scholarly journals Validation of aerosol optical depth and climatology of aerosol vertical distribution in the Taklimakan Desert

2015 ◽  
Vol 6 (2) ◽  
pp. 239-244 ◽  
Author(s):  
Xuemei Zong ◽  
Xiangao Xia ◽  
Huizheng Che
Keyword(s):  
Vertical Distribution ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Taklimakan Desert ◽  
The Taklimakan Desert

scholarly journals Aerosol optical depth (AOD): spatial and temporal variations and association with meteorological covariates in Taklimakan desert, China

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e10542
Author(s):  
Jinglong Li ◽  
Xiangyu Ge ◽  
Qing He ◽  
Alim Abbas
Keyword(s):  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Environmental Variables ◽  
Vegetation Index ◽  
Meteorological Factors ◽  
Meteorological Data ◽  
Detection Methods ◽  
Taklimakan Desert ◽  
The Taklimakan Desert ◽  
Modis Aod

Aerosol optical depth (AOD) is a key parameter that reflects aerosol characteristics. However, research on the AOD of dust aerosols and various environmental variables is scarce. Therefore, we conducted in-depth studies on the distributions and variations of AOD in the Taklimakan Desert and its margins, China. We examined the correlation characteristics between AOD and meteorological factors combined with satellite remote sensing detection methods using MCD19A2-MODIS AOD products (from 2000, 2005, 2010, and 2015), MOD13Q1-MODIS normalized difference vegetation index products, and meteorological data. We analyzed the temporal and spatial distributions of AOD, periodic change trends, and important impacts of meteorological factors on AOD in the Taklimakan Desert and its margins. To explore the relationships between desert aerosols and meteorological factors, a random forest model was used along with environmental variables to predict AOD and rank factor contributions. Results indicated that the monthly average AOD exhibited a clear unimodal curve that reached its maximum in April. The AOD values followed the order spring (0.28) > summer (0.27) > autumn (0.18) > winter (0.17). This seasonality is clear and can be related to the frequent sandstorms occurring in spring and early summer. Interannual AOD showed a gradually increasing trend to 2010 then large changes to 2015. AOD tends to increase from south to north. Based on the general trend, the maximum value of AOD is more dispersed and its low-value area is always stable. The climatic index that has the most significant effect on AOD is relative humidity.

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

<p>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.</p><p>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.</p><p>A broad distribution of particle sizes was consistently observed, with a significant giant mode up to 80 µm, 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).</p><p>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.</p><p>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.</p>

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.

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.

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