Special Issue "Atmospheric Aerosols and Their Radiative Effects"

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

Deadline for manuscript submissions: closed (31 December 2016).

Special Issue Editors

Dr. Giovanni Pitari
grade E-Mail Website
Guest Editor
Department of Physical and Chemical Sciences, Università degli Studi dell’Aquila, 67010 Coppito, L’Aquila, Italy
Tel. +39-0862-433074
Interests: global and regional modeling of atmospheric aerosols and their radiative effects; climate-chemistry interactions related to stratospheric ozone; intercontinental transport of trace gases and aerosols; aerosol-cloud interactions; aerosol remote sensing
Dr. Gabriele Curci
E-Mail Website
Guest Editor
Department of Physical and Chemical Sciences, Università degli Studi dell’Aquila, 67010 Coppito, L’Aquila, Italy
Tel. +39-0862-433708
Interests: regional tropospheric chemistry and air quality; global and regional modeling of atmospheric aerosols and their radiative effects; aerosol-cloud interactions; intercontinental transport of trace gases and aerosols; aerosol optical properties and mixing state; aerosol remote sensing
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Aerosol particles have a central role in the radiation budget of the atmosphere, through a variety of processes, from direct scattering and absorption of solar and planetary radiation to indirect effects related to formation of cloud droplets and ice particles in the troposphere, or even in the stratospheric polar vortices. Other effects may play a substantial role in the atmospheric radiative transfer, as, for example, the aerosol deposition feedback on the albedo of snow/ice covered surfaces or the influence on atmospheric stability due to absorption of radiation. The aerosol distribution on global and regional scales is dependent on emission, removal and horizontal-vertical transport processes. A reliable estimate of the direct radiative effects can be reached if a good knowledge of the vertical distribution of the particles is reached, along with their size distribution and physical composition. A meaningful representation of the indirect effects needs to take several complex microphysical processes into account. As clearly stated in several IPCC reports and in scientific literature, the level of scientific understanding of these processes is often low or very low, and the range of uncertainty in the evaluation of their effect on weather and climate is significant. Consequently, a great deal of observational and modeling work is needed to better understand the uncertainties in the net radiative forcing of atmospheric aerosols.

Manuscripts on all aspects of the radiative effects of atmospheric aerosols are welcome for this Special Issue.

Dr. Giovanni Pitari
Dr. Gabriele Curci
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Atmosphere is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.


Keywords

  • Atmospheric aerosols
  • Direct radiative effects
  • Indirect radiative effects
  • Semi-direct radiative effects
  • Aerosol-cloud interactions
  • Aerosol transport
  • Aerosol vertical profiles
  • Aerosol chemical and physical properties
  • Aerosol measurements and modeling

Published Papers (15 papers)

Order results
Result details
Select all
Export citation of selected articles as:

Research

Open AccessArticle
Impact of Stratospheric Volcanic Aerosols on Age-of-Air and Transport of Long-Lived Species
Atmosphere 2016, 7(11), 149; https://doi.org/10.3390/atmos7110149 - 22 Nov 2016
Cited by 12
Abstract
The radiative perturbation associated to stratospheric aerosols from major explosive volcanic eruptions may induce significant changes in stratospheric dynamics. The aerosol heating rates warm up the lower stratosphere and cause a westerly wind anomaly, with additional tropical upwelling. Large scale transport of stratospheric [...] Read more.
The radiative perturbation associated to stratospheric aerosols from major explosive volcanic eruptions may induce significant changes in stratospheric dynamics. The aerosol heating rates warm up the lower stratosphere and cause a westerly wind anomaly, with additional tropical upwelling. Large scale transport of stratospheric trace species may be perturbed as a consequence of this intensified Brewer–Dobson circulation. The radiatively forced changes of the stratospheric circulation during the first two years after the eruption of Mt. Pinatubo (June 1991) may help explain the observed trend decline of long-lived greenhouse gases at surface stations (approximately −8 and −0.4 ppbv/year for CH4 and N2O, respectively). This decline is partly driven by the increased mid- to high-latitude downward flux at the tropopause and also by an increased isolation of the tropical pipe in the vertical layer near the tropopause, with reduced horizontal eddy mixing. Results from a climate-chemistry coupled model are shown for both long-lived trace species and the stratospheric age-of-air. The latter results to be younger by approximately 0.5 year at 30 hPa for 3–4 years after the June 1991 Pinatubo eruption, as a result of the volcanic aerosols radiative perturbation and is consistent with independent estimates based on long time series of in situ profile measurements of SF6 and CO2. Younger age of air is also calculated after Agung, El Chichón and Ruiz eruptions, as well as negative anomalies of the N2O growth rate at the extratropical tropopause layer. This type of analysis is made comparing the results of two ensembles of model simulations (1960–2005), one including stratospheric volcanic aerosols and their radiative interactions and a reference case where the volcanic aerosols do not interact with solar and planetary radiation. Full article
(This article belongs to the Special Issue Atmospheric Aerosols and Their Radiative Effects)
Show Figures

