to the pure Rayleigh case. Exceptions are some events of elevated layers with high aerosol optical depth that lead to a strong decrease of the AMF values. These results highlight the importance of aerosols in the retrieval of tropospheric NO2 columns from space and indicate the need for detailed information on aerosol properties and vertical distribution.
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Dougniaux, Grégoire, William Soerjady, Kelvin Ankrah, and Diane Mauclère. "Numerical Simulation of a CAM-Measured Spectra Influenced by Coarse Aerosol." Atmosphere 13, no. 12 (December 16, 2022): 2113. http://dx.doi.org/10.3390/atmos13122113.
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In nuclear facilities, the mandatory atmosphere surveillance is operated by Continuous Air Monitors. This standalone instrument is designed to measure the airborne aerosol activity concentration and to trig an alarm signal when a predetermined activity concentration is exceeded. However, a rapid resuspension event of coarse aerosol leads to a measurement error: the airborne aerosol activity concentration is over-evaluated. Prior results have shown that the coarse aerosol deposit disturbs the background evaluation for the radioactivity measurement. The interactions between radioactive aerosols (with radon daughters) and coarse non-radioactive aerosols have to be investigated by running together aerosol models and nuclear simulations. Therefore, this paper investigates different ways to represent an aerosol deposit in numerical simulations. We developed two numerical aerosol deposit models that we integrated into Geant4, a tool for the simulation of the passage of radiations through matter, and then compared these to experimental results. The simplest model was discarded, and by using the second model, we managed to correctly frame our simulation results as an experimental measurement: an aerosol has been correctly considered in a nuclear simulation. By combining theory, simulations, and experimentations on both aerosol science and nuclear physics, this research will be able to improve the comprehension of monitors’ behaviour in delicate situations and, more broadly, the filtration of aerosols using radioactivity.
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Chan, C. H., A. Y. S. Cheng, and A. Viseu. "A simplified empirical method for determination of aerosol hygroscopicity and composition." Atmospheric Chemistry and Physics Discussions 10, no. 10 (October 12, 2010): 23627–56. http://dx.doi.org/10.5194/acpd-10-23627-2010.
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Abstract. Atmospheric aerosols have substantial influence on the Earth's radiation budget, visibility, cloud formation and precipitation. The aerosol hygroscopicity and the composition of aerosols are of vital importance for solar radiation budget calculation, cloud formation mechanism, and measurement of aerosol spatiotemporal distribution through remote sensing, such as Lidar, MODIS and sun/star photometer. In this paper, hourly averaged records of humidity, visibility and aerosol concentration, conducted in Macao, P.R.C. from 1 February 2006 to 31 December 2008 (LT), are used to estimate aerosol hygroscopicity and composition with a simplified empirical method. The result of monthly variation of aerosol hygroscopicity indicates the important role of aerosol composition on optical properties, which is in agreement with the previous study. This aerosol composition pattern is also consistent with the Asiatic Monsoon pattern and vicinity, such as Hong Kong. The monthly variation of aerosol hygroscopicity and composition also shows the necessity to consider such a factor for the aerosols monitoring by remote system and aerosols forcing simulated by climate model.
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Haywood, Jim M., Steven J. Abel, Paul A. Barrett, Nicolas Bellouin, Alan Blyth, Keith N. Bower, Melissa Brooks, et al. "The CLoud–Aerosol–Radiation Interaction and Forcing: Year 2017 (CLARIFY-2017) measurement campaign." Atmospheric Chemistry and Physics 21, no. 2 (January 27, 2021): 1049–84. http://dx.doi.org/10.5194/acp-21-1049-2021.
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Abstract. The representations of clouds, aerosols, and cloud–aerosol–radiation impacts remain some of the largest uncertainties in climate change, limiting our ability to accurately reconstruct past climate and predict future climate. The south-east Atlantic is a region where high atmospheric aerosol loadings and semi-permanent stratocumulus clouds are co-located, providing an optimum region for studying the full range of aerosol–radiation and aerosol–cloud interactions and their perturbations of the Earth's radiation budget. While satellite measurements have provided some useful insights into aerosol–radiation and aerosol–cloud interactions over the region, these observations do not have the spatial and temporal resolution, nor the required level of precision to allow for a process-level assessment. Detailed measurements from high spatial and temporal resolution airborne atmospheric measurements in the region are very sparse, limiting their use in assessing the performance of aerosol modelling in numerical weather prediction and climate models. CLARIFY-2017 was a major consortium programme consisting of five principal UK universities with project partners from the UK Met Office and European- and USA-based universities and research centres involved in the complementary ORACLES, LASIC, and AEROCLO-sA projects. The aims of CLARIFY-2017 were fourfold: (1) to improve the representation and reduce uncertainty in model estimates of the direct, semi-direct, and indirect radiative effect of absorbing biomass burning aerosols; (2) to improve our knowledge and representation of the processes determining stratocumulus cloud microphysical and radiative properties and their transition to cumulus regimes; (3) to challenge, validate, and improve satellite retrievals of cloud and aerosol properties and their radiative impacts; (4) to improve the impacts of aerosols in weather and climate numerical models. This paper describes the modelling and measurement strategies central to the CLARIFY-2017 deployment of the FAAM BAe146 instrumented aircraft campaign, summarizes the flight objectives and flight patterns, and highlights some key results from our initial analyses.
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Wang, Yuan, Xiaojian Zheng, Xiquan Dong, Baike Xi, Peng Wu, Timothy Logan, and Yuk L. Yung. "Impacts of long-range transport of aerosols on marine-boundary-layer clouds in the eastern North Atlantic." Atmospheric Chemistry and Physics 20, no. 23 (December 2, 2020): 14741–55. http://dx.doi.org/10.5194/acp-20-14741-2020.
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Abstract. Vertical profiles of aerosols are inadequately observed and poorly represented in climate models, contributing to the current large uncertainty associated with aerosol–cloud interactions. The US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA) aircraft field campaign near the Azores islands provided ample observations of vertical distributions of aerosol and cloud properties. Here we utilize the in situ aircraft measurements from the ACE-ENA and ground-based remote-sensing data along with an aerosol-aware Weather Research and Forecast (WRF) model to characterize the aerosols due to long-range transport over a remote region and to assess their possible influence on marine-boundary-layer (MBL) clouds. The vertical profiles of aerosol and cloud properties measured via aircraft during the ACE-ENA campaign provide detailed information revealing the physical contact between transported aerosols and MBL clouds. The European Centre for Medium-Range Weather Forecasts Copernicus Atmosphere Monitoring Service (ECMWF-CAMS) aerosol reanalysis data can reproduce the key features of aerosol vertical profiles in the remote region. The cloud-resolving WRF sensitivity experiments with distinctive aerosol profiles suggest that the transported aerosols and MBL cloud interactions (ACIs) require not only aerosol plumes to get close to the marine-boundary-layer top but also large cloud top height variations. Based on those criteria, the observations show that the occurrence of ACIs involving the transport of aerosol over the eastern North Atlantic (ENA) is about 62 % in summer. For the case with noticeable long-range-transport aerosol effects on MBL clouds, the susceptibilities of droplet effective radius and liquid water content are −0.11 and +0.14, respectively. When varying by a similar magnitude, aerosols originating from the boundary layer exert larger microphysical influence on MBL clouds than those entrained from the free troposphere.
