Special Issue "Remote Sensing of Aerosols"

A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Aerosols".

Deadline for manuscript submissions: closed (20 April 2019).

Special Issue Editor

Guest Editor
Dr. Francisco Molero

Department of Environment, Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas (CIEMAT), Avda Complutense, 40. Madrid 28040, Spain
Website | E-Mail
Interests: characterization of atmospheric aerosols; remote sensing; aerosol radiative forcing

Special Issue Information

Dear Colleagues,

Recent developments in remote sensing, such as novel satellite technologies (LiDAR, polarized or multi-angle techniques) or coordination of ground-based instruments as networks, have allowed a better characterization of aerosols at a global scale. Aerosols play an important role in the radiative balance of the Earth climate system. Nowadays, a large uncertainty is assigned to the indirect effect of aerosols, related with their interaction with clouds. This is mainly due to the highly variable aerosol properties in space and time. Present climate models account for this variability by parametrizing the aerosol emissions, formation in the atmosphere and transport.

A significant progress in the characterization of the aerosol distribution, life-cycles and profiles has been provided by recent developments in remote sensing techniques. This allows a better estimation of heating/cooling radiative rates, which plays an important role in atmospheric chemistry, and aerosol properties under cloudy conditions, crucial for a better understanding of the indirect effect.

This Special Issue aims at improving the present understanding of the effect of spatial and temporal distribution of aerosols on climate. Contributions about development of novel remote sensing, application of network measurements and modelling of aerosol distribution are welcome.

 

Dr. Francisco Molero
Guest Editor

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Keywords

  • aerosols
  • radiative forcing
  • remote sensing
  • satellite
  • ground-based instrumentation
  • aerosol transport
  • aerosol vertical profiles

Published Papers (8 papers)

