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Intercomparison of aerosol single-scattering albedo derived from AERONET surface radiometers and LARGE in situ aircraft profiles during the 2011 DRAGON-MD and DISCOVER-AQ experiments
摘要： Single-scattering albedo (SSA) retrievals obtained with CIMEL Sun-sky radiometers from the Aerosol Robotic Network (AERONET) aerosol monitoring network were used to make comparisons with simultaneous in situ sampling from aircraft profiles carried out by the NASA Langley Aerosol Group Experiment (LARGE) team in the summer of 2011 during the coincident DRAGON-MD (Distributed Regional Aerosol Gridded Observational Network-Maryland) and DISCOVER-AQ (Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality) experiments. The single-scattering albedos (interpolated to 550 nm) derived from AERONET measurements for aerosol optical depth (AOD) at 440 nm ≥ 0.4 (mean SSA: 0.979) were on average 0.011 lower than the values derived from the LARGE profile measurements (mean SSA: 0.99). The maximum difference observed was 0.023 with all the observed differences within the combined uncertainty for the stated SSA accuracy (0.03 for AERONET; 0.02 for LARGE). Single-scattering albedo averages were also analyzed for lower aerosol loading conditions (AOD ≥ 0.2) and a dependence on aerosol optical depth was noted with significantly lower single-scattering albedos observed for lower AOD in both AERONET and LARGE data sets. Various explanations for the SSA trend were explored based on other retrieval products including volume median radius and imaginary refractive index as well as column water vapor measurements. Additionally, these SSA trends with AOD were evaluated for one of the DRAGON-MD study sites, Goddard Space Flight Center, and two other Mid-Atlantic AERONET sites over the long-term record dating to 1999.
关键词： aerosol,DRAGON-MD,LARGE,single-scattering albedo,DISCOVER-AQ,AERONET
更新于2025-09-23 15:22:29
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Quantification of uncertainty in aerosol optical thickness retrieval arising from aerosol microphysical model and other sources, applied to Ozone Monitoring Instrument (OMI) measurements
摘要： Satellite instruments are nowadays successfully utilised for measuring atmospheric aerosol in many applications as well as in research. Therefore, there is a growing need for rigorous error characterisation of the measurements. Here, we introduce a methodology for quantifying the uncertainty in the retrieval of aerosol optical thickness (AOT). In particular, we concentrate on two aspects: uncertainty due to aerosol microphysical model selection and uncertainty due to imperfect forward modelling. We apply the introduced methodology for aerosol optical thickness retrieval of the Ozone Monitoring Instrument (OMI) on board NASA's Earth Observing System (EOS) Aura satellite, launched in 2004. We apply statistical methodologies that improve the uncertainty estimates of the aerosol optical thickness retrieval by propagating aerosol microphysical model selection and forward model error more realistically. For the microphysical model selection problem, we utilise Bayesian model selection and model averaging methods. Gaussian processes are utilised to characterise the smooth systematic discrepancies between the measured and modelled reflectances (i.e. residuals). The spectral correlation is composed empirically by exploring a set of residuals. The operational OMI multi-wavelength aerosol retrieval algorithm OMAERO is used for cloud-free, over-land pixels of the OMI instrument with the additional Bayesian model selection and model discrepancy techniques introduced here. The method and improved uncertainty characterisation is demonstrated by several examples with different aerosol properties: weakly absorbing aerosols, forest fires over Greece and Russia, and Sahara desert dust. The statistical methodology presented is general; it is not restricted to this particular satellite retrieval application.
关键词： OMI,Gaussian processes,OMAERO,uncertainty quantification,Bayesian model selection,aerosol optical thickness
更新于2025-09-23 15:22:29
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Integrated Aerosol Extinction Profiles from Ceilometer and Sunphotometer Combination against Sunphotometer Measurements at Various Heights
摘要： The aerosol extinction profiles at Granada (Spain) have been obtained combining ceilometer and sun/sky measurements in the GRASP code. In order to see the goodness of these retrieved profiles, three photometers at different altitudes have been used. The aerosol optical depth (AOD) at different height layers have been calculated with these photometers and it has been compared against the integrated retrieved extinction at the same layers. The obtained AOD (from GRASP and from photometers at different altitudes) correlates well, showing the most of r2 values above 0.6. The differences between both AOD values indicates that the retrieved aerosol extinction profiles are within the uncertainty of the photometers but this method overestimates the extinction at low levels and underestimates at high levels.
