Comments to "Intra-annual variations of regional aerosol optical depth, vertical distribution, and particle types from multiple satellite and ground-based observational datasets"

2018 ◽  
Author(s):  
Anonymous
Keyword(s):  
Vertical Distribution ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Annual Variations

scholarly journals Intra-annual variations of regional aerosol optical depth, vertical distribution, and particle types from multiple satellite and ground-based observational datasets

2018 ◽  
Author(s):  
Bin Zhao ◽  
Jonathan H. Jiang ◽  
David J. Diner ◽  
Hui Su ◽  
Yu Gu ◽  
...  
Keyword(s):  
Vertical Distribution ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Fine Particles ◽  
Seasonal Pattern ◽  
Diurnal Variations ◽  
Central China ◽  
Dominant Type ◽  
Annual Variations ◽  
Seasonal And Diurnal Variations

Abstract. The relatively short lifetimes of aerosols in the atmosphere result in climatic and health effects that are strongly dependent on intra-annual variations in particle concentrations. While many studies have examined the seasonal and diurnal variations of regional aerosol optical depth (AOD), understanding the temporal variations in aerosol vertical distribution and particle types is also important for accurate computation of aerosol radiative effects. In this paper, we combine the observations from four satellite-borne sensors and ground-based AOD and fine particle (PM2.5) measurements to investigate the seasonal and diurnal variations of aerosol column loading, vertical distribution, and particle types over three populous regions: the Eastern United States (EUS), Western Europe (WEU), and Eastern and Central China (ECC). In all three regions, column AOD, as well as AOD higher than 800 m above ground level, peaks in summer/spring probably due to accelerated formation of secondary aerosols and hygroscopic growth. However, AOD at height below 800 m mostly peaks in winter except that a second maximum in summer occurs over the EUS region, which is consistent with observed temporal trends in surface PM2.5 concentrations. AOD due to fine particles ( 1.4 μm diameter) generally shows less variability, except for the ECC region where a peak occurs in spring, consistent with the prevalence of airborne dust during this season. When aerosols are classified according to sources, the dominant type is associated with anthropogenic air pollution, which has a similar seasonal pattern as total AOD. Dust and sea-spray aerosols in the WEU region peak in summer and winter, respectively, but do not show an obvious seasonal pattern in the EUS region. Smoke aerosols, as well as absorbing aerosols, present an obvious unimodal distribution with a maximum occurring in summer over the EUS and WEU regions, whereas they follow a bimodal distribution with peaks in August and March (due to crop residue burning) over the ECC region. In general, the nighttime-daytime AOD difference is more positive in summer than in winter, likely attributable to a larger diurnal temperature range in summer. Smoke AOD is much higher in the nighttime than in the daytime. The results of this study can help to improve the current estimates of the climatic and health impacts of aerosols.

scholarly journals Intra-annual variations of regional aerosol optical depth, vertical distribution, and particle types from multiple satellite and ground-based observational datasets

2018 ◽  
Vol 18 (15) ◽  
pp. 11247-11260 ◽  
Author(s):  
Bin Zhao ◽  
Jonathan H. Jiang ◽  
David J. Diner ◽  
Hui Su ◽  
Yu Gu ◽  
...  
Keyword(s):  
Vertical Distribution ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Seasonal Variations ◽  
Fine Particles ◽  
Seasonal Pattern ◽  
Temporal Trends ◽  
Central China ◽  
Dominant Type ◽  
Annual Variations