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Research

Open AccessArticle
Comparison of Columnar, Surface, and UAS Profiles of Absorbing Aerosol Optical Depth and Single-Scattering Albedo in South-East Poland
Atmosphere 2019, 10(8), 446; https://doi.org/10.3390/atmos10080446
Received: 3 July 2019 / Revised: 23 July 2019 / Accepted: 23 July 2019 / Published: 2 August 2019
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Abstract
The impact of absorbing aerosols on climate is complex, with their potential positive or negative forcing, depending on many factors, including their height distribution and reflective properties of the underlying background. Measurement data is very limited, due to insufficient remote sensing methods dedicated [...] Read more.
The impact of absorbing aerosols on climate is complex, with their potential positive or negative forcing, depending on many factors, including their height distribution and reflective properties of the underlying background. Measurement data is very limited, due to insufficient remote sensing methods dedicated to the retrieval of their vertical distribution. Columnar values of absorbing aerosol optical depth (AAOD) and single scattering albedo (SSA) are retrieved by the Aerosol Robotic Network (AERONET). However, the number of available results is low due to sky condition and aerosol optical depth (AOD) limitation. Presented research describes results of field campaigns in Strzyżów (South-East Poland, Eastern Europe) dedicated to the comparison of the absorption coefficient and SSA measurements performed with on-ground in-situ devices (aethalomter, nephelometer), small unmanned aerial system (UAS) carrying micro-aethalometer, as well as with lidar/ceilometer. An important aspect is the comparison of measurement results with those delivered by AERONET. Correlation of absorption to scattering coefficients measured on ground (0.79) and correlation of extinction on ground to AOD measured by AERONET (0.77) was visibly higher than correlation between AOD and AAOD retrieved by AERONET (0.56). Columnar SSA was weakly correlated with ground SSA (higher values of columnar SSA), which were mainly explained by hygroscopic effects, increasing scattering coefficient in ambient (wet conditions), and partly high uncertainty of SSA retrieval. AAOD derived with the use of profiles from UAS up to PBL height, was estimated to contribute in average to 37% of the total AAOD. A method of AAOD estimation, in the whole troposphere, with use of measured vertical profiles of absorption coefficient and extinction coefficient profiles from lidars was proposed. AAOD measured with this method has poor correlation with AERONET data, however for some measurements, within PBL, AAOD was higher than reported by AERONET, suggesting potential underestimation in photometric measurement under particular conditions. Correlation of absorption coefficient in profile to on ground measurements decrease with altitude. Measurements of SSA from drones agree well with ground measurements and are lower than results from AERONET, which suggests a larger contribution of absorbing aerosols. As an alternative for AAOD estimation in case of lack of AERONET AAOD data simple models are proposed, which base on AOD scaling with SSA measured with different methods. Proposed solution increase potential of absorption coefficient measurements in vertical profiles and columns of the atmosphere. Presented solutions make measurements of absorption coefficients in vertical profiles more affordable and allow rough estimation of columnar values for the whole atmosphere. Full article
(This article belongs to the Special Issue Remote Sensing of Aerosols)
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Open AccessArticle
Analysis of a Haze Event over Nanjing, China Based on Multi-Source Data
Atmosphere 2019, 10(6), 338; https://doi.org/10.3390/atmos10060338
Received: 22 May 2019 / Revised: 12 June 2019 / Accepted: 17 June 2019 / Published: 20 June 2019
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Abstract
We analyzed a June 2018 Nanjing, China haze event using ground-based and spaceborne sensors, combined with sounding and HYSPLIT backward trajectory data, with the ground-based and spaceborne sensor data exhibiting good consistency. Water vapor content showed significant positive correlation with AOD (aerosol optical [...] Read more.
We analyzed a June 2018 Nanjing, China haze event using ground-based and spaceborne sensors, combined with sounding and HYSPLIT backward trajectory data, with the ground-based and spaceborne sensor data exhibiting good consistency. Water vapor content showed significant positive correlation with AOD (aerosol optical depth), and AOD measured in urban and industrial areas was much higher compared to other similar zones. The afternoon convection caused the aerosol uplift during the haze event. Higher aerosol concentration was detected below 2 km. Due to the summer afternoon convective movement, pollutants at high altitude were dominated by small particles, while the overall pollutant mix was dominated by mixed aerosols. During a stable period over June 11–18, a single, near-surface inversion layer, and occasional two inversion layers, stopped pollutant dispersal, with only very stable ocean air mass transport in the southeast direction available. The Air Quality Index drop which took place during June 28–30 was caused by two inversion layers, combined with the immigration of pollutants from inland air masses. Full article
(This article belongs to the Special Issue Remote Sensing of Aerosols)
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Open AccessArticle
New Regression Method to Merge Different MODIS Aerosol Products Based on NDVI Datasets
Atmosphere 2019, 10(6), 303; https://doi.org/10.3390/atmos10060303
Received: 15 April 2019 / Revised: 19 May 2019 / Accepted: 20 May 2019 / Published: 3 June 2019
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Abstract