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Varma, R. M., S. M. Ball, T. Brauers, H. P. Dorn, U. Heitmann, R. L. Jones, U. Platt, et al. "Light extinction by secondary organic aerosol: an intercomparison of three broadband cavity spectrometers." Atmospheric Measurement Techniques 6, no. 11 (November 19, 2013): 3115–30. http://dx.doi.org/10.5194/amt-6-3115-2013.
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Abstract. Broadband optical cavity spectrometers are maturing as a technology for trace-gas detection, but only recently have they been used to retrieve the extinction coefficient of aerosols. Sensitive broadband extinction measurements allow explicit separation of gas and particle phase spectral contributions, as well as continuous spectral measurements of aerosol extinction in favourable cases. In this work, we report an intercomparison study of the aerosol extinction coefficients measured by three such instruments: a broadband cavity ring-down spectrometer (BBCRDS), a cavity-enhanced differential optical absorption spectrometer (CE-DOAS), and an incoherent broadband cavity-enhanced absorption spectrometer (IBBCEAS). Experiments were carried out in the SAPHIR atmospheric simulation chamber as part of the NO3Comp campaign to compare the measurement capabilities of NO3 and N2O5 instrumentation. Aerosol extinction coefficients between 655 and 690 nm are reported for secondary organic aerosols (SOA) formed by the NO3 oxidation of β-pinene under dry and humid conditions. Despite different measurement approaches and spectral analysis procedures, the three instruments retrieved aerosol extinction coefficients that were in close agreement. The refractive index of SOA formed from the β-pinene + NO3 reaction was 1.61, and was not measurably affected by the chamber humidity or by aging of the aerosol over several hours. This refractive index is significantly larger than SOA refractive indices observed in other studies of OH and ozone-initiated terpene oxidations, and may be caused by the large proportion of organic nitrates in the particle phase. In an experiment involving ammonium sulfate particles, the aerosol extinction coefficients as measured by IBBCEAS were found to be in reasonable agreement with those calculated using the Mie theory. The results of the study demonstrate the potential of broadband cavity spectrometers for determining the optical properties of aerosols.
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Varma, R. M., S. M. Ball, T. Brauers, H. P. Dorn, U. Heitmann, R. L. Jones, U. Platt, et al. "Light extinction by Secondary Organic Aerosol: an intercomparison of three broadband cavity spectrometers." Atmospheric Measurement Techniques Discussions 6, no. 4 (July 22, 2013): 6685–727. http://dx.doi.org/10.5194/amtd-6-6685-2013.
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Abstract. Broadband optical cavity spectrometers are maturing as a technology for trace gas detection, but only recently have they been used to retrieve the extinction coefficient of aerosols. Sensitive broadband extinction measurements allow explicit separation of gas and particle phase spectral contributions, as well as continuous spectral measurements of aerosol extinction in favourable cases. In this work, we report an intercomparison study of the aerosol extinction coefficients measured by three such instruments: a broadband cavity ring-down spectrometer (BBCRDS), a cavity-enhanced differential optical absorption spectrometer (CE-DOAS), and an incoherent broadband cavity-enhanced absorption spectrometer (IBBCEAS). Experiments were carried out in the SAPHIR atmospheric simulation chamber as part of the NO3Comp campaign to compare the measurement capabilities of NO3 and N2O5 instrumentation. Aerosol extinction coefficients between 655 and 690 nm are reported for secondary organic aerosols (SOA) formed by the NO3 oxidation of β-pinene under dry and humid conditions. Despite different measurement approaches and spectral analysis procedures, the three instruments retrieved aerosol extinction coefficients that were in close agreement. The refractive index of SOA formed from the β-pinene + NO3 reaction was 1.61, and was not measurably affected by the chamber humidity or by aging of the aerosol over several hours. This refractive index is significantly larger than SOA refractive indices observed in other studies of OH and ozone-initiated terpene oxidations, and may be caused by the large proportion of organic nitrates in the particle phase. In an experiment involving ammonium sulphate particles the aerosol extinction coefficients as measured by IBBCEAS were found to be in reasonable agreement with those calculated using Mie theory. The results of the study demonstrate the potential of broadband cavity spectrometers for determining the optical properties of aerosols.
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Kristiansen, N. I., A. Stohl, D. J. L. Olivié, B. Croft, O. A. Søvde, H. Klein, T. Christoudias, et al. "Evaluation of observed and modelled aerosol lifetimes using radioactive tracers of opportunity and an ensemble of 19 global models." Atmospheric Chemistry and Physics Discussions 15, no. 17 (September 9, 2015): 24513–85. http://dx.doi.org/10.5194/acpd-15-24513-2015.
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Abstract. Aerosols have important impacts on air quality and climate, but the processes affecting their removal from the atmosphere are not fully understood and are poorly constrained by observations. This makes modelled aerosol lifetimes uncertain. In this study, we make use of an observational constraint on aerosol lifetimes provided by radionuclide measurements and investigate the causes of differences within a set of global models. During the Fukushima Dai-Ichi nuclear power plant accident of March 2011, the radioactive isotopes cesium-137 (137Cs) and xenon-133 (133Xe) were released in large quantities. Cesium attached to particles in the ambient air, approximately according to their available aerosol surface area. 137Cs size distribution measurements taken close to the power plant suggested that accumulation-mode (AM) sulphate aerosols were the main carriers for the cesium. Hence, 137Cs can be used as a proxy tracer for the AM sulphate aerosol's fate in the atmosphere. In contrast, the noble gas 133Xe behaves almost like a passive transport tracer. Global surface measurements of the two radioactive isotopes taken over several months after the release allow the derivation of a lifetime of the carrier aerosol. We compare this to the lifetimes simulated by 19 different atmospheric transport models initialized with identical emissions of 137Cs that were assigned to an aerosol tracer with each model's default properties of AM sulphate, and 133Xe emissions that were assigned to a passive tracer. We investigate to what extent the modelled sulphate tracer can reproduce the measurements, especially with respect to the observed loss of aerosol mass with time. Modelled 37Cs and 133Xe concentrations sampled at the same location and times as station measurements allow a direct comparison between measured and modelled aerosol lifetime. The e-folding lifetime τe, calculated from station measurement data taken between two and nine weeks after the start of the emissions, is 14.3 days (95 % confidence interval 13.1–15.7 days). The equivalent modelled τe lifetimes have a large spread, varying between 4.8 and 26.7 days with a model median of 9.4 ± 2.3 days, indicating too fast removal in most models. Because sufficient measurement data were only available from about two weeks after the release, the estimated lifetimes apply to aerosols that have undergone long-range transport, i.e. not for freshly emitted aerosol. However, modelled instantaneous lifetimes show that the initial removal in the first two weeks was quicker (lifetimes between 1–5 days) due to the emissions occurring at low altitudes and co-location of the fresh plume with strong precipitation. Deviations between measured and modelled aerosol lifetimes are largest for the northernmost stations and at later time periods, suggesting that models do not transport enough of the aerosol towards the Arctic. The models underestimate passive tracer (133Xe) concentrations in the Arctic as well but to a smaller extent than for the aerosol (137Cs) tracer. This indicates that in addition to too fast aerosol removal in the models, errors in simulated atmospheric transport towards the Arctic in most models also contribute to the Arctic aerosol underestimates.
