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Noise reduction and retrieval by modified lidar inversion method combines joint retrieval method and machine learning
摘要： To address the problem in which the signal-to-noise ratio of a raw atmospheric lidar signal decreases rapidly as the range increases, which has a tremendous effect on the accuracy and the effective range of lidar retrieval, many de-noising algorithms have been proposed. Among these methods, those based on the ensemble Kalman Filter (EnKF) exhibit good performance. EnKF-based methods can simultaneously denoise lidar signals and yield accurate retrieval results. However, due to poor forecasting in the EnKF step, biases exist in the results of these methods. In this study, a modified lidar inversion method was proposed for horizontal aerosol characteristic retrieval, which combines the joint retrieval method and Gaussian processing machine learning. This method compensates for the poor forecasting in the EnKF step in the joint retrieval method through the Gaussian processing machine learning algorithm, which can reduce the biases in the retrieval results. The modified lidar inversion method was applied to both simulated and real lidar signals, and the results show that the modified lidar inversion method is effective and practical in aerosol extinction characteristics’ analysis.
关键词： lidar,Gaussian processing machine learning,ensemble Kalman Filter,signal-to-noise ratio,aerosol extinction characteristics
更新于2025-09-10 09:29:36
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Evaluating VIIRS EPS Aerosol Optical Depth in China: An Intercomparison Against Ground-based Measurements and MODIS
摘要： The Visible Infrared Imaging Radiometer Suite (VIIRS) has been providing routine retrievals of aerosol properties since 2011. As a new generation advanced sensor, VIIRS has certain advantages in terms of spectral and accuracy and spatial resolution, especially with updated algorithm for the NOAA Enterprise Processing System (EPS) since July 2017. However, the VIIRS EPS aerosol products have not been extensively validated. In this study, we evaluate the VIIRS EPS AOD product over mainland China, which has been suffering from heavy aerosol pollution in the recent decade. By comparing collocated VIIRS and ground observations over 12 sites for the Aerosol Robotic Network (AERONET) and 5 sites from the Sun-sky radiometer Observation NETwork (SONET), we find that VIIRS AOD achieves overall reasonable agreement, with 50.61% falling within the expected accuracy interval and a correlation of 0.91 with ground observation. A positive bias of 0.13 is noticed with relatively larger mean bias found in the spring and summer. VIIRS AOD also has a high bias compared with MODIS. The bias is found to be slightly increasing with AOD level. The seasonal variability of VIIRS AOD are also mostly consistent with surface observation and MODIS. VIIRS aerosol model still needs improvement, especially for dust and urban aerosols. A Combined Principal Component Analysis (CPCA) to extract dominant spatial and temporal variability between VIIRS and MODIS data also shows very good agreement, an indication that VIIRS is capable of capturing the major aerosol variability over China.
关键词： MODIS,AERONET,SONET,Aerosol Optical Depth,VIIRS,China
更新于2025-09-10 09:29:36
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Non-Fullerene Based Printed Organic Photodiodes with High Responsivity and MHz Detection Speed
摘要： Digitally printed organic photodiodes (OPDs) are of great interest for the cost-efficient additive manufacturing of single and multi-device detection systems with full freedom of design. Recently reported high-performance non-fullerene acceptors (NFAs) can address the crucial demands of future applications in terms of high operational speed, tunable spectral response as well as device stability. Here, we present the first demonstration of inkjet and aerosol-jet printed OPDs based on the high-performance NFA, IDTBR, in combination with poly(3-hexylthiophene) (P3HT) exhibiting a spectral response up to the NIR. These digitally printed devices reach record responsivities up to 300 mA/W in the visible and NIR spectrum competing with current commercially available technologies based on Si. Furthermore, their fast dynamic response with cut-off frequencies surpassing 2 MHz outperforms most of the state-of the-art organic photodiodes. The successful process translation from spincoating to printing is highlighted by the marginal loss in performance compared to the reference devices, which reach responsivities of 400mA/W and detection speeds of more than 4 MHz. The achieved high device performance and the industrial relevance of the developed fabrication process provide NFAs with an enormous potential for the development of printed photodetection systems.