Graphical abstract

Open AccessArticle
Inversion of Nighttime PM2.5 Mass Concentration in Beijing Based on the VIIRS Day-Night Band
Atmosphere 2016, 7(10), 136; https://doi.org/10.3390/atmos7100136 - 19 Oct 2016
Cited by 7
Abstract
In order to monitor nighttime particular matter (PM) air quality in urban area, a back propagation neural network (BP neural network) inversion model is established, using low-light radiation data from the day/night band (DNB) of the Visible Infrared Imaging Radiometer Suite (VIIRS) aboard [...] Read more.
In order to monitor nighttime particular matter (PM) air quality in urban area, a back propagation neural network (BP neural network) inversion model is established, using low-light radiation data from the day/night band (DNB) of the Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the Suomi National Polar-orbiting Partnership (S-NPP) satellite. The study focuses on the moonless and cloudless nights in Beijing during March–May 2015. A test is carried out by selecting surface PM2.5 data from 12 PM2.5 automatic monitoring stations and the corresponding night city light intensity from DNB. As indicated by the results, the linear correlation coefficient (R) between the results and the corresponding measured surface PM2.5 concentration is 0.91, and the root-mean-square error (RMSE) is 14.02 μg/m3 with the average of 59.39 μg/m3. Furthermore, the BP neural network model shows better accuracy when air relative humility ranges from 40% to 80% and surface PM2.5 concentration exceeds 40 μg/m3. The study provides a superiority approach for monitoring PM2.5 air quality from space with visible light remote sensing data at night. Full article
(This article belongs to the Special Issue Atmospheric Aerosols and Their Radiative Effects)
Show Figures

Figure 1

Open AccessArticle
Retrieval of Aerosol Optical Depth over Arid Areas from MODIS Data
Atmosphere 2016, 7(10), 134; https://doi.org/10.3390/atmos7100134 - 16 Oct 2016
Cited by 6
Abstract
Moderate Resolution Imaging Spectroradiometer (MODIS) data have been widely applied for the remote sensing of aerosol optical depth (AOD) because the MODIS sensor features a short revisit period and a moderate spatial resolution. The Dense Dark Vegetation (DDV) method is the most [...] Read more.
Moderate Resolution Imaging Spectroradiometer (MODIS) data have been widely applied for the remote sensing of aerosol optical depth (AOD) because the MODIS sensor features a short revisit period and a moderate spatial resolution. The Dense Dark Vegetation (DDV) method is the most popular retrieval method. However, the DDV method can only be used to retrieve the AOD with high precision when the surface reflectance in the visible spectrum is low, such as over dense vegetation or water. To obtain precise AOD values in areas with higher reflectance, such as arid areas, Land Surface Reflectance (LSR) must be estimated accurately. This paper proposes a method of estimating LSR for AOD retrieval over arid areas from long-term series of MODIS images. According to the atmospheric parameters (AOD and water vapor), the clearest image without clouds was selected from the long-term series of continuous MODIS images. Atmospheric correction was conducted based on similar ground-measured atmospheric parameters and was used to estimate the LSR and retrieve the AOD at adjacent times. To validate this method, aerosol inversion experiments were performed in northern Xinjiang, in which the inverted AOD was compared to ground-measured AOD and MODIS aerosol products (MOD04). The AOD retrieved using the new algorithm was highly consistent with the AOD derived from ground-based measurements, with a correlation coefficient of 0.84. Additionally, 82.22% of the points fell within the expected error defined by NASA. The precision of the retrieved AOD data was better than that of MOD04 AOD products over arid areas. Full article
(This article belongs to the Special Issue Atmospheric Aerosols and Their Radiative Effects)
Show Figures