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Kristiansen, N. I., A. Stohl, D. J. L. Olivié, B. Croft, O. A. Søvde, H. Klein, T. Christoudias, et al. "Evaluation of observed and modelled aerosol lifetimes using radioactive tracers of opportunity and an ensemble of 19 global models." Atmospheric Chemistry and Physics 16, no. 5 (March 17, 2016): 3525–61. http://dx.doi.org/10.5194/acp-16-3525-2016.
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Abstract. Aerosols have important impacts on air quality and climate, but the processes affecting their removal from the atmosphere are not fully understood and are poorly constrained by observations. This makes modelled aerosol lifetimes uncertain. In this study, we make use of an observational constraint on aerosol lifetimes provided by radionuclide measurements and investigate the causes of differences within a set of global models. During the Fukushima Dai-Ichi nuclear power plant accident of March 2011, the radioactive isotopes cesium-137 (137Cs) and xenon-133 (133Xe) were released in large quantities. Cesium attached to particles in the ambient air, approximately according to their available aerosol surface area. 137Cs size distribution measurements taken close to the power plant suggested that accumulation-mode (AM) sulfate aerosols were the main carriers of cesium. Hence, 137Cs can be used as a proxy tracer for the AM sulfate aerosol's fate in the atmosphere. In contrast, the noble gas 133Xe behaves almost like a passive transport tracer. Global surface measurements of the two radioactive isotopes taken over several months after the release allow the derivation of a lifetime of the carrier aerosol. We compare this to the lifetimes simulated by 19 different atmospheric transport models initialized with identical emissions of 137Cs that were assigned to an aerosol tracer with each model's default properties of AM sulfate, and 133Xe emissions that were assigned to a passive tracer. We investigate to what extent the modelled sulfate tracer can reproduce the measurements, especially with respect to the observed loss of aerosol mass with time. Modelled 137Cs and 133Xe concentrations sampled at the same location and times as station measurements allow a direct comparison between measured and modelled aerosol lifetime. The e-folding lifetime τe, calculated from station measurement data taken between 2 and 9 weeks after the start of the emissions, is 14.3 days (95 % confidence interval 13.1–15.7 days). The equivalent modelled τe lifetimes have a large spread, varying between 4.8 and 26.7 days with a model median of 9.4 ± 2.3 days, indicating too fast a removal in most models. Because sufficient measurement data were only available from about 2 weeks after the release, the estimated lifetimes apply to aerosols that have undergone long-range transport, i.e. not for freshly emitted aerosol. However, modelled instantaneous lifetimes show that the initial removal in the first 2 weeks was quicker (lifetimes between 1 and 5 days) due to the emissions occurring at low altitudes and co-location of the fresh plume with strong precipitation. Deviations between measured and modelled aerosol lifetimes are largest for the northernmost stations and at later time periods, suggesting that models do not transport enough of the aerosol towards the Arctic. The models underestimate passive tracer (133Xe) concentrations in the Arctic as well but to a smaller extent than for the aerosol (137Cs) tracer. This indicates that in addition to too fast an aerosol removal in the models, errors in simulated atmospheric transport towards the Arctic in most models also contribute to the underestimation of the Arctic aerosol concentrations.
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Case, John A., and Robert W. Smith. "Photoacoustic optical absorption measurement of aerosols." Journal of the Acoustical Society of America 151, no. 4 (April 2022): A272. http://dx.doi.org/10.1121/10.0011305.
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Atmospheric optical absorption, including the contribution from aerosols, is important in modeling propagation of laser beams and for climate research. Photoacoustic methods have been used in the past for this purpose, as they directly measure absorption, rather than the sum of absorption and scattering. Acoustic operating frequency determines the sensed aerosol size range. The design of a windowless double-Helmholtz photoacoustic aerosol sensing system, operating at an acoustic frequency near 150 Hz, with the capability to measure an optical absorption with a 1 /e length of 1 Mm, will be presented. In this design, environmental noise limits the instrument sensitivity. To improve immunity to environmental noise with an open resonator, an aluminum acoustic enclosure was built around the system, with welded vacuum flanges for inputs and outputs. Inlet and outlet acoustic mufflers were designed to limit the in-band noise entering the measurement system. A modulated 10 W 1064 nm fiber laser was used as the excitation source, and a high-sensitivity microphone placed within the open-cell cavity was used to measure the internal photoacoustic pressure fluctuations. The system was modeled using various computational tools, including MATLAB, Simulink, and ANSYS, and then was constructed and tested. Lab measurement results will be presented.
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Meland, B. S., X. Xu, D. K. Henze, and J. Wang. "Assessing remote polarimetric measurement sensitivities to aerosol emissions using the geos-chem adjoint model." Atmospheric Measurement Techniques 6, no. 12 (December 10, 2013): 3441–57. http://dx.doi.org/10.5194/amt-6-3441-2013.
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Abstract. Uncertainties in aerosol sources, microphysical properties, and global distributions undermine efforts to evaluate the radiative impacts of atmospheric aerosols. In this work, we investigate the feasibility of using remote polarimetric measurements for constraining aerosol and aerosol precursor emissions in light of these uncertainties. A model that incorporates a radiative transfer model with forward and adjoint chemical transport models has been applied to quantify the sensitivity of the reflectance at the top of atmosphere over land to aerosol emissions and microphysical properties. A set of simulated satellite observations, one intensity based and one capable of polarimetric measurements, are used to illustrate differences in the assimilation potential between the two. It is found that the sensitivity of the polarized reflectance to aerosol and aerosol precursor emissions tends to be significantly higher than that of the intensity for cases of non-absorbing aerosols. This is true even when the polarimetric sampling scheme is spatially sparser than that of the intensity sampling. This framework allows us to quantify upper limits on the uncertainties in the aerosol microphysical properties for which a 50% change in aerosol emissions is detectable using these simulated observations. It was found that although typical current remote sensing instrumentation provides retrievals of the refractive index and effective radius with accuracies within acceptable limits to detect a 50% change in emissions, retrievals of the effective variance contain uncertainties too large to detect these changes in emissions. These results may guide new applications of polarimetric measurements to constrain aerosol sources, and thus reduce uncertainty in our broader understanding of the impacts of aerosols on climate.
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Lee, Hansol D., and Alexei V. Tivanski. "Atomic Force Microscopy: An Emerging Tool in Measuring the Phase State and Surface Tension of Individual Aerosol Particles." Annual Review of Physical Chemistry 72, no. 1 (April 20, 2021): 235–52. http://dx.doi.org/10.1146/annurev-physchem-090419-110133.