关键词： aerosol-jet printing,spectral responsivity,non-fullerene acceptor,inkjet printing,digital printing,organic photodiode
更新于2025-09-10 09:29:36
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Assessment of Sun photometer Langley calibration at the high-elevation sites Mauna Loa and Iza?a
摘要： The aim of this paper is to analyze the suitability of the high-mountain stations Mauna Loa and Iza?a for Langley plot calibration of Sun photometers. Thus the aerosol optical depth (AOD) characteristics and seasonality, as well as the cloudiness, have been investigated in order to provide a robust estimation of the calibration uncertainty as well as the number of days that are suitable for Langley calibrations. The data used for the investigations belong to the AERONET and GAW-PFR networks, which maintain reference Sun photometers at these stations with long measurement records: 22 years at Mauna Loa and 15 years at Iza?a. In terms of clear-sky and stable aerosol conditions, Mauna Loa (3397 m a.s.l.) exhibits on average 377 Langley plots (243 morning and 134 afternoon) per year suitable for Langley plot calibration, whereas Iza?a (2373 m a.s.l.) shows 343 Langley plots (187 morning and 155 afternoon) per year. The background AOD (500 nm) values, on days that are favorable for Langley calibrations, are in the range 0.01–0.02 throughout the year, with well-defined seasonality that exhibits a spring maximum at both stations plus a slight summer increase at Iza?a. The statistical analysis of the long-term determination of extraterrestrial signals yields to a calibration uncertainty of ～ 0.25–0.5 %, this uncertainty being smaller in the visible and near-infrared wavelengths and larger in the ultraviolet wavelengths. This is due to atmospheric variability produced by changes in several factors, mainly the AOD. The uncertainty cannot be reduced based only on quality criteria of individual Langley plots and averaging over several days is shown to reduce the uncertainty to the needed levels for reference Sun photometers.
关键词： Sun photometers,aerosol optical depth,Langley calibration,Iza?a,Mauna Loa
更新于2025-09-10 09:29:36
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Monitoring and tracking the trans-Pacific transport of aerosols using multi-satellite aerosol optical depth composites
摘要： The primary goal of this study was to generate a near-real time (NRT) aerosol optical depth (AOD) product capable of providing a comprehensive understanding of the aerosol spatial distribution over the Pacific Ocean, in order to better monitor and track the trans-Pacific transport of aerosols. Therefore, we developed a NRT product that takes advantage of observations from both low-earth orbiting and geostationary satellites. In particular, we utilize AOD products from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Suomi National Polar-orbiting Partnership (NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) satellites. Then, we combine these AOD products with our own retrieval algorithms developed for the NOAA Geostationary Operational Environmental Satellite (GOES-15) and Japan Meteorological Agency (JMA) Multi-functional Transport Satellite (MTSAT-2) to generate a NRT daily AOD composite product. We present examples of the daily AOD composite product for a case study of trans-Pacific transport of Asian pollution and dust aerosols in mid-March 2014. Overall, the new product successfully tracks this aerosol plume during its trans-Pacific transport to the west coast of North America as the frequent geostationary observations lead to a greater coverage of cloud-free AOD retrievals equatorward of about 35° N, while the polar-orbiting satellites provide a greater coverage of AOD poleward of 35° N. However, we note several areas across the domain of interest from Asia to North America where the GOES-15 and MTSAT-2 retrieval algorithms can introduce significant uncertainties into the new product.