Figure 1

Open AccessArticle
Effect of the Aerosol Type Selection for the Retrieval of Shortwave Ground Net Radiation: Case Study Using Landsat 8 Data
Atmosphere 2016, 7(9), 111; https://doi.org/10.3390/atmos7090111 - 25 Aug 2016
Cited by 1
Abstract
This paper discusses the aerosol radiative effects involved in the accuracy of shortwave net radiation, R n . s w , with s w (400–900) nm, retrieved by the Operational Land Imager (OLI), the new generation sensor of the Landsat mission. Net [...] Read more.
This paper discusses the aerosol radiative effects involved in the accuracy of shortwave net radiation, R n . s w , with s w (400–900) nm, retrieved by the Operational Land Imager (OLI), the new generation sensor of the Landsat mission. Net radiation is a key parameter for the energy exchange between the land and atmosphere; thus, R n . s w retrieval from space is under investigation by exploiting the increased spatial resolution of the visible and near-infrared OLI data. We adopted the latest version of the Second Simulation of a Satellite Signal in the Solar Spectrum (6SV) atmospheric radiative transfer model implemented in the atmospheric correction algorithm (OLI Atmospherically-Corrected Reflectance Imagery ([email protected])) developed specifically for OLI data. The values of R n . s w were obtained by varying the microphysical properties of the aerosol during the [email protected] retrieval of both the OLI surface reflectance, ρ p x l o l i , and the incoming solar irradiance at the surface. The analysis of the aerosol effects on the R n . s w was carried out on a spectrally-homogeneous desert area located in the southwestern Nile Delta. The results reveal that the R n . s w available for energy exchange between the land and atmosphere reduces the accuracy (NRMSE ≃ 14%) when the local aerosol microphysical properties are not considered during the processing of space data. Consequently, these findings suggest that the aerosol type should be considered for variables retrieved by satellite observations concerning the energy exchange in the natural ecosystems, such as Photosynthetically-Active Radiation (PAR). This will also improve the accuracy of land monitoring and of solar energy for power generation when space data are used. Full article
(This article belongs to the Special Issue Atmospheric Aerosols and Their Radiative Effects)
Show Figures

Figure 1

Open AccessArticle
Seasonal Variation of Nitrate Concentration and Its Direct Radiative Forcing over East Asia
Atmosphere 2016, 7(8), 105; https://doi.org/10.3390/atmos7080105 - 10 Aug 2016
Cited by 6
Abstract
This study investigated the seasonal variation of nitrate concentration and its radiative forcing over East Asia by using an online-coupled regional climate model. Comparison with a series of in-situ observations from Acid Deposition Monitoring Network in East Asia (EANET) and China demonstrated a [...] Read more.
This study investigated the seasonal variation of nitrate concentration and its radiative forcing over East Asia by using an online-coupled regional climate model. Comparison with a series of in-situ observations from Acid Deposition Monitoring Network in East Asia (EANET) and China demonstrated a good skill of the model in reproducing the magnitude and seasonality of nitrate concentration across East Asia. It was found that nitrate concentration in Beijing and Tianjin exhibited the maximum in summer and the minimum in winter possibly due to stronger chemical oxidation and regional transport effect of larger emissions from the north China Plain in summer, whereas in most areas of East Asia, nitrate concentration was higher in winter and lower in summer, consistent with the seasonality of NOx emission. Surface nitrate concentration was higher over the lower reaches of the Yellow River, followed by the middle to lower reaches of the Yangtze River and portions of south China, and lower in Korean Peninsula and Japan. The annual mean surface nitrate concentration was predicted to be 2.9 μg·m−3 for East Asia and 8.5 μg·m−3 for east China. All-sky direct radiative forcing (DRF) due to nitrate at the top of the atmosphere (TOA) exhibited the largest forcing up to −7 W·m−2 over the lower reaches of the Yellow River, and lower forcing of ~−2 W·m−2 in the Korean Peninsula and Japan. Clear-sky DRF by nitrate reached the maximum in spring and the minimum in summer over both East Asia and east China, whereas DRF under all-sky condition showed its maximum in autumn, associated with seasonalities of nitrate column burden, relative humidity, and cloud effect. Annual mean all-sky DRFs at TOA were estimated to be −1.7 W·m−2 and −3.7 W·m−2 over East Asia and east China, respectively, significantly larger than global annual mean, suggesting the important role of nitrate aerosol in environment and climate change over East Asia. Full article
(This article belongs to the Special Issue Atmospheric Aerosols and Their Radiative Effects)
Show Figures