The moderate resolution and imaging spectroradiometer (MODIS) level 2 operational aerosol products that are based on the dark target (DT) method over vegetated regions and the enhanced deep blue (DB) algorithms over bright pixels provide daily global aerosol optical depth (AOD). However, increasing [...] Read more.
The moderate resolution and imaging spectroradiometer (MODIS) level 2 operational aerosol products that are based on the dark target (DT) method over vegetated regions and the enhanced deep blue (DB) algorithms over bright pixels provide daily global aerosol optical depth (AOD). However, increasing the data coverage by merging the DT and DB merged AOD product has recently become the focus of research. Therefore, this study aims to improve the merged AOD performance by introducing a new regression method (DTBRG), depending on the normalized difference vegetation index values when DT and DB AOD are valid. The DTBRG AOD is validated on a global scale while using aerosol robot network AOD measurements. Merged AOD550s from the MODIS official method and Bilal’s customized methods are evaluated for the same period for comparison. The inter-comparison of merged AOD550s from different methods with an equal number of coincident observations demonstrates that the DTBRG method performs better than the MODIS official algorithm with increased expected error (83% versus 76%), R (0.92 versus 0.90), and decreased bias (−0.001 versus 0.012). Therefore, it can be operationally used for global merged aerosol retrievals. Full article
(This article belongs to the Special Issue Remote Sensing of Aerosols)
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Open AccessArticle
Aerosol Optical Thickness over Large Urban Environments of the Arabian Peninsula—Speciation, Variability, and Distributions
Atmosphere 2019, 10(5), 228; https://doi.org/10.3390/atmos10050228
Received: 3 April 2019 / Revised: 23 April 2019 / Accepted: 26 April 2019 / Published: 29 April 2019
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Abstract
The Arabian Peninsula is one of the world’s largest sources of mineral dust that includes several major population hotspots. However, until now, few studies have performed a comprehensive quantification of the long-term variability of aerosol species in this region. In this study, the [...] Read more.
The Arabian Peninsula is one of the world’s largest sources of mineral dust that includes several major population hotspots. However, until now, few studies have performed a comprehensive quantification of the long-term variability of aerosol species in this region. In this study, the speciation, variability, and distribution of aerosol optical depth over the Arabian Peninsula during 2005–2015 is analyzed by using the modern-era retrospective analysis for research and applications, Version 2 (MERRA-2) model together with satellite retrieved data and AERONET observations and focusing on nine large cities in the region (Dammam, Doha, Dubai, Jeddah, Kuwait, Manama, Muscat, Riyadh, and Sanaa). Over the past decade, the mean annual aerosol optical thickness (AOT) values were in the range of 0.3–0.5, which is attributed to both mineral dust (60–70%) and anthropogenic activities (20–30%). An increase in AOT values between 2005 and 2009 is attributed to increased dust generation from the Sahel region in Northern Africa, and the Fertile Crescent (Syria, Iraq, Jordan) due to an extended dry period. Reductions in local urban emissions are still considered to be efficient measures to improve air quality in these population centers despite the significant contribution of desert dust in the total particulate matter levels in the region. Full article
(This article belongs to the Special Issue Remote Sensing of Aerosols)
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Open AccessArticle
Optimal Estimation Retrieval of Aerosol Fine-Mode Fraction from Ground-Based Sky Light Measurements
Atmosphere 2019, 10(4), 196; https://doi.org/10.3390/atmos10040196
Received: 18 March 2019 / Revised: 4 April 2019 / Accepted: 9 April 2019 / Published: 11 April 2019
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Abstract
In this paper, the feasibility of retrieving the aerosol fine-mode fraction (FMF) from ground-based sky light measurements is investigated. An inversion algorithm, based on the optimal estimation (OE) theory, is presented to retrieve FMF from single-viewing multi-spectral radiance measurements and to evaluate the [...] Read more.
In this paper, the feasibility of retrieving the aerosol fine-mode fraction (FMF) from ground-based sky light measurements is investigated. An inversion algorithm, based on the optimal estimation (OE) theory, is presented to retrieve FMF from single-viewing multi-spectral radiance measurements and to evaluate the impact of utilization of near-infrared (NIR) measurements at a wavelength of 1610 nm in aerosol remote sensing. Self-consistency tests based on synthetic data produced a mean relative retrieval error of 4.5%, which represented the good performance of the OE inversion algorithm. The proposed algorithm was also performed on real data taken from field experiments in Beijing during a haze pollution event. The correlation coefficients (R) for the retrieved aerosol volume fine-mode fraction (FMFv) and optical fine-mode fraction (FMFo) against AErosol RObotic NETwork (AERONET) products were 0.94 and 0.95 respectively, and the mean residual error was 4.95%. Consequently, the inversion of FMFv and FMFo could be well constrained by single-viewing multi-spectral radiance measurement. In addition, by introducing measurements of 1610 nm wavelength into the retrieval, the validation results showed a significant improvement in the R value for FMFo (from 0.89–0.94). These results confirm the high value of NIR measurements for the retrieval of coarse mode aerosols. Full article
(This article belongs to the Special Issue Remote Sensing of Aerosols)
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Open AccessArticle
A Short Note on the Potential of Utilization of Spectral AERONET-Derived Depolarization Ratios for Aerosol Classification
Atmosphere 2019, 10(3), 143; https://doi.org/10.3390/atmos10030143