关键词： trans-Pacific transport,MODIS,VIIRS,near-real time,aerosol optical depth,MTSAT-2,satellite observations,GOES-15
更新于2025-09-10 09:29:36
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Exploring the applicability and limitations of selected optical scattering instruments for PM mass measurement
摘要： Two optical scattering instruments for particle mass measurement, the Thermo Personal Data RAM (PDR-1500) and the TSI Environmental DustTrak DRX (Model 8543) were evaluated by (1) using poly- and mono-disperse test aerosol in the laboratory, and (2) sampling ambient aerosol. The responses of these optical scattering instruments to different particle characteristics (size, composition, concentration) were compared with responses from reference instruments. A Mie scattering calculation was used to explain the dependence of the optical instruments’ response to aerosol size and composition. Concurrently, the detection efficiency of one Alphasense Optical Particle Counter (OPC-N2) was evaluated in the laboratory as well. The relationship between aerosol mass concentration and optical scattering was determined to be strongly dependent on aerosol size and to a lesser extent on aerosol composition (as reflected in the refractive indices of the materials tested) based on ambient measurements. This confirms that there is no simple way to use optical scattering instruments over a wide range of conditions without adjustments based on knowledge of aerosol size and composition. In particular, a test period measuring ambient aerosol with optical scattering instruments and a mass based method (an Aerodyne Aerosol Mass Spectrometer) determined that roughly two thirds of the variance (R2 = 0.64) of the optical to mass signal ratio is explained by the aerosol mass median diameter alone. These observations and calculations help evaluate the applicability and limitations of these optical scattering instruments, and provide guidance to designing suitable applications for each instrument by considering aerosol sources and aerosol size.
关键词： aerosol composition,optical scattering instruments,aerosol size,PM mass measurement,Mie scattering calculation
更新于2025-09-09 09:28:46
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GOCI Yonsei Aerosol Retrieval (YAER) algorithm and validation during the DRAGON-NE Asia 2012 campaign
摘要： The Geostationary Ocean Color Imager (GOCI) onboard the Communication, Ocean, and Meteorological Satellite (COMS) is the first multi-channel ocean color imager in geostationary orbit. Hourly GOCI top-of-atmosphere radiance has been available for the retrieval of aerosol optical properties over East Asia since March 2011. This study presents improvements made to the GOCI Yonsei Aerosol Retrieval (YAER) algorithm together with validation results during the Distributed Regional Aerosol Gridded Observation Networks – Northeast Asia 2012 campaign (DRAGON-NE Asia 2012 campaign). The evaluation during the spring season over East Asia is important because of high aerosol concentrations and diverse types of Asian dust and haze. Optical properties of aerosol are retrieved from the GOCI YAER algorithm including aerosol optical depth (AOD) at 550 nm, fine-mode fraction (FMF) at 550 nm, single-scattering albedo (SSA) at 440 nm, ?ngstr?m exponent (AE) between 440 and 860 nm, and aerosol type. The aerosol models are created based on a global analysis of the Aerosol Robotic Networks (AERONET) inversion data, and covers a broad range of size distribution and absorptivity, including nonspherical dust properties. The Cox–Munk ocean bidirectional reflectance distribution function (BRDF) model is used over ocean, and an improved minimum reflectance technique is used over land. Because turbid water is persistent over the Yellow Sea, the land algorithm is used for such cases. The aerosol products are evaluated against AERONET observations and MODIS Collection 6 aerosol products retrieved from Dark Target (DT) and Deep Blue (DB) algorithms during the DRAGON-NE Asia 2012 campaign conducted from March to May 2012. Comparison of AOD from GOCI and AERONET resulted in a Pearson correlation coefficient of 0.881 and a linear regression equation with GOCI AOD = 1.083 × AERONET AOD ? 0.042. The correlation between GOCI and MODIS AODs is higher over ocean than land. GOCI AOD shows better agreement with MODIS DB than MODIS DT. The other GOCI YAER products (AE, FMF, and SSA) show lower correlation with AERONET than AOD, but still show some skills for qualitative use.
关键词： retrieval,AE,validation,YAER,SSA,FMF,AOD,DRAGON-NE Asia 2012,aerosol,GOCI
更新于2025-09-09 09:28:46
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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 - Mathematical Tool for a Closure Study of Aerosol Microphysical Property Retrieval Using Lidar and Photometer Data
摘要： We present a project combining lidar, photometer and particle counter data with a regularization software tool for a closure study of aerosol microphysical property retrieval. In a first step only lidar data are used to retrieve the particle size distribution (PSD). Secondly, photometer data are added, which results in a good consistency of the retrieved PSDs. Finally, those retrieved PSDs may be compared with the measured PSD from a particle counter. The data here were taken in Ny Alesund, Svalbard, as an example.