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Atmospheric aerosols are suspended particulate matter of varying composition, size, and mixing state. Challenges remain in understanding the impact of aerosols on the climate, atmosphere, and human health. The effect of aerosols depends on their physicochemical properties, such as their hygroscopicity, phase state, and surface tension. These properties are dynamic with respect to the highly variable relative humidity and temperature of the atmosphere. Thus, experimental approaches that permit the measurement of these dynamic properties are required. Such measurements also need to be performed on individual, submicrometer-, and supermicrometer-sized aerosol particles, as individual atmospheric particles from the same source can exhibit great variability in their form and function. In this context, this review focuses on the recent emergence of atomic force microscopy as an experimental tool in physical, analytical, and atmospheric chemistry that enables such measurements. Remaining challenges are noted and suggestions for future studies are offered.
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Deng, Chenjuan, Yiran Li, Chao Yan, Jin Wu, Runlong Cai, Dongbin Wang, Yongchun Liu, et al. "Measurement report: Size distributions of urban aerosols down to 1 nm from long-term measurements." Atmospheric Chemistry and Physics 22, no. 20 (October 19, 2022): 13569–80. http://dx.doi.org/10.5194/acp-22-13569-2022.
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Abstract. The size distributions of urban atmospheric aerosols convey important information on their origins and impacts. Their long-term characteristics, especially for sub-3 nm particles, are still limited. In this study, we examined the characteristics of atmospheric aerosol size distributions down to ∼1 nm based on 4-year measurements in urban Beijing. Using cluster analysis, three typical types of number size distributions were identified, i.e., daytime new particle formation (NPF) type, daytime non-NPF type, and nighttime type. Combining a power law distribution and multiple lognormal distributions can well represent the sharp concentration decrease of sub-3 nm particles with increasing size and the modal characteristics for those above 3 nm in the submicron size range. The daytime NPF type exhibits high concentrations of sub-3 nm aerosols together with other three modes. However, both the daytime non-NPF type and the nighttime type have a low abundance of sub-3 nm aerosol particles together with only two distinct modes. In urban Beijing, the concentration of H2SO4 monomer during the daytime with NPF is similar to that during the daytime without NPF, while significantly higher than that during the nighttime. The concentration of atmospheric sub-3 nm particles on NPF days has a strong seasonality while their seasonality on non-NPF days is less pronounced. In addition to NPF as the most important source, we show that vehicles can emit sub-3 nm particles as well, although their influence on the measured aerosol population strongly depends on the distance from the road.
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Creamean, Jessie M., Gijs de Boer, Hagen Telg, Fan Mei, Darielle Dexheimer, Matthew D. Shupe, Amy Solomon, and Allison McComiskey. "Assessing the vertical structure of Arctic aerosols using balloon-borne measurements." Atmospheric Chemistry and Physics 21, no. 3 (February 9, 2021): 1737–57. http://dx.doi.org/10.5194/acp-21-1737-2021.
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Abstract. The rapidly warming Arctic is sensitive to perturbations in the surface energy budget, which can be caused by clouds and aerosols. However, the interactions between clouds and aerosols are poorly quantified in the Arctic, in part due to (1) limited observations of vertical structure of aerosols relative to clouds and (2) ground-based observations often being inadequate for assessing aerosol impacts on cloud formation in the characteristically stratified Arctic atmosphere. Here, we present a novel evaluation of Arctic aerosol vertical distributions using almost 3 years' worth of tethered balloon system (TBS) measurements spanning multiple seasons. The TBS was deployed at the U.S. Department of Energy Atmospheric Radiation Measurement Program's facility at Oliktok Point, Alaska. Aerosols were examined in tandem with atmospheric stability and ground-based remote sensing of cloud macrophysical properties to specifically address the representativeness of near-surface aerosols to those at cloud base. Based on a statistical analysis of the TBS profiles, ground-based aerosol number concentrations were unequal to those at cloud base 86 % of the time. Intermittent aerosol layers were observed 63 % of the time due to poorly mixed below-cloud environments, mostly found in the spring, causing a decoupling of the surface from the cloud layer. A uniform distribution of aerosol below cloud was observed only 14 % of the time due to a well-mixed below-cloud environment, mostly during the fall. The equivalent potential temperature profiles of the below-cloud environment reflected the aerosol profile 89 % of the time, whereby a mixed or stratified below-cloud environment was observed during a uniform or layered aerosol profile, respectively. In general, a combination of aerosol sources, thermodynamic structure, and wet removal processes from clouds and precipitation likely played a key role in establishing observed aerosol vertical structures. Results such as these could be used to improve future parameterizations of aerosols and their impacts on Arctic cloud formation and radiative properties.
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Jeong, Ukkyo, Si-Chee Tsay, N. Christina Hsu, David M. Giles, John W. Cooper, Jaehwa Lee, Robert J. Swap, et al. "Simultaneous retrievals of biomass burning aerosols and trace gases from the ultraviolet to near-infrared over northern Thailand during the 2019 pre-monsoon season." Atmospheric Chemistry and Physics 22, no. 18 (September 16, 2022): 11957–86. http://dx.doi.org/10.5194/acp-22-11957-2022.
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Abstract. With the advent of spaceborne spectroradiometers in a geostationary constellation, measuring high spectral resolution ultraviolet–visible (UV-VIS) and selected near-/shortwave-infrared (NIR/SWIR) radiances can enable the probing of the life cycle of key atmospheric trace gases and aerosols at higher temporal resolutions over the globe. The UV-VIS measurements are important for retrieving several key trace gases (e.g., O3, SO2, NO2, and HCHO) and particularly for deriving aerosol characteristics (e.g., aerosol absorption and vertical profile). This study examines the merit of simultaneous retrievals of trace gases and aerosols using a ground-based spectroradiometer covering the UV-NIR to monitor their physicochemical processes and to obtain reliable aerosol information for various applications. During the 2019 pre-monsoon season over northern Thailand, we deployed a ground-based SMART–s (Spectral Measurements for Atmospheric Radiative Transfer–spectroradiometer) instrument, which is an extended-range Pandora with reliable radiometric calibration in the 330–820 nm range, to retrieve remotely sensed chemical and aerosol properties for the first time near biomass burning sources. The high spectral resolution (∼ 1.0 nm full width half maximum with ∼ 3.7 × oversampling) of sun and sky measurements from SMART–s provides several key trace gases (e.g., O3, NO2, and H2O) and aerosol properties covering the UV where significant light absorption occurs by the carbonaceous particles. During the measurement period, highly correlated total column amounts of NO2 and aerosol optical thickness (τaer) retrieved from SMART–s (correlation coefficient, R=0.74) indicated their common emissions from biomass burning events. The SMART–s retrievals of the spectral single scattering albedo (ω0) of smoke aerosols showed an abrupt decrease in the UV, which is an important parameter dictating photochemical processes in the atmosphere. The values of ω0 and column precipitable water vapor (H2O) gradually increase with the mixing of biomass burning smoke particles and higher water vapor concentrations when approaching the monsoon season. The retrieved ω0 and weighted mean radius of fine-mode aerosols from SMART–s showed positive correlations with the H2O (R=0.81 for ω0 at 330 nm and 0.56 for the volume-weighted mean radius), whereas the real part of the refractive index of fine-mode aerosol (nf) showed negative correlations (R=-0.61 at 330 nm), which suggest that aerosol aging processes including hygroscopic growth (e.g., humidification and cloud processing) can be a major factor affecting the temporal trends of aerosol optical properties. Retrieved nf and ω0 were closer to those of the water droplet (i.e., nf of about 1.33 and ω0 of about 1.0) under lower amounts of NO2 during the measurement period; considering that the NO2 amounts in the smoke may indicate the aging of the plume after emission due to its short lifetime, the tendency is also consistent with active hygroscopic processes of the aerosols over this area. Retrieved UV aerosol properties from SMART–s generally support the assumed smoke aerosol models (i.e., the spectral shape of aerosol absorption) used in NASA's current satellite algorithms, and their spectral ω0 retrievals from ground and satellites showed good agreements (R = 0.73–0.79). However, temporal and spectral variabilities in the aerosol absorption properties in the UV emphasize the importance of a realistic optical model of aerosols for further improvements in satellite retrievals.