Received: 8 February 2019 / Revised: 9 March 2019 / Accepted: 12 March 2019 / Published: 16 March 2019
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Abstract
We herein present the spectral linear particle depolarization ratios (δp) from an Aerosol Robotics NETwork (AERONET) sun/sky radiometer with respect to the aerosol type. AERONET observation sites, which are representative of each aerosol type, were selected for our study. The observation [...] Read more.
We herein present the spectral linear particle depolarization ratios (δp) from an Aerosol Robotics NETwork (AERONET) sun/sky radiometer with respect to the aerosol type. AERONET observation sites, which are representative of each aerosol type, were selected for our study. The observation data were filtered using the Ångström exponent (Å), fine-mode fraction (FMF) and single scattering albedo (ω) to ensure that the obtained values of δp were representative of each aerosol condition. We report the spectral δp values provided in the recently released AERONET version 3 inversion product for observation of the following aerosol types: dust, polluted dust, smoke, non-absorbing, moderately-absorbing and high-absorbing pollution. The AERONET-derived δp values were generally within the range of the δp values measured from lidar observations for each aerosol type. In addition, it was found that the spectral variation of δp differed according to the aerosol type. From the obtained results, we concluded that our findings provide potential insight into the identification and classification of aerosol types using remote sensing techniques. Full article
(This article belongs to the Special Issue Remote Sensing of Aerosols)
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Open AccessArticle
Investigation of Aerosol Properties and Structures in Two Representative Meteorological Situations over the Vipava Valley Using Polarization Raman LiDAR
Atmosphere 2019, 10(3), 128; https://doi.org/10.3390/atmos10030128
Received: 30 January 2019 / Revised: 1 March 2019 / Accepted: 5 March 2019 / Published: 8 March 2019
Cited by 1 | PDF Full-text (3189 KB) | HTML Full-text | XML Full-text
Abstract
Vipava valley in Slovenia is a representative hot-spot for complex mixtures of different aerosol types of both anthropogenic and natural origin. Aerosol loading distributions and optical properties were investigated using a two-wavelength polarization Raman LiDAR, which provided extinction coefficient, backscatter coefficient, depolarization ratio, [...] Read more.
Vipava valley in Slovenia is a representative hot-spot for complex mixtures of different aerosol types of both anthropogenic and natural origin. Aerosol loading distributions and optical properties were investigated using a two-wavelength polarization Raman LiDAR, which provided extinction coefficient, backscatter coefficient, depolarization ratio, backscatter Ångström exponent and LiDAR ratio profiles. Two different representative meteorological situations were investigated to explore the possibility of identifying aerosol types present in the valley. In the first case, we investigated the effect of strong downslope (Bora) wind on aerosol structures and characteristics. In addition to observing Kelvin–Helmholtz instability above the valley, at the height of the adjacent mountain ridge, we found new evidence for Bora-induced processes which inject soil dust aerosols into the free troposphere up to twice the height of the planetary boundary layer (PBL). In the second case, we investigated aerosol properties and distributions in stable weather conditions. From the observed stratified vertical aerosol structure and specific optical properties of different layers we identified predominant aerosol types in these layers. Full article
(This article belongs to the Special Issue Remote Sensing of Aerosols)
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Open AccessArticle
A Turbulence-Oriented Approach to Retrieve Various Atmospheric Parameters Using Advanced Lidar Data Processing Techniques
Atmosphere 2019, 10(1), 38; https://doi.org/10.3390/atmos10010038
Received: 17 November 2018 / Revised: 12 January 2019 / Accepted: 14 January 2019 / Published: 18 January 2019
Cited by 1 | PDF Full-text (9914 KB) | HTML Full-text | XML Full-text
Abstract
The article is aimed at presenting a semi-empirical model coded and computed in the programming language Python, which utilizes data gathered with a standard biaxial elastic lidar platform in order to calculate the altitude profiles of the structure coefficients of the atmospheric refraction [...] Read more.
The article is aimed at presenting a semi-empirical model coded and computed in the programming language Python, which utilizes data gathered with a standard biaxial elastic lidar platform in order to calculate the altitude profiles of the structure coefficients of the atmospheric refraction index C N 2 ( z ) and other associated turbulence parameters. Additionally, the model can be used to calculate the PBL (Planetary Boundary Layer) height, and other parameters typically employed in the field of astronomy. Solving the Fernard–Klett inversion by correlating sun-photometer data obtained through our AERONET site with lidar data, it can yield the atmospheric extinction and backscatter profiles α ( z ) and β ( z ) , and thus obtain the atmospheric optical depth. Finally, several theoretical notions of interest that utilize the solved parameters are presented, such as approximated relations between C N 2 ( z ) and the atmospheric temperature profile T ( z ) , and between the scintillation of backscattered lidar signal and the average wind speed profile U ( z ) . These obtained profiles and parameters also have several environmental applications that are connected directly and indirectly to human health and well-being, ranging from understanding the transport of aerosols in the atmosphere and minimizing the errors in measuring it, to predicting extreme, and potentially-damaging, meteorological events. Full article
(This article belongs to the Special Issue Remote Sensing of Aerosols)
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