关键词： Raman lidar,regularization,particle microphysics,inversion,photometer,Aerosol
更新于2025-09-09 09:28:46
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30-year lidar observations of the stratospheric aerosol layer state over Tomsk (Western Siberia, Russia)
摘要： There are only four lidar stations in the world, which have almost continuously performed observations of the stratospheric aerosol layer (SAL) state for over the last 30 years. The longest time series of the SAL lidar measurements have been accumulated at the Mauna Loa Observatory (Hawaii) since 1973, the NASA Langley Research Center (Hampton, Virginia) since 1974, and Garmisch-Partenkirchen (Germany) since 1976. The fourth lidar station we present started to perform routine observations of the SAL parameters in Tomsk (56.48° N, 85.05° E, Western Siberia, Russia) in 1986. In this paper, we mainly focus on and discuss the stratospheric background period from 2000 to 2005 and the causes of the SAL perturbations over Tomsk in the 2006–2015 period. During the last decade, volcanic aerosol plumes from tropical Mt. Manam, Soufriere Hills, Rabaul, Merapi, Nabro, and Kelut, and extratropical (northern) Mt. Okmok, Kasatochi, Redoubt, Sarychev Peak, Eyjafjallaj?kull, and Grimsv?tn were detected in the stratosphere over Tomsk. When it was possible, we used the NOAA HYSPLIT trajectory model to assign aerosol layers observed over Tomsk to the corresponding volcanic eruptions. The trajectory analysis highlighted some surprising results. For example, in cases of the Okmok, Kasatochi, and Eyjafjallaj?kull eruptions, the HYSPLIT air-mass backward trajectories, started from altitudes of aerosol layers detected over Tomsk with a lidar, passed over these volcanoes on their eruption days at altitudes higher than the maximum plume altitudes given by the Smithsonian Institution Global Volcanism Program. An explanation of these facts is suggested. The role of both tropical and northern volcanoes eruptions in volcanogenic aerosol loading of the mid-latitude stratosphere is also discussed. In addition to volcanoes, we considered other possible causes of the SAL perturbations over Tomsk, i.e. the polar stratospheric cloud (PSC) events and smoke plumes from strong forest fires. At least two PSC events were detected in 1995 and 2007. We also make an assumption that both the Kelut volcano plume (Indonesia, February 2014) and smoke plumes from massive forest fires occurred in Canada (137 fires in the Northwest Territories, July 2014) and the USA (the Happy Camp Complex fire in California, August–October 2014), with equal probability, could be the cause of the SAL perturbations over Tomsk during the first quarter of 2015.
关键词： volcanic eruptions,polar stratospheric clouds,forest fires,stratospheric aerosol layer,lidar observations
更新于2025-09-09 09:28:46
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Aerosol optical depth in the European Brewer Network
摘要： The high spatial and temporal variability of aerosols makes networks capable of measuring their properties in near real time of high scientific interest. In this work we present and discuss results of an aerosol optical depth algorithm to be used in the European Brewer Network, which provides data in near real time of more than 30 spectrophotometers located from Tamanrasset (Algeria) to Kangerlussuaq (Greenland). Using data from the Brewer Intercomparison Campaigns in the years 2013 and 2015, and the period in between, plus comparisons with Cimel sunphotometers and UVPFR instruments, we check the precision, stability, and uncertainty of the Brewer AOD in the ultraviolet range from 300 to 320 nm. Our results show a precision better than 0.01, an uncertainty of less than 0.05, and a stability similar to that of the ozone measurements for well-maintained instruments. We also discuss future improvements to our algorithm with respect to the input data, their processing, and the characterization of the Brewer instruments for the measurement of aerosols.
关键词： European Brewer Network,uncertainty,ultraviolet range,precision,aerosol optical depth,stability,Brewer spectrophotometer
更新于2025-09-09 09:28:46