Figure 1

Open AccessArticle
Sulfate Aerosols from Non-Explosive Volcanoes: Chemical-Radiative Effects in the Troposphere and Lower Stratosphere
Atmosphere 2016, 7(7), 85; https://doi.org/10.3390/atmos7070085 - 23 Jun 2016
Cited by 9
Abstract
SO2 and H2S are the two most important gas-phase sulfur species emitted by volcanoes, with a global amount from non-explosive emissions of the order 10 Tg-S/yr. These gases are readily oxidized forming SO42− aerosols, which effectively scatter the [...] Read more.
SO2 and H2S are the two most important gas-phase sulfur species emitted by volcanoes, with a global amount from non-explosive emissions of the order 10 Tg-S/yr. These gases are readily oxidized forming SO42− aerosols, which effectively scatter the incoming solar radiation and cool the surface. They also perturb atmospheric chemistry by enhancing the NOx to HNO3 heterogeneous conversion via hydrolysis on the aerosol surface of N2O5 and Br-Cl nitrates. This reduces formation of tropospheric O3 and the OH to HO2 ratio, thus limiting the oxidation of CH4 and increasing its lifetime. In addition to this tropospheric chemistry perturbation, there is also an impact on the NOx heterogeneous chemistry in the lower stratosphere, due to vertical transport of volcanic SO2 up to the tropical tropopause layer. Furthermore, the stratospheric O3 formation and loss, as well as the NOx budget, may be slightly affected by the additional amount of upward diffused solar radiation and consequent increase of photolysis rates. Two multi-decadal time-slice runs of a climate-chemistry-aerosol model have been designed for studying these chemical-radiative effects. A tropopause mean global net radiative flux change (RF) of −0.23 W·m−2 is calculated (including direct and indirect aerosol effects) with a 14% increase of the global mean sulfate aerosol optical depth. A 5–15 ppt NOx decrease is found in the mid-troposphere subtropics and mid-latitudes and also from pole to pole in the lower stratosphere. The tropospheric NOx perturbation triggers a column O3 decrease of 0.5–1.5 DU and a 1.1% increase of the CH4 lifetime. The surface cooling induced by solar radiation scattering by the volcanic aerosols induces a tropospheric stabilization with reduced updraft velocities that produce ice supersaturation conditions in the upper troposphere. A global mean 0.9% decrease of the cirrus ice optical depth is calculated with an indirect RF of −0.08 W·m−2. Full article
(This article belongs to the Special Issue Atmospheric Aerosols and Their Radiative Effects)
Show Figures

Figure 1

Open AccessArticle
Stratospheric Aerosols from Major Volcanic Eruptions: A Composition-Climate Model Study of the Aerosol Cloud Dispersal and e-folding Time
Atmosphere 2016, 7(6), 75; https://doi.org/10.3390/atmos7060075 - 26 May 2016
Cited by 20
Abstract
Large explosive volcanic eruptions are capable of injecting considerable amounts of particles and sulfur gases above the tropopause, causing large increases in stratospheric aerosols. Five major volcanic eruptions after 1960 (i.e., Agung, St. Helens, El Chichón, Nevado del Ruiz and Pinatubo) [...] Read more.
Large explosive volcanic eruptions are capable of injecting considerable amounts of particles and sulfur gases above the tropopause, causing large increases in stratospheric aerosols. Five major volcanic eruptions after 1960 (i.e., Agung, St. Helens, El Chichón, Nevado del Ruiz and Pinatubo) have been considered in a numerical study conducted with a composition-climate coupled model including an aerosol microphysics code for aerosol formation and growth. Model results are compared between an ensemble of numerical simulations including volcanic aerosols and their radiative effects (VE) and a reference simulations ensemble (REF) with no radiative impact of the volcanic aerosols. Differences of VE-REF show enhanced diabatic heating rates; increased stratospheric temperatures and mean zonal westerly winds; increased planetary wave amplitude; and tropical upwelling. The impact on stratospheric upwelling is found to be larger when the volcanically perturbed stratospheric aerosol is confined to the tropics, as tends to be the case for eruptions which were followed by several months with easterly shear of the quasi-biennial oscillation (QBO), e.g., the Pinatubo case. Compared to an eruption followed by a period of westerly QBO, such easterly QBO eruptions are quite different, with meridional transport to mid- and high-latitudes occurring later, and at higher altitude, with a consequent decrease in cross-tropopause removal from the stratosphere, and therefore longer decay timescale. Comparing the model-calculated e-folding time of the volcanic aerosol mass during the first year after the eruptions, an increase is found from 8.1 and 10.3 months for El Chichón and Agung (QBO westerly shear), to 14.6 and 30.7 months for Pinatubo and Ruiz (QBO easterly shear). The corresponding e-folding time of the global-mean radiative flux changes goes from 9.1 and 8.0 months for El Chichón and Agung, to 28.7 and 24.5 months for Pinatubo and Ruiz. Full article
(This article belongs to the Special Issue Atmospheric Aerosols and Their Radiative Effects)
Show Figures