关键词： Validation,GRASP,Aerosol Optical Depth,Aerosol Extinction,Ceilometer
更新于2025-09-23 15:21:21
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Aerosol Retrieval in the Autumn and Winter From the Red and 2.12 μm Bands of MODIS
摘要： In the autumn and winter, aerosol is the important atmospheric pollutant over the Beijing–Tianjin–Hebei region. For monitoring aerosol in the autumn and winter, the lack of vegetation and the aging of MODIS sensor are two problems that needed to be solved. In this paper, after analyzing the characteristics of aerosol radiance in the red and shortwave infrared (2.12 μm) bands of MODIS, we develop a new algorithm for terrestrial aerosol with the assumption that the re?ectance ratio between the red and 2.12 μm bands is invariant. With MODIS data over the Beijing–Tianjin–Hebei region from September 2016 to February 2017, the algorithm is applied to aerosol retrieval. The retrieved aerosol optical depth images show that our algorithm can retrieve aerosol over sparse vegetation, and the validation with the AERONET/PHOTONS Beijing site shows that the correlation is greater than 0.9% and 77% of the retrievals fall within the expected error. An error analysis shows that a 2% error in the proportion of the soot component can lead to 15% retrieval error, and over more than 60% of the surface area, the error from the changes in the ratio between the red and 2.12 μm bands can lead to retrieved errors less than 0.1.
关键词： infrared measurements,remote sensing,Aerosol,atmospheric measurements
更新于2025-09-23 15:21:21
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Machine learning for improved data analysis of biological aerosol using the WIBS
摘要： Primary biological aerosol including bacteria, fungal spores and pollen have important implications for public health and the environment. Such particles may have different concentrations of chemical fluorophores and will respond differently in the presence of ultraviolet light, potentially allowing for different types of biological aerosol to be discriminated. Development of ultraviolet light induced fluorescence (UV-LIF) instruments such as the Wideband Integrated Bioaerosol Sensor (WIBS) has allowed for size, morphology and fluorescence measurements to be collected in real-time. However, it is unclear without studying instrument responses in the laboratory, the extent to which different types of particles can be discriminated. Collection of laboratory data is vital to validate any approach used to analyse data and ensure that the data available is utilized as effectively as possible.
关键词： biological aerosol,UV-LIF,WIBS,clustering,machine learning
更新于2025-09-23 15:21:21
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An Evaluation of MODIS-Retrieved Aerosol Optical Depth over AERONET Sites in Alaska
摘要： The air quality monitoring network in Alaska is currently limited to ground-based observations in urban areas and national parks, leaving a large proportion of the state unmonitored. The use of Moderate Resolution Imaging Spectroradiometer MODIS aerosol optical depth (AOD) to estimate ground-level particulate pollution concentrations has been successfully demonstrated around the world and could potentially be used in Alaska. In this work, MODIS AOD measurements at 550 nm were validated against AOD derived from two ground-based Aerosol Robotic Network (AERONET) sunphotometers in Alaska, located at Utqiagvik (previously known as Barrow) and Bonanza Creek, to determine if MODIS AOD from the Terra and Aqua satellites could be used to estimate ground-level particulate pollution concentrations. The MODIS AOD was obtained from MODIS collection 6 using the dark target Land and Ocean algorithms from years 2000 to 2014. MODIS data could only be obtained between the months of April and October; therefore, it was only evaluated for those months. Individual and combined Terra and Aqua MODIS data were considered. The results showed that MODIS collection 6 products at 10-km resolution for Terra and Aqua combined are not valid over land but are valid over the ocean. Note that the individual Terra and Aqua MODIS collection 6 AOD products at 10-km resolution are valid over land individually but not when combined. Results also suggest the MODIS collection 6 AOD products at 3-km resolution are valid over land and ocean and perform better over land than the 10-km product. These findings indicate that MODIS collection 6 AOD products can be used quantitatively in air quality applications in Alaska during the summer months.
关键词： Alaska,Aerosol Optical Depth,Moderate Resolution Imaging Spectroradiometer,Aerosol Robotic Network,air quality
更新于2025-09-23 15:21:01
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Molecular Insights into NO-Promoted Sulfate Formation on Model TiO <sub/>2</sub> Nanoparticles with Different Exposed Facets
摘要： In this study, molecular insights into NO-promoted SO2 oxidation on model TiO2 with well-defined (001), (010) and (101) facets are investigated in laboratory. The adsorbed SO2 is significantly promoted to transform into sulfate by the coexisting NO on the three facets. The appearance of active oxygen species indicates an active oxygen species-initiated NO oxidation. The resulting NO2 acts as an oxidant to convert adsorbed sulfite on hydroxyls to sulfate species. The (101) facet presents the best performance in the NO-promoted sulfate formation possibly owing to its desirable structure to accommodate SO3 2-, NO2 and molecular water. The uptake coefficient (γt) of SO2 increases by the coexistence of NO on (001) facet at 0% RH, and is relative humidity (RH) dependent, which first decreases from 0% RH to 32% RH but then increases in the range of 32% - 80% RH. The probable explanation is the combined contribution of the blocking effect of water and the hydration of SO2. The finding in this study provide an insight into the possibility of its occurrence on common mineral dusts and requires further investigation.