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VINOJ, V., and S. K. SATHEESH. "Observations of aerosols from space : An overview." MAUSAM 54, no. 1 (January 18, 2022): 287–98. http://dx.doi.org/10.54302/mausam.v54i1.1513.
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Aerosols are of natural and anthropogenic (man-made) origin. Aerosols directly affect the climate by scattering and absorption of solar and terrestrial radiation and indirectly by enhancing the reflectivity of clouds by acting as cloud condensation nuclei. Estimation of effects of aerosols on climate is complicated by the fact that their chemical composition, abundance and size characteristics are highly variable both spatially and temporally. Measurement of aerosols can be in situ (direct) or remote. For mapping aerosol properties on a regional or global scale, satellite based remote sensing is the only option. For the remote sensing of surface such as ocean or land, algorithms should include atmospheric corrections to correct for the atmospheric effect to satellite measured signals. However, remote sensing of aerosol properties such as its chemical composition is still extremely difficult. In this paper, we review the investigations of aerosols using satellite data with emphasis to Indian region. Various sensors and algorithms used for the remote sensing of aerosols and future scope are also discussed.
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Osada, N., Y. Oki, H. Kanda, K. Yamasaki, and S. Shibata. "Application of a graded screen array for size measurements of radioactive aerosols in accelerator rooms." Proceedings in Radiochemistry 1, no. 1 (September 1, 2011): 251–55. http://dx.doi.org/10.1524/rcpr.2011.0044.
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Abstract A rapid measurement method for aerosol particle size is required to clarify the formation mechanism of freshly-formed radioactive aerosols in accelerator rooms. A graded screen array (GSA) method only requires brief sampling. Therefore, the GSA method is suitable for the measurement of radioactive aerosols in the accelerator rooms. In this work, a conventional GSA was applied to measure the particle size distribution of an aerosol. An influence of the radioactive gas on the GSA measurement was found. The adsorption of radioactive gases resulted in a discrepancy between the results of the GSA method and those of the diffusion battery method. An improved GSA method was developed to measure the radioactive aerosol formed in the accelerator room. The adsorption was measured by the improved GSA, and the influence of the radioactive gas was eliminated. The result of the improved GSA showed fair agreement with that of the diffusion battery system.
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Baker, Alex R., and Chan Yodle. "Measurement report: Indirect evidence for the controlling influence of acidity on the speciation of iodine in Atlantic aerosols." Atmospheric Chemistry and Physics 21, no. 17 (September 2, 2021): 13067–76. http://dx.doi.org/10.5194/acp-21-13067-2021.
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Abstract. The speciation of soluble iodine and major-ion composition were determined in size-fractionated aerosols collected during the AMT21 cruise between Avonmouth, UK, and Punta Arenas, Chile, in September–November 2011. The proportions of iodine species (iodide, iodate and soluble organic iodine (SOI)) varied markedly between size fractions and with the extent to which the samples were influenced by pollutants. In general, fine mode aerosols (< 1 µm) contained higher proportions of both iodide and SOI, while iodate was the dominant component of coarse (< 1 µm) aerosols. The highest proportions of iodate were observed in aerosols that contained (alkaline) unpolluted sea spray or mineral dust. Fine mode samples with high concentrations of acidic species (e.g. non-sea-salt sulfate) contained very little iodate and elevated proportions of iodide and SOI. These results are in agreement with modelling studies that indicate that iodate can be reduced under acidic conditions and that the resulting hypoiodous acid (HOI) can react with organic matter to produce SOI and iodide. Further work that investigates the link between iodine speciation and aerosol pH directly, as well as studies on the formation and decay of organo-iodine compounds under aerosol conditions, will be necessary before the importance of this chemistry in regulating aerosol iodine speciation can be confirmed.
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Ortega, J., A. Turnipseed, A. B. Guenther, T. G. Karl, D. A. Day, D. Gochis, J. A. Huffman, et al. "Overview of the Manitou Experimental Forest Observatory: site description and selected science results from 2008–2013." Atmospheric Chemistry and Physics Discussions 14, no. 2 (January 20, 2014): 1647–709. http://dx.doi.org/10.5194/acpd-14-1647-2014.
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Abstract. The Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen (BEACHON) project seeks to understand the feedbacks and inter-relationships between hydrology, biogenic emissions, carbon assimilation, aerosol properties, clouds and associated feedbacks within water-limited ecosystems. The Manitou Experimental Forest Observatory (MEFO) was established in 2008 by the National Center for Atmospheric Research to address many of the BEACHON research objectives, and it now provides a fixed field site with significant infrastructure. MEFO is a mountainous, semi-arid ponderosa pine-dominated forest site that is normally dominated by clean continental air, but is periodically influenced by anthropogenic sources from Colorado Front Range cities. This article summarizes the past and ongoing research activities at the site, and highlights some of the significant findings that have resulted from these measurements. These activities include: – soil property measurements, – hydrological studies, – measurements of high-frequency turbulence parameters, – eddy covariance flux measurements of water, energy, aerosols and carbon dioxide through the canopy, – biogenic and anthropogenic volatile organic compound emissions and their influence on regional atmospheric chemistry, – aerosol number and mass distributions, – chemical speciation of aerosol particles, – characterization of ice and cloud condensation nuclei, – trace gas measurements, and – model simulations using coupled chemistry and meteorology. In addition to various long-term continuous measurement, three focused measurement campaigns with state-of-the-art instrumentation have taken place since the site was established, and two of these are the subjects of this special issue: BEACHON-ROCS (Rocky Mountain Organic Carbon Study, 2010) and BEACHON-RoMBAS (Rocky Mountain Biogenic Aerosol Study, 2011).
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Bates, T. S., T. L. Anderson, T. Baynard, T. Bond, O. Boucher, G. Carmichael, A. Clarke, et al. "Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oceans: estimates based on in-situ chemical and optical measurements and chemical transport modeling." Atmospheric Chemistry and Physics 6, no. 6 (May 22, 2006): 1657–732. http://dx.doi.org/10.5194/acp-6-1657-2006.