Figure 1

Open AccessArticle
Aerosol Optical Properties Based on Ground and Satellite Retrievals during a Serious Haze Episode in December 2015 over Beijing
Atmosphere 2016, 7(5), 70; https://doi.org/10.3390/atmos7050070 - 20 May 2016
Cited by 16
Abstract
An extreme haze event occurred in the Beijing area from 17 to 23 December 2015. Ground-based measurements and satellite observations during this event were used to further our understanding of the formation process of haze pollution and aerosol optical properties. The results suggest [...] Read more.
An extreme haze event occurred in the Beijing area from 17 to 23 December 2015. Ground-based measurements and satellite observations during this event were used to further our understanding of the formation process of haze pollution and aerosol optical properties. The results suggest that high relative humidity, poor diffusion conditions (low wind speed and stable stratification) and favorable secondary transformation conditions under the hygroscopic growth of aerosol and high emissions led to this serious haze episode. During the haze period, the daily average value was 1.15 and 0.42 for aerosol optical depth (AOD500nm) and columnar water-vapor (CWV, in cm), respectively. On 19 December, the correlation coefficient between CWV and AOD500nm was 0.91, indicating the effect of hygroscopic growth of fine-mode articles. The daily average values for Ångström exponent, fine-mode fraction, aerosol absorption optical depth, and Ångström absorption exponent were 1.19, 0.81, 0.11 and 1.47, respectively, which suggests that fine aerosol particles were dominant in the atmosphere and fine-mode particles were the dominant contributor to atmospheric extinction during the haze period. Moreover, it also reflects that there were more absorbing aerosol particles during the haze period. Compared with other polluted periods with a bimodal distribution, there was an obvious trimodal distribution on 19 December. There were three peaks at radii of about 0.1 μm, 0.5–0.8 μm and 4 μm. Satellite observations show that there was an obvious aerosol layer in the Beijing area during the haze period, concentrated at ground level to within 2 km in the upper layers. The types of aerosol were mainly composed of mixed pollution aerosols. Full article
(This article belongs to the Special Issue Atmospheric Aerosols and Their Radiative Effects)
Show Figures

Figure 1

Open AccessArticle
Sensitivity and Contribution of Organic Aerosols to Aerosol Optical Properties Based on Their Refractive Index and Hygroscopicity
Atmosphere 2016, 7(5), 65; https://doi.org/10.3390/atmos7050065 - 11 May 2016
Cited by 3
Abstract
Organic carbon (OC) accounts for a large fraction of particulate matter. Since many atmospheric organic compounds have different optical properties, it is difficult to determine the optical properties of OC accurately. In particular, hygroscopicity and light absorption of OC are important factors in [...] Read more.
Organic carbon (OC) accounts for a large fraction of particulate matter. Since many atmospheric organic compounds have different optical properties, it is difficult to determine the optical properties of OC accurately. In particular, hygroscopicity and light absorption of OC are important factors in understanding the aerosol optical properties. In this study, the sensitivity of organic carbon (OC) to aerosol optical properties was tested. Both the refractive index and the hygroscopicity of OC were considered. Based on the filter-based monthly averaged sampling measurement data from an intensive observation site in Seoul, Korea, the contribution of each component on the aerosol optical properties was estimated. The aerosol optical properties were simulated by combining the aerosol dynamic model for polydispersed aerosols with an optical properties model based on Mie code. The optical properties were compared with the AERONET Aerosol Optical Thickness (AOT) measurement data. In order to estimate the contribution of the light absorption and hygroscopicity of organic carbon (OC) on the optical properties of the aerosols, a sensitivity test was conducted with different imaginary refractive indices and OC hygroscopic growth factors. The results show that mass absorption efficiency can be fitted linearly as the imaginary refractive index increases. This means that one can estimate the mass absorption efficiency of OC as a function of the imaginary refractive index. The results also show that mass extinction and absorption efficiency decrease as the hygroscopic factor of OC increases because of the increase in water content. The contribution of OC to the mass extinction efficiency, however, depends on the chemical composition of other aerosol mixtures and hence, more comprehensive studies are required in this regard. Full article
(This article belongs to the Special Issue Atmospheric Aerosols and Their Radiative Effects)
Show Figures