关键词： NO-promoted sulfate formation,sulfate aerosol,heterogeneous reaction,mineral dust,TiO2 nanoparticles
更新于2025-09-23 15:21:01
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Aerosol Jet Printed Optical Waveguides for Short Range Communication
摘要： This article presents an innovative way for additive manufacturing of optical multimode waveguides for short range data transmission. By the use of aerosol jet printing between conditioning lines on flexible foils, low cost and low weight polymer optical waveguides can be easily fabricated. The main advantages – compared to other waveguide manufacturing techniques – are the maximum fabricable waveguide length (not limited by panel- or wafer size), technology costs and 3D-ability. Furthermore, the printing allows for very long structures, which are not limited to wafer or panel sizes. In order to classify the new manufacturing approach and compare it to other technologies such as photolithography, imprinting, dispensing and ion-exchange, results on the mechanical (shear strength) and optical performance (transmittance, near field and attenuation) are presented. In addition, the experimental results on the data transmission performance are important to prove the suitability of the waveguides for high-speed communication applications. In this context, nearly error-free transmission up to 10 Gbit/s was achieved at a wavelength of 850 nm.
关键词： optical multimode waveguide,additive manufacturing,shear test,aerosol jet printing,optical data transmission
更新于2025-09-23 15:21:01
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Improved Two-wavelength Lidar algorithm for Retrieving Atmospheric Boundary Layer Height
摘要： The atmospheric boundary layer height (BLH) is a critical parameter for the spread and dispersion of atmospheric pollutants. We propose an improved two-wavelength Lidar algorithm for retrieving the BLH based on particle clustering. The algorithm was improved from two aspects: sample sequence selection and classifier optimisation. The backscatter coefficient and color ratio were chosen for the sample sequence construction, and Gaussian mixture models were used for the sample sequence classification. The improved method was tested on different real cases and compared with radiosonde measurements. The experimental results demonstrated the viability of the algorithm under weak mixing conditions, which can be problematic for prior methods. In addition, Lidar data from June 2015 to June 2016 were collected to investigate the stability of the improved method. The correlation between the BLH retrieved using the improved algorithm and that from the radiosonde measurements was R2 = 0.92, with an RMSE of 170 m. The correlation between the two-wavelength Lidar algorithm and radiosonde measurements was R2 = 0.82, with an RMSE of 180 m. The results show that the improved algorithm can obtain the BLH effectively and stability.
关键词： Color ratio,Lidar,Atmospheric boundary layer,Aerosol detection,Radiosonde
更新于2025-09-23 15:21:01
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Aerosol optical and microphysical retrievals from a hybrid multiwavelength lidar data set – DISCOVER-AQ 2011
摘要： Retrievals of aerosol microphysical properties (effective radius, volume and surface-area concentrations) and aerosol optical properties (complex index of refraction and single-scattering albedo) were obtained from a hybrid multiwavelength lidar data set for the first time. In July 2011, in the Baltimore–Washington DC region, synergistic profiling of optical and microphysical properties of aerosols with both airborne (in situ and remote sensing) and ground-based remote sensing systems was performed during the first deployment of DISCOVER-AQ. The hybrid multiwavelength lidar data set combines ground-based elastic backscatter lidar measurements at 355 nm with airborne High-Spectral-Resolution Lidar (HSRL) measurements at 532 nm and elastic backscatter lidar measurements at 1064 nm that were obtained less than 5 km apart from each other. This was the first study in which optical and microphysical retrievals from lidar were obtained during the day and directly compared to AERONET and in situ measurements for 11 cases. Good agreement was observed between lidar and AERONET retrievals. Larger discrepancies were observed between lidar retrievals and in situ measurements obtained by the aircraft and aerosol hygroscopic effects are believed to be the main factor in such discrepancies.
关键词： aerosol,lidar,DISCOVER-AQ,microphysical properties,optical properties
更新于2025-09-23 15:21:01