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A Geographically and Temporally Weighted Regression Model for Ground-Level PM2.5 Estimation from Satellite-Derived 500 m Resolution AOD
摘要： Regional haze episodes have occurred frequently in eastern China over the past decades. As a critical indicator to evaluate air quality, the mass concentration of ambient fine particulate matters smaller than 2.5 μm in aerodynamic diameter (PM2.5) is involved in many studies. To overcome the limitations of ground measurements on PM2.5 concentration, which is featured in disperse representation and coarse coverage, many statistical models were developed to depict the relationship between ground-level PM2.5 and satellite-derived aerosol optical depth (AOD). However, the current satellite-derived AOD products and statistical models on PM2.5–AOD are insufficient to investigate PM2.5 characteristics at the urban scale, in that spatial resolution is crucial to identify the relationship between PM2.5 and anthropogenic activities. This paper presents a geographically and temporally weighted regression (GTWR) model to generate ground-level PM2.5 concentrations from satellite-derived 500 m AOD. The GTWR model incorporates the SARA (simplified high resolution MODIS aerosol retrieval algorithm) AOD product with meteorological variables, including planetary boundary layer height (PBLH), relative humidity (RH), wind speed (WS), and temperature (TEMP) extracted from WRF (weather research and forecasting) assimilation to depict the spatio-temporal dynamics in the PM2.5–AOD relationship. The estimated ground-level PM2.5 concentration has 500 m resolution at the MODIS satellite's overpass moments twice a day, which can be used for air quality monitoring and haze tracking at the urban and regional scale. To test the performance of the GTWR model, a case study was carried out in a region covering the adjacent parts of Jiangsu, Shandong, Henan, and Anhui provinces in central China. A cross validation was done to evaluate the performance of the GTWR model. Compared with OLS, GWR, and TWR models, the GTWR model obtained the highest value of coefficient of determination (R2) and the lowest values of mean absolute difference (MAD), root mean square error (RMSE), and mean absolute percentage error (MAPE).
关键词： GTWR model,SARA AOD,hourly ground-level PM2.5 concentration,500 m resolution,MODIS,AERONET
更新于2025-09-23 15:23:52
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Evaluating MODIS and MISR aerosol optical depth retrievals over environmentally distinct sites in Pakistan
摘要： The Moderate resolution Imaging SpectroRadiometer (MODIS) and Multi-angle Imaging SpectroRadiometer (MISR) sensors provide aerosol observations suitable for a wide range of applications. The recently released MODIS Collection 6.1 (C061) includes several improvements compared to the previous products which are expected to minimize uncertainties in aerosol retrievals. Such collection needs to be validated and compared with previous collections form the same or other sensors before being applied for further scientific research on a regional scale. This study evaluates the performance of MODIS Collections 6 (C006) and 6.1 (C061) based on two algorithms: Dark Target (DT) and Deep Blue (DB) and the merged product (DTB) onboard the Terra (MOD04) and Aqua (MYD04) satellites, and the MISR AOD retrievals against ground-based Aerosol Robotic Network (AERONET) over two sites (Lahore and Karachi) in Pakistan during 2007–2014. Results elucidated that C061 MODIS AOD exhibited significant improvement as compared to C006, with the 10 km DT (DB) products generally overestimating (underestimating) AOD relative to AERONET AOD. The MOD04 and MYD04-DT and DB (3 and10 km) showed comparable performance over the two sites, whereas The DTB was dominated by DT (DB) pixels over Lahore (Karachi). The MISR showed better performance over Karachi with high reflecting surface than over Lahore with dense vegetation cover. The annual cycle of AOD retrieved by the two sensors were consistent with AERONET AOD, with maximum AOD observed during summer months attributed to prevailing climatic conditions. On seasonal basis, the MODIS algorithms exhibited improved performance over Lahore except during summer where DT and DTB showed relatively low performance, attributed to modulations induced by local meteorology to the prevailing surface conditions. However, the sensors exhibited distinct performance over Karachi, where MODIS-DT (10 km) showed close correspondence with AERONET during autumn and winter, whereas MODIS-DT (3 km) exhibited the converse. The MISR performed relatively well during spring over the two stations. The study gives greater insights on the performance of MODIS and MISR and forms the basis for further research on the validation of satellite derived aerosol products over Pakistan.
关键词： AOD,MISR,MODIS,AERONET
更新于2025-09-23 15:23:52
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Aerosol uncertainty assessment: an integrated approach of remote AQUA MODIS and AERONET data
摘要： The moderate resolution imaging spectroradiometer (MODIS) is one of the widely used sensors to address environmental and climate change subjects with a daily global coverage. MODIS Collection 6 aerosol products at 10-km resolution are used in this study to monitor aerosol variability and assess its uncertainty using ground-based measurements. The aerosol optical depth (AOD) is retrieved by different algorithms based on the pixel surface, determining between land and ocean. Using data collected from Sidi Salem Aerosol Robotic Network (AERONET) station, we computed the accuracy for aerosol optical depth (AOD) retrieved from MODIS aboard the AQUA satellite using two validation methods. The results show a good agreement between MODIS and AERONET data for the study period using both the algorithms. We obtained high values of the correlation coefficient. These findings indicate that MODIS data perform well over Ben Salem AERONET station and are recommended for air quality monitoring over Tunisia. The conducted validation throughout the AERONET leads to a degree of confidence that allows a deep investigation of the AOD spatial variability over Tunisia. Then, MODIS data shows high performance with good certainty to identify the principal dust sources and typical transport paths occurring on the study region.