Figure 1

Open AccessArticle
Aerosol Optical Properties over Beijing during the World Athletics Championships and Victory Day Military Parade in August and September 2015
Atmosphere 2016, 7(3), 47; https://doi.org/10.3390/atmos7030047 - 19 Mar 2016
Cited by 15
Abstract
A special period in Beijing from 6 August to 17 September 2015, during which the World Athletics Championships and Victory Day military parade took place, and which involved measures to restrict traffic and reduce factory emissions, was selected to analyze the aerosol optical [...] Read more.
A special period in Beijing from 6 August to 17 September 2015, during which the World Athletics Championships and Victory Day military parade took place, and which involved measures to restrict traffic and reduce factory emissions, was selected to analyze the aerosol optical properties and the impact of meteorological conditions on pollution levels. The study was based on AERONET observational and retrieval data, particulate matter measurements (TEOM 1405), meteorological data, and then the HYSPLIT model was used to analyze the pollution sources. The study period was divided into three sub-periods according to the different stages of implementation of the control measures, and the main conclusions can be summarized as follows. During the period in which the restrictive measures were applied, the air quality improved significantly, with the average value of the AOD being 0.34 ± 0.20, about 69% less than before. Meanwhile, the average Ångström exponent was about 9.5% higher than before, with an average value of 1.38 ± 0.25, indicating that the main pollutants were fine particles. Single scattering albedo decreased as wavelength increased, being higher than in the other two stages (mean value of 0.944 ± 0.045). This showed that the strong scattering capacity and absorption aerosol optical depth was at its lowest, at about 0.008 ± 0.009. The peaks of aerosol volume concentration in the fine and coarse mode were significantly reduced. Meteorological conditions also had a certain effect on the aerosol optical properties, with the blowing of clean and dry wind and the occurrence of precipitation contributing to the overall improvement in air quality. Full article
(This article belongs to the Special Issue Atmospheric Aerosols and Their Radiative Effects)
Show Figures

Figure 1

Open AccessArticle
Analysis of the Error in Retrievals of Aerosol Optical Properties from Sunphotometer Measurements of CARSNET Due to a Variety of Objective Factors
Atmosphere 2016, 7(1), 9; https://doi.org/10.3390/atmos7010009 - 13 Jan 2016
Cited by 7
Abstract
In situ observation of the aerosol optical properties is important to the validations of satellite and modeling results; however, the operational measurements can be affected by some objective factors. An experiment study has been performed in order to analyze the error in retrievals [...] Read more.
In situ observation of the aerosol optical properties is important to the validations of satellite and modeling results; however, the operational measurements can be affected by some objective factors. An experiment study has been performed in order to analyze the error in retrievals of aerosol optical properties from sunphotometer measurements caused by a variety of in situ objective factors. The standard instrument relative error analysis method was used to determine the relative error of aerosol optical depth (AOD) and Ångström exponent (AE) under the effects of five factors: spider web inside the collimator (F1); collimator bending (F2); dust inside the optical head (F3); incrustation scale inside the optical head (F4); and dust and incrustation scale inside the optical head (F5). The results showed that the five factors caused error for AOD retrieved at 1020, 870, 670 and 440 nm, with the maximum error occurring at 870 nm due to the more sensitive measurement signals. The error ranges of AOD derived from the direct solar measurements in the four bands were −0.34%–8.77%, −6.22%–9.68%, −0.05%–2.52%, −0.96%–3.48% and 5.42%–13.38% for F1, F2, F3, F4 and F5, respectively. The maximum error occurred under the influence of F5 with an average error value of 10%, while the minimum occurred owing to F3 with an average error value of 1%. All of the AEs retrieved from the experimental instruments were smaller than that from the reference instrument. The AE error values were 15.19%, 25.57%, 4.56%, 4.41% and 8.83% for F1, F2, F3, F4 and F5, respectively. The average AE retrieval error value was 11.7%. Full article
(This article belongs to the Special Issue Atmospheric Aerosols and Their Radiative Effects)
Show Figures