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Abstract. The largest uncertainty in the radiative forcing of climate change over the industrial era is that due to aerosols, a substantial fraction of which is the uncertainty associated with scattering and absorption of shortwave (solar) radiation by anthropogenic aerosols in cloud-free conditions (IPCC, 2001). Quantifying and reducing the uncertainty in aerosol influences on climate is critical to understanding climate change over the industrial period and to improving predictions of future climate change for assumed emission scenarios. Measurements of aerosol properties during major field campaigns in several regions of the globe during the past decade are contributing to an enhanced understanding of atmospheric aerosols and their effects on light scattering and climate. The present study, which focuses on three regions downwind of major urban/population centers (North Indian Ocean (NIO) during INDOEX, the Northwest Pacific Ocean (NWP) during ACE-Asia, and the Northwest Atlantic Ocean (NWA) during ICARTT), incorporates understanding gained from field observations of aerosol distributions and properties into calculations of perturbations in radiative fluxes due to these aerosols. This study evaluates the current state of observations and of two chemical transport models (STEM and MOZART). Measurements of burdens, extinction optical depth (AOD), and direct radiative effect of aerosols (DRE – change in radiative flux due to total aerosols) are used as measurement-model check points to assess uncertainties. In-situ measured and remotely sensed aerosol properties for each region (mixing state, mass scattering efficiency, single scattering albedo, and angular scattering properties and their dependences on relative humidity) are used as input parameters to two radiative transfer models (GFDL and University of Michigan) to constrain estimates of aerosol radiative effects, with uncertainties in each step propagated through the analysis. Constraining the radiative transfer calculations by observational inputs increases the clear-sky, 24-h averaged AOD (34±8%), top of atmosphere (TOA) DRE (32±12%), and TOA direct climate forcing of aerosols (DCF – change in radiative flux due to anthropogenic aerosols) (37±7%) relative to values obtained with "a priori" parameterizations of aerosol loadings and properties (GFDL RTM). The resulting constrained clear-sky TOA DCF is −3.3±0.47, −14±2.6, −6.4±2.1 Wm−2 for the NIO, NWP, and NWA, respectively. With the use of constrained quantities (extensive and intensive parameters) the calculated uncertainty in DCF was 25% less than the "structural uncertainties" used in the IPCC-2001 global estimates of direct aerosol climate forcing. Such comparisons with observations and resultant reductions in uncertainties are essential for improving and developing confidence in climate model calculations incorporating aerosol forcing.
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Verma, T. S., K. S. Madhava Rao, and Shibu K. John. "AN ASSESSMENT OF SEVERITY OF ENVIRONMENTAL AEROSOL PARTICLES DURING PRECIPITATION." International Journal of Environment 4, no. 3 (August 24, 2015): 81–95. http://dx.doi.org/10.3126/ije.v4i3.13232.
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Africa is one of the sources of biomass burning emissions. It is estimated that about 6 million tons of fuel per day is consumed in the southern hemisphere. Biomass burning has an important contribution on aerosol particle concentrations in the atmosphere. Efforts have been made to conduct research in Gaborone to monitor the concentration of atmospheric aerosols in atmosphere. These studies were mainly confined to measurement of concentration of aerosols and establishing a relation with determinants such as carbon dioxide concentration, biomass burning, and precipitation among others. However, very little seems to have been done in relating the empirical data to a mathematical model or to study quantitatively the impact of precipitation on the concentration of aerosols larger than 0.3?m in the atmosphere. In this paper we provide an objective criterion for classifying measurements on concentration of atmospheric aerosol particles and build a mathematical model that helps us to understand variations in weekly aerosol concentrations in terms of their severity. We also construct an index of severity which when applied to different seasons under the study period indicates that precipitation significantly scavenges atmospheric aerosols.International Journal of Environment Volume-4, Issue-3, June-August 2015Page: 81-95
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Drewnick, F., J. M. Diesch, P. Faber, and S. Borrmann. "Aerosol mass spectrometry: particle–vaporizer interactions and their consequences for the measurements." Atmospheric Measurement Techniques 8, no. 9 (September 18, 2015): 3811–30. http://dx.doi.org/10.5194/amt-8-3811-2015.
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Abstract. The Aerodyne aerosol mass spectrometer (AMS) is a frequently used instrument for on-line measurement of the ambient sub-micron aerosol composition. With the help of calibrations and a number of assumptions on the flash vaporization and electron impact ionization processes, this instrument provides robust quantitative information on various non-refractory ambient aerosol components. However, when measuring close to certain anthropogenic or marine sources of semi-refractory aerosols, several of these assumptions may not be met and measurement results might easily be incorrectly interpreted if not carefully analyzed for unique ions, isotope patterns, and potential slow vaporization associated with semi-refractory species. Here we discuss various aspects of the interaction of aerosol particles with the AMS tungsten vaporizer and the consequences for the measurement results: semi-refractory components – i.e., components that vaporize but do not flash-vaporize at the vaporizer and ionizer temperatures, like metal halides (e.g., chlorides, bromides or iodides of Al, Ba, Cd, Cu, Fe, Hg, K, Na, Pb, Sr, Zn) – can be measured semi-quantitatively despite their relatively slow vaporization from the vaporizer. Even though non-refractory components (e.g., NH4NO3 or (NH4)2SO4) vaporize quickly, under certain conditions their differences in vaporization kinetics can result in undesired biases in ion collection efficiency in thresholded measurements. Chemical reactions with oxygen from the aerosol flow can have an influence on the mass spectra for certain components (e.g., organic species). Finally, chemical reactions of the aerosol with the vaporizer surface can result in additional signals in the mass spectra (e.g., WO2Cl2-related signals from particulate Cl) and in conditioning or contamination of the vaporizer, with potential memory effects influencing the mass spectra of subsequent measurements. Laboratory experiments that investigate these particle–vaporizer interactions are presented and are discussed together with field results, showing that measurements of typical continental or urban aerosols are not significantly affected, while measurements of semi-refractory aerosol in the laboratory, close to anthropogenic sources or in marine environments, can be biased by these effects.
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Iziomon, M. G., and U. Lohmann. "Characteristics and direct radiative effect of mid-latitude continental aerosols: the ARM case." Atmospheric Chemistry and Physics 3, no. 6 (November 3, 2003): 1903–17. http://dx.doi.org/10.5194/acp-3-1903-2003.
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Abstract. A multi-year field measurement analysis of the characteristics and direct radiative effect of aerosols at the Southern Great Plains (SGP) central facility of the Atmospheric Radiation Measurement (ARM) Program is presented. Inter-annual mean and standard deviation of submicrometer scattering fraction (at 550 nm) and Ångström exponent å (450 nm, 700 nm) at the mid-latitude continental site are indicative of the scattering dominance of fine mode aerosol particles, being 0.84±0.03 and 2.25±0.09, respectively. We attribute the diurnal variation of submicron aerosol concentration to coagulation, photochemistry and the evolution of the boundary layer. Precipitation does not seem to play a role in the observed afternoon maximum in aerosol concentration. Submicron aerosol mass at the site peaks in the summer (12.1±6.7mg m-3), with the summer value being twice that in the winter. Of the chemically analyzed ionic components (which exclude carbonaceous aerosols), SO4= and NH4+ constitute the dominant species at the SGP seasonally, contributing 23-30% and 9-12% of the submicron aerosol mass, respectively. Although a minor species, there is a notable rise in NO3- mass fraction in winter. We contrast the optical properties of dust and smoke haze. The single scattering albedo w0 shows the most remarkable distinction between the two aerosol constituents. We also present aircraft measurements of vertical profiles of aerosol optical properties at the site. Annually, the lowest 1.2 km contributes 70% to the column total light scattering coefficient. Column-averaged and surface annual mean values of hemispheric backscatter fraction (at 550 nm), w0 (at 550 nm) and å (450 nm, 700 nm) agree to within 5% in 2001. Aerosols produce a net cooling (most pronounced in the spring) at the ARM site
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Petäjä, Tuukka, Ewan J. O’Connor, Dmitri Moisseev, Victoria A. Sinclair, Antti J. Manninen, Riikka Väänänen, Annakaisa von Lerber, et al. "BAECC: A Field Campaign to Elucidate the Impact of Biogenic Aerosols on Clouds and Climate." Bulletin of the American Meteorological Society 97, no. 10 (October 1, 2016): 1909–28. http://dx.doi.org/10.1175/bams-d-14-00199.1.