Abstract. The climatic and health effects of aerosols are strongly dependent on the intra-annual variations in their loading and properties. While the seasonal variations of regional aerosol optical depth (AOD) have been extensively studied, understanding the temporal variations in aerosol vertical distribution and particle types is also important for an accurate estimate of aerosol climatic effects. In this paper, we combine the observations from four satellite-borne sensors and several ground-based networks to investigate the seasonal variations of aerosol column loading, vertical distribution, and particle types over three populous regions: the Eastern United States (EUS), Western Europe (WEU), and Eastern and Central China (ECC). In all three regions, column AOD, as well as AOD at heights above 800 m, peaks in summer/spring, probably due to accelerated formation of secondary aerosols and hygroscopic growth. In contrast, AOD below 800 m peaks in winter over WEU and ECC regions because more aerosols are confined to lower heights due to the weaker vertical mixing. In the EUS region, AOD below 800 m shows two maximums, one in summer and the other in winter. The temporal trends in low-level AOD are consistent with those in surface fine particle (PM2.5) concentrations. AOD due to fine particles (<0.7 µm diameter) is much larger in spring/summer than in winter over all three regions. However, the coarse mode AOD (>1.4 µm diameter), generally shows small variability, except that a peak occurs in spring in the ECC region due to the prevalence of airborne dust during this season. When aerosols are classified according to sources, the dominant type is associated with anthropogenic air pollution, which has a similar seasonal pattern as total AOD. Dust and sea-spray aerosols in the WEU region peak in summer and winter, respectively, but do not show an obvious seasonal pattern in the EUS region. Smoke aerosols, as well as absorbing aerosols, present an obvious unimodal distribution with a maximum occurring in summer over the EUS and WEU regions, whereas they follow a bimodal distribution with peaks in August and March (due to crop residue burning) over the ECC region.

Is aerosol optical depth a good metric to map dust properties? Lessons learned from AER-D

2020 ◽  
Author(s):  
Franco Marenco ◽  
Claire Ryder ◽  
Victor Estelles ◽  
Debbie O'Sullivan
Keyword(s):  
Remote Sensing ◽  
Particle Size ◽  
Vertical Distribution ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Field Experiments ◽  
Saharan Air Layer ◽  
Validation Experiment ◽  
Operational Models ◽  
The Vertical Distribution

&lt;p&gt;The main observable quantity used on a global scale to map aerosols is aerosol optical depth (AOD), from ground-based and satellite remote sensing. It is at the same time an optical property and a vertically integrated quantity, and it is commonly used as the main metric towards which to pull aerosol models, through data assimilation, verification, and tuning. Here we introduce a few reflections on how to better constrain our knowledge of the Saharan Air Layer and its associated mineral dust, following results from the AER-D campaign.&lt;/p&gt;&lt;p&gt;AER-D was a small field experiment in the Eastern Atlantic during August 2015, based on the opportunity given by the simultaneous ICE-D experiment. The purpose of AER-D was to investigate the physical properties of the Saharan Air Layer, and to assess and validate remote sensing and modelling products. The FAAM atmospheric research aircraft was used as a flying laboratory, and it carried a full set of instruments aimed at both in-situ sampling and remote sensing.&lt;/p&gt;&lt;p&gt;A broad distribution of particle sizes was consistently observed, with a significant giant mode up to 80 &amp;#181;m, generally larger than what was observed in previous experiments: we ascribe this to the set of instruments used, able to capture the full spectrum. We will discuss the representation of the particle size in operational models, and we will show that despite predicting an extinction coefficient of the correct order of magnitude, the particle size is generally underestimated. We will also discuss the implication of the giant particles for the ground-based remote sensing of columnar size-distributions from the SKYNET and AERONET networks (Sunphotometer Airborne Validation Experiment, which was a component of AER-D).&lt;/p&gt;&lt;p&gt;We will present the vertical structure of the Saharan Air Layer, and in particular one episode when the structure was very different than the one generally accepted in the conceptual model. Moreover, the comparison with the operational models showed that they can predict a correct aerosol optical depth (AOD, a vertically integrated quantity) despite missing the vertical distribution.&lt;/p&gt;&lt;p&gt;These findings lead to a series of reflections on how to better constrain our knowledge of the Saharan Air Layer and its representation in operational models. Size-resolved properties and the vertical distribution are essential companions of the global AOD observations commonly used operationally. We will also discuss objectives and ideas for future field experiments.&lt;/p&gt;

scholarly journals Climatological Aspects of Aerosol Physical Characteristics in Tunisia Deduced from Sun Photometric Measurements

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Mabrouk Chaâbane ◽  
Chafai Azri ◽  
Khaled Medhioub
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Climatic Data ◽  
Weather Patterns ◽  
Annual Variations ◽  
Microphysical Properties ◽  
Atmospheric Turbidity ◽  
Long Time ◽  
Photometric Measurements ◽  
Aerosol Emissions