Figure 1

Open AccessArticle
On the Importance of Aerosol Composition for Estimating Incoming Solar Radiation: Focus on the Western African Stations of Dakar and Niamey during the Dry Season
Atmosphere 2015, 6(11), 1608-1632; https://doi.org/10.3390/atmos6111608 - 29 Oct 2015
Cited by 4
Abstract
The article investigates the impact of aerosol composition on the estimation of the downwelling surface shortwave flux (DSSF). This initiative forms part of the efforts to improve the DSSF distributed by the Land Surface Analysis Satellite Application Facility (LSA-SAF). This operational product assumes [...] Read more.
The article investigates the impact of aerosol composition on the estimation of the downwelling surface shortwave flux (DSSF). This initiative forms part of the efforts to improve the DSSF distributed by the Land Surface Analysis Satellite Application Facility (LSA-SAF). This operational product assumes invariant aerosol properties under clear sky conditions, which can be inaccurate for some regions of the world. This is the case of West Africa, where aerosol activity is not only highly variable due to frequent dust storms but also rich because of the coexistence of different aerosol species. This study was carried out over the West African stations of Dakar and Niamey, which represent different aerosol scenarios. Several dates during the dry season of 2006 were selected and classified into four different day types according to aerosol activity: standard, clean, mixture and dusty days. The diurnal evolution of DSSF and its direct and diffuse components were estimated for the selected dates by the current LSA-SAF algorithm and two other approaches using aerosol measurements from the Aerosol Robotic Network (AERONET) as input. The first alternative approach took the diurnal evolution of the total aerosol optical depth (AOD) into account, assuming a default desert aerosol type. Experiments with this method showed a significant improvement in the estimated DSSF compared to the current LSA-SAF algorithm. For example, root mean square error (RMSE) improved from 170 W/m2 to 50 W/m2 for dusty days in Dakar and from 73 W/m2 to 21 W/m2 for mixture days in Niamey. This improvement resulted from the consideration of a time-varying AOD, which accounted for the rapidly changing aerosol load for these two day types. The second alternative approach tested included consideration of the diurnal variation of the aerosol load and composition. Again, this was done using AERONET data on the fine and coarse aerosol modes, which may be associated with different sized dust particles, sea salt, or soot from biomass burning (depending on the date). This enhanced consideration of the aerosol composition greatly improved the estimation of the diffuse component of the DSSF, further reducing the RMSE during mixture days from 50 W/m2 to less than 10 W/m2. This improvement mainly came from consideration of the right scattering properties of the aerosol particles, which may be significantly different for each aerosol type. Full article
(This article belongs to the Special Issue Atmospheric Aerosols and Their Radiative Effects)
Show Figures

Figure 1

Open AccessArticle
Optical Properties of Fine Particulate Matter in Upper Silesia, Poland
Atmosphere 2015, 6(10), 1521-1538; https://doi.org/10.3390/atmos6101521 - 20 Oct 2015
Cited by 3
Abstract
Ambient particles whose aerodynamic diameters were not greater than 2.5 µm (fine fraction of Particulate Matter; PM2.5) and 1 µm (PM1; sub-fraction of PM2.5) were sampled at three sites in Upper Silesia (Poland): urban background site, rural [...] Read more.
Ambient particles whose aerodynamic diameters were not greater than 2.5 µm (fine fraction of Particulate Matter; PM2.5) and 1 µm (PM1; sub-fraction of PM2.5) were sampled at three sites in Upper Silesia (Poland): urban background site, rural background site, and urban traffic site. In total, 240 samples were collected between 2 August 2009 and 27 December 2010. The reflectance of the collected PM1 and PM2.5 samples was determined with a digital smoke stain reflectometer. The 24-h courses and seasonal changes of three determined optical parameters for PM1 and PM2.5 (absorption coefficient (a), mass absorption (σ), and mean light reflection coefficient (Rav)) were illustrated and discussed. The mean values of the regional background absorption coefficient (a) were 1.27 × 10−5 m−1 and 0.87 × 10−5 m−1 for PM2.5 and PM1, respectively. In Katowice (urban background), the mean absorption levels were 2.37 × 10−5 m−1 and 2.09 × 10−5 m−1 for PM2.5 and PM1, respectively. The highest values of the absorption coefficient for both PM fractions were found close to the highway (urban traffic site). In the heating season (winter), the absorption coefficient (a) for PM2.5 and PM1 increased significantly when compared with the non-heating season. The obtained results confirmed the thesis about the significant increase in the elemental PM2.5-bound carbon concentration caused by the intensified hard coal combustion in Upper Silesia in winter. Moreover, it turned out that the increase in the concentration of the PM2.5-bound sulphates was even higher, which resulted in the relative decrease of the elemental carbon content in this PM fraction in some areas. Consequently, the mass absorption value dropped there as well. Full article
(This article belongs to the Special Issue Atmospheric Aerosols and Their Radiative Effects)
Show Figures