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Abstract During Biogenic Aerosols—Effects on Clouds and Climate (BAECC), the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) Program deployed the Second ARM Mobile Facility (AMF2) to Hyytiälä, Finland, for an 8-month intensive measurement campaign from February to September 2014. The primary research goal is to understand the role of biogenic aerosols in cloud formation. Hyytiälä is host to the Station for Measuring Ecosystem–Atmosphere Relations II (SMEAR II), one of the world’s most comprehensive surface in situ observation sites in a boreal forest environment. The station has been measuring atmospheric aerosols, biogenic emissions, and an extensive suite of parameters relevant to atmosphere–biosphere interactions continuously since 1996. Combining vertical profiles from AMF2 with surface-based in situ SMEAR II observations allows the processes at the surface to be directly related to processes occurring throughout the entire tropospheric column. Together with the inclusion of extensive surface precipitation measurements and intensive observation periods involving aircraft flights and novel radiosonde launches, the complementary observations provide a unique opportunity for investigating aerosol–cloud interactions and cloud-to-precipitation processes in a boreal environment. The BAECC dataset provides opportunities for evaluating and improving models of aerosol sources and transport, cloud microphysical processes, and boundary layer structures. In addition, numerical models are being used to bridge the gap between surface-based and tropospheric observations.
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Zhang, Yue, Shachi Katira, Andrew Lee, Andrew T. Lambe, Timothy B. Onasch, Wen Xu, William A. Brooks, et al. "Kinetically controlled glass transition measurement of organic aerosol thin films using broadband dielectric spectroscopy." Atmospheric Measurement Techniques 11, no. 6 (June 19, 2018): 3479–90. http://dx.doi.org/10.5194/amt-11-3479-2018.
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Abstract. Glass transitions from liquid to semi-solid and solid phase states have important implications for reactivity, growth, and cloud-forming (cloud condensation nuclei and ice nucleation) capabilities of secondary organic aerosols (SOAs). The small size and relatively low mass concentration of SOAs in the atmosphere make it difficult to measure atmospheric SOA glass transitions using conventional methods. To circumvent these difficulties, we have adapted a new technique for measuring glass-forming properties of atmospherically relevant organic aerosols. Aerosol particles to be studied are deposited in the form of a thin film onto an interdigitated electrode (IDE) using electrostatic precipitation. Dielectric spectroscopy provides dipole relaxation rates for organic aerosols as a function of temperature (373 to 233 K) that are used to calculate the glass transition temperatures for several cooling or heating rates. IDE-enabled broadband dielectric spectroscopy (BDS) was successfully used to measure the kinetically controlled glass transition temperatures of aerosols consisting of glycerol and four other compounds with selected cooling and heating rates. The glass transition results agree well with available literature data for these five compounds. The results indicate that the IDE-BDS method can provide accurate glass transition data for organic aerosols under atmospheric conditions. The BDS data obtained with the IDE-BDS technique can be used to characterize glass transitions for both simulated and ambient organic aerosols and to model their climate effects.
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Bates, T. S., T. L. Anderson, T. Baynard, T. Bond, O. Boucher, G. Carmichael, A. Clarke, et al. "Aerosol direct radiative effects over the northwest Atlantic, northwest Pacific, and North Indian Oceans: estimates based on in-situ chemical and optical measurements and chemical transport modeling." Atmospheric Chemistry and Physics Discussions 6, no. 1 (January 3, 2006): 175–362. http://dx.doi.org/10.5194/acpd-6-175-2006.
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Abstract. The largest uncertainty in the radiative forcing of climate change over the industrial era is that due to aerosols, a substantial fraction of which is the uncertainty associated with scattering and absorption of shortwave (solar) radiation by anthropogenic aerosols in cloud-free conditions (IPCC, 2001). Quantifying and reducing the uncertainty in aerosol influences on climate is critical to understanding climate change over the industrial period and to improving predictions of future climate change for assumed emission scenarios. Measurements of aerosol properties during major field campaigns in several regions of the globe during the past decade are contributing to an enhanced understanding of atmospheric aerosols and their effects on light scattering and climate. The present study, which focuses on three regions downwind of major urban/population centers (North Indian Ocean (NIO) during INDOEX, the Northwest Pacific Ocean (NWP) during ACE-Asia, and the Northwest Atlantic Ocean (NWA) during ICARTT), incorporates understanding gained from field observations of aerosol distributions and properties into calculations of perturbations in radiative fluxes due to these aerosols. This study evaluates the current state of observations and of two chemical transport models (STEM and MOZART). Measurements of burdens, extinction optical depth (AOD), and direct radiative effect of aerosols (DRE – change in radiative flux due to total aerosols) are used as measurement-model check points to assess uncertainties. In-situ measured and remotely sensed aerosol properties for each region (mixing state, mass scattering efficiency, single scattering albedo, and angular scattering properties and their dependences on relative humidity) are used as input parameters to two radiative transfer models (GFDL and University of Michigan) to constrain estimates of aerosol radiative effects, with uncertainties in each step propagated through the analysis. Constraining the radiative transfer calculations by observational inputs increases the clear-sky, 24-h averaged AOD (34±8%), top of atmosphere (TOA) DRE (32±12%), and TOA direct climate forcing of aerosols (DCF – change in radiative flux due to anthropogenic aerosols) (37±7%) relative to values obtained with "a priori" parameterizations of aerosol loadings and properties (GFDL RTM). The resulting constrained TOA DCF is −3.3±0.47, −14±2.6, −6.4±2.1 Wm−2 for the NIO, NWP, and NWA, respectively. Constraining the radiative transfer calculations by observational inputs reduces the uncertainty range in the DCF in these regions relative to global IPCC (2001) estimates by a factor of approximately 2. Such comparisons with observations and resultant reductions in uncertainties are essential for improving and developing confidence in climate model calculations incorporating aerosol forcing.
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Timonen, H., S. Saarikoski, O. Tolonen-Kivimäki, M. Aurela, K. Saarnio, T. Petäjä, P. P. Aalto, M. Kulmala, T. Pakkanen, and R. Hillamo. "Size distributions, sources and source areas of water-soluble organic carbon in urban background air." Atmospheric Chemistry and Physics Discussions 8, no. 2 (April 21, 2008): 7847–81. http://dx.doi.org/10.5194/acpd-8-7847-2008.