Atmospheric and climatic data measured at Thala site (Tunisia) for a long-time period (1977–2001) are used to analyse the monthly, seasonal, and annual variations of the aerosol optical depth at 1 μm wavelength. We have shown that aerosol and microphysical properties and the dominating aerosol types depend on seasons. A comparison of the seasonal cycle of aerosol optical characteristics at Thala site showed that the contribution of long-range transported particles is expected to be larger in summer as a consequence of the weather stability typical of this season. Also, the winter decrease in atmospheric turbidity may result from increases in relative humidity and decreases in temperature, leading to increased particle size and mass and increased fall and deposition velocities. The spring and autumn weather patterns usually carry fine dust and sand particles for the desert area to Thala region. The annual behaviour of the aerosol optical depth recorded a period of stead increase started in 1986 until 2001. Trends in atmospheric turbidity after 1988 could be explained other ways by the contribution of the eruption of Mount Pinatubo in 1991 and by local or regional changes in climate or in aerosol emissions.

scholarly journals Vertical distribution of the spectral aerosol optical depth in the Arctic from 1993 to 1996

1998 ◽  
Vol 103 (D2) ◽  
pp. 1857-1870 ◽  
Author(s):  
Dagmar Nagel ◽  
Andreas Herber ◽  
Larry W. Thomason ◽  
Ullrich Leiterer
Keyword(s):  
Vertical Distribution ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
The Arctic

scholarly journals Impact of Aerosol Vertical Distribution on Aerosol Optical Depth Retrieval from Passive Satellite Sensors

2020 ◽  
Vol 12 (9) ◽  
pp. 1524 ◽  
Author(s):  
Chong Li ◽  
Jing Li ◽  
Oleg Dubovik ◽  
Zhao-Cheng Zeng ◽  
Yuk L. Yung
Keyword(s):  
Vertical Distribution ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Vertical Profile ◽  
Retrieval Algorithm ◽  
Retrieval Error ◽  
Satellite Sensors ◽  
Absorbing Aerosols ◽  
The Impact ◽  
The Vertical Distribution

When retrieving Aerosol Optical Depth (AOD) from passive satellite sensors, the vertical distribution of aerosols usually needs to be assumed, potentially causing uncertainties in the retrievals. In this study, we use the Moderate Resolution Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) sensors as examples to investigate the impact of aerosol vertical distribution on AOD retrievals. A series of sensitivity experiments was conducted using radiative transfer models with different aerosol profiles and surface conditions. Assuming a 0.2 AOD, we found that the AOD retrieval error is the most sensitive to the vertical distribution of absorbing aerosols; a −1 km error in aerosol scale height can lead to a ~30% AOD retrieval error. Moreover, for this aerosol type, ignoring the existence of the boundary layer can further result in a ~10% AOD retrieval error. The differences in the vertical distribution of scattering and absorbing aerosols within the same column may also cause −15% (scattering aerosols above absorbing aerosols) to 15% (scattering aerosols below absorbing aerosols) errors. Surface reflectance also plays an important role in affecting the AOD retrieval error, with higher errors over brighter surfaces in general. The physical mechanism associated with the AOD retrieval errors is also discussed. Finally, by replacing the default exponential profile with the observed aerosol vertical profile by a micro-pulse lidar at the Beijing-PKU site in the VIIRS retrieval algorithm, the retrieved AOD shows a much better agreement with surface observations, with the correlation coefficient increased from 0.63 to 0.83 and bias decreased from 0.15 to 0.03. Our study highlights the importance of aerosol vertical profile assumption in satellite AOD retrievals, and indicates that considering more realistic profiles can help reduce the uncertainties.

Inter-annual variations of the aerosol optical depth of the atmosphere at the Mirny Antarctic Observatory

2021 ◽  
Author(s):  
Dmitry M. Kabanov ◽  
Ivan A. Kruglinsky ◽  
Vladimir F. Radionov ◽  
Grigory E. Ryabkov ◽  
Sergey M. Sakerin
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Annual Variations
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