Figure 1

Open AccessArticle
Long-Term Trend and Seasonal Variability of Horizontal Visibility in Nigerian Troposphere
Atmosphere 2015, 6(10), 1462-1486; https://doi.org/10.3390/atmos6101462 - 02 Oct 2015
Cited by 7
Abstract
A study of the long-term variability; trend and characteristics of visibility in four zones of Nigeria was carried out. Visibility and other meteorological data from NOAA-NCDC and aerosol index data over Nigeria during 1984–2013 are analyzed using time series and simple regression model. [...] Read more.
A study of the long-term variability; trend and characteristics of visibility in four zones of Nigeria was carried out. Visibility and other meteorological data from NOAA-NCDC and aerosol index data over Nigeria during 1984–2013 are analyzed using time series and simple regression model. There are significant decreasing trends for every region and season during the 30-years period; the fluctuations exhibited nearly similar pattern. The 30-year mean visibilities for the four zones (Sahel; North Central; Southern; and Coastal) were 13.8 ± 3.9; 14.3 ± 4.2; 13.6 ± 3.5 and 12.8 ± 3.1 km with decreasing trends at the rates of 0.08; 0.06; 0.02 and 0.02 km/year. In all the zones; visibilities were better in summer while worse in Harmattan (dry season). During summer visibility was best in Sahel and North-central; however; in Harmattan visibility was best in southern and coastal zones. It was best between May and June (17.6; 18.9; 16.6 and 15.1 km) with a second peak in September. The 30-year seasonal averages were 16.2 ± 2.1; 16.8 ± 2.4; 15.4 ± 1.8 and 14.0 ± 2.2 km in summer; and 10.2 ± 2.5; 10.9 ± 2.9; 11.0 ± 3.3 and 11.4 ± 3.0 km in Harmattan for the respective zones. Sahel and North Central had the worse visibility reduction during Harmattan compared with Southern and coastal areas. An analysis based on simple regression equation reveals a strong and negative relationship between visibility on one hand; AI; and AOD on the other hand. The analysis also discusses the variability regarding the frequency of occurrence of a dust storm; dust haze; and good visibility over the period of study. Full article
(This article belongs to the Special Issue Atmospheric Aerosols and Their Radiative Effects)
Show Figures

Figure 1

Open AccessArticle
Estimation of the PM2.5 Pollution Levels in Beijing Based on Nighttime Light Data from the Defense Meteorological Satellite Program-Operational Linescan System
Atmosphere 2015, 6(5), 607-622; https://doi.org/10.3390/atmos6050607 - 12 May 2015
Cited by 6
Abstract
Nighttime light data record the artificial light on the Earth’s surface and can be used to estimate the degree of pollution associated with particulate matter with an aerodynamic diameter of less than 2.5 μm (PM2.5) in the ground-level atmosphere. This study [...] Read more.
Nighttime light data record the artificial light on the Earth’s surface and can be used to estimate the degree of pollution associated with particulate matter with an aerodynamic diameter of less than 2.5 μm (PM2.5) in the ground-level atmosphere. This study proposes a simple method for monitoring PM2.5 concentrations at night by using nighttime light imagery from the Defense Meteorological Satellite Program-Operational Linescan System (DMSP-OLS). This research synthesizes remote sensing and geographic information system techniques and establishes a back propagation neural-network (BP network) model. The BP network model for nighttime light data performed well in estimating the PM2.5 pollution in Beijing. The correlation coefficient between the BP network model predictions and the corrected PM2.5 concentration was 0.975; the root mean square error was 26.26 μg/m3, with a corresponding average PM2.5 concentration of 155.07 μg/m3; and the average accuracy was 0.796. The accuracy of the results primarily depended on the method of selecting regions in the DMSP nighttime light data. This study provides an opportunity to measure the nighttime environment. Furthermore, these results can assist government agencies in determining particulate matter pollution control areas and developing and implementing environmental conservation planning. Full article
(This article belongs to the Special Issue Atmospheric Aerosols and Their Radiative Effects)
Show Figures

Figure 1

Back to TopTop