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Abstract. This paper represents the results of one year long measurement period of the size distributions of water-soluble organic carbon (WSOC), inorganic ions and gravimetric mass of particulate matter. Measurements were done at an urban background station (SMEAR III) by using a micro-orifice uniform deposit impactor (MOUDI). The site is located in northern European boreal region in Helsinki, Finland. The WSOC size distribution measurements were completed with the chemical analysis of inorganic ions, organic carbon (OC) and monosaccharide anhydrides from the filter samples. During the measurements gravimetric mass in the MOUDI collections varied between 3.4 and 55.0 μg m−3 and the WSOC concentration was between 0.3 and 7.4 μg m−3. On average, water-soluble particulate organic matter (WSPOM, WSOC multiplied by 1.6) comprised 25±7.7% and 7.5±3.4% of aerosol PM1 mass and the PM1−10 mass, respectively. Inorganic ions contributed 33±12% and 28±19% of the analyzed PM1 and PM1−10 aerosol mass. Five different aerosol categories corresponding to different sources or source areas were identified (long-range transport aerosols, biomass burning aerosols from wild land fires and from small-scale wood combustion, aerosols originating from marine areas and from the clean arctic areas). Clear differences in WSOC concentrations and size distributions originating from different sources or source areas were observed, although there are also many other factors which might affect the results. E.g. the local conditions and sources of volatile organic compounds (VOCs) and aerosols as well as various transformation processes are likely to have an impact on the measured aerosol composition. Using the source categories, it was identified that especially the oxidation products of biogenic VOCs in summer had a clear effect on WSOC concentrations.
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Schneider, T. "Indoor aerosols: measurement and analysis." Journal of Aerosol Science 22 (1991): S817—S822. http://dx.doi.org/10.1016/s0021-8502(05)80225-3.
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Cheng, Y. S., B. T. Chen, and H. C. Yeh. "Size measurement of liquid aerosols." Journal of Aerosol Science 17, no. 5 (January 1986): 803–9. http://dx.doi.org/10.1016/0021-8502(86)90034-0.
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Görner, P., D. Bemer, and J. F. Fabriés. "Photometer measurement of polydisperse aerosols." Journal of Aerosol Science 26, no. 8 (December 1995): 1281–302. http://dx.doi.org/10.1016/0021-8502(95)00049-6.
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Panahifar, Hossein, Farizeh Bayat, and Tareq Hussein. "Simultaneous Use of Ground-Based and Satellite Observation to Evaluate Atmospheric Air Pollution over Amman, Jordan." Atmosphere 14, no. 2 (January 30, 2023): 274. http://dx.doi.org/10.3390/atmos14020274.
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In this study, a combination of ground-based particulate matter measurements in synergy with space-borne CALIOP lidar recordings, meteorological observations, and reanalysis models have been used to study atmospheric air pollution over Amman, Jordan. The measurement was conducted over a 24-month period spanning from January 2018 to the end of December 2019. The CALIOP aerosol profiles and aerosol layer products version 4.21, level 2, with 5 km horizontal resolution were used to evaluate the vertical structure of the atmospheric constituent over the Amman region. The particle depolarization ratio (PDR) was extracted from CALIOP recordings and has been utilized to classify the type of atmospheric aerosols. This method reveals that the atmosphere above Amman mostly contains three different aerosol types including coarse-mode dust, fine-mode dust (polluted dust), and non-dust aerosols (pollution). Aerosols with 0 < δp≤ 0.075 are categorized as pollution, aerosols with 0.075 < δp≤ 0.20 as polluted dust, and aerosols with 0.20 < δp≤ 0.40 are classified as dust. Both the one- and two-step POlarization-LIdar PHOtometer Networking (POLIPHON) approaches have been applied to the CALIOP aerosol profile product to retrieve the vertical profile of the optical and micro-physical properties of each aerosol type. Lofted-layer top heights and layer thickness in the atmosphere above Amman during the study period were also extracted from the CALIOP aerosol layer products. The highest frequency of occurrence was observed for layers with a top height of 0.5 to 2.5 km with a second smaller peak at 3.5 km. The maximum frequency of the lofted layers (40% of cases) were observed with layer thickness below 0.5 km. For layers with a top height lower than 500 m above ground level, the atmosphere was mostly impacted by polluted dust and pollution aerosols. On the other hand, for layers with a top height above 2500 m agl, the atmosphere was contaminated by depolarizing dust particles.
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Cao, Li-Ming, Xiao-Feng Huang, Yuan-Yuan Li, Min Hu, and Ling-Yan He. "Volatility measurement of atmospheric submicron aerosols in an urban atmosphere in southern China." Atmospheric Chemistry and Physics 18, no. 3 (February 6, 2018): 1729–43. http://dx.doi.org/10.5194/acp-18-1729-2018.
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Abstract. Aerosol pollution has been a very serious environmental problem in China for many years. The volatility of aerosols can affect the distribution of compounds in the gas and aerosol phases, the atmospheric fates of the corresponding components, and the measurement of the concentration of aerosols. Compared to the characterization of chemical composition, few studies have focused on the volatility of aerosols in China. In this study, a thermodenuder aerosol mass spectrometer (TD-AMS) system was deployed to study the volatility of non-refractory submicron particulate matter (PM1) species during winter in Shenzhen. To our knowledge, this paper is the first report of the volatilities of aerosol chemical components based on a TD-AMS system in China. The average PM1 mass concentration during the experiment was 42.7±20.1 µg m−3, with organic aerosol (OA) being the most abundant component (43.2 % of the total mass). The volatility of chemical species measured by the AMS varied, with nitrate showing the highest volatility, with a mass fraction remaining (MFR) of 0.57 at 50 ∘C. Organics showed semi-volatile characteristics (the MFR was 0.88 at 50 ∘C), and the volatility had a relatively linear correlation with the TD temperature (from the ambient temperature to 200 ∘C), with an evaporation rate of 0.45 %∘C-1. Five subtypes of OA were resolved from total OA using positive matrix factorization (PMF) for data obtained under both ambient temperature and high temperatures through the TD, including a hydrocarbon-like OA (HOA, accounting for 13.5 %), a cooking OA (COA, 20.6 %), a biomass-burning OA (BBOA, 8.9 %), and two oxygenated OAs (OOAs): a less-oxidized OOA (LO-OOA, 39.1 %) and a more-oxidized OOA (MO-OOA, 17.9 %). Different OA factors presented different volatilities, and the volatility sequence of the OA factors at 50 ∘C was HOA (MFR of 0.56) > LO-OOA (0.70) > COA (0.85) ≈ BBOA (0.87) > MO-OOA (0.99), which was not completely consistent with the sequence of their O ∕ C ratios. The high volatility of HOA implied that it had a high potential to be oxidized to secondary species in the gas phase. The aerosol volatility measurement results in this study provide useful parameters for the modeling work of aerosol evolution in China and are also helpful in understanding the formation mechanisms of secondary aerosols.