关键词： AQUA,Remote sensing,AOD,AERONET,Aerosol,MODIS
更新于2025-09-23 15:23:52
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Climatological analysis of the optical properties of aerosols and their direct radiative forcing in the Middle East
摘要： In addition to climate perturbations, various problems such as air pollution, reduction in the visibility and human health hazards were caused by atmospheric aerosols in the Middle East specifically in the last two decades. With the help of the Aerosol Robotic NETwork (AERONET), the measurement of the aerosol optical and radiative properties were carried out over seven sites in the Middle East during 2013. The analysis of the optical properties of aerosols like Single Scattering Albedo (SSA), Angstrom Exponent (AE), Aerosol Optical Depth (AOD), and Asymmetry parameter (ASY) were carried out during the study period. During spring and summer, high values of AOD and low values of AE were found in all sites except CUT-TEPAK (Limassol, Cyprus), which specified the existence of coarse mode particles and dust storms in these seasons. The AE maximum values were found in the summer and fall over CUT-TEPAK and IMS-METU-ERDEMLI(Erdemli, Turkey), whereas in other sites IASBS (Zanjan, Iran), KAUST Campus (Thuwal, Saudi Arabia), Masdar Institute (Masdar, United Arab Emirates), Mezaira (Mezaira, United Arab Emirates) and Solar Village (Riyadh, Saudi Arabia) the peak values of AE occurred in the fall and winter. The maximum values of SSA and ASY were observed in the spring and summer over all sites except over CUT-TEPAK and IMS-METU-ERDEMLI. The Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model has been used for the calculations of the Aerosol Radiative Forcing (ARF) over the selected sites. We obtained negative value of ARF at the surface, which suggesting its cooling effects because of the loss of radiation back to space due to aerosols. The averaged ARF values at the SuRFace (SRF) of the earth were -43.8 Wm-2, -31 Wm-2, -56.8 Wm-2, -61.7 Wm-2, -52.5 Wm-2, -54.9 Wm-2, and -72.2 Wm-2, over CUT-TEPAK, IASABS, IMS-METU-ERDEMLI, KAUST Campus, Masdar Institute, Mezaira and Solar Village, respectively. While the positive value of atmospheric ARF showed heating of the atmosphere.
关键词： Middle East.,Aerosol Optical Depth,SBDART,Aerosol Radiative Forcing,AERONET
更新于2025-09-23 15:23:52
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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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A 10-year record of aerosol optical properties and radiative forcing over three environmentally distinct AERONET sites in Kenya, East Africa
摘要： In the framework of Aerosol Robotic Network (AERONET), the aerosol optical, microphysical and radiative properties were investigated over three sites (CRPSM_Malindi, Nairobi, and ICIPE_Mbita) in Kenya, East Africa (EA) during 2006-2015. The annual mean (±σ) aerosol optical depth at 440 nm (AOD440) was found high at Mbita (0.27±0.09) followed by Malindi (0.26±0.07), and low at Nairobi (0.19±0.04). Whereas, the seasonal mean AOD440 noticed high (low) values during the local dry (wet) seasons. The aerosol optical properties: AOD, single scattering albedo (SSA), asymmetry parameter (ASY), and complex aerosol refractive index (RI) exhibited significant temporal and spectral heterogeneities illustrating the complexity of aerosol types with an abundance of fine-mode aerosols during the local dry (JJA) season. Characterization of major aerosol types revealed the dominance of mixed-type followed by biomass burning aerosols. The aerosol volume size distribution revealed that the coarse- over fine-mode aerosols showed a significant contribution to the total volume particle concentration, especially at high (> 0.3) AOD440. Further, the aerosol columnar number size distribution (CSD) retrieved from the King’s inversion of spectral AOD exhibited a power law distribution affirming multiplicity of aerosol sources. The direct aerosol radiative forcing values simulated in the shortwave region using the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model showed good correlation (r=>0.85) with the AERONET derived ones at the top-of-atmosphere (TOA), bottom-of-atmosphere (BOA) and within the atmosphere (ATM). The annual mean (±σ) TOA, BOA, and ATM forcing values were found in the range from -8.10±3.75 to -13.23±4.87, -34.54±4.86 to -46.11±10.27, and 26.63±6.43 to 36.24±7.26 Wm-2, respectively, with an atmospheric heating rate (AHR) of 0.74±0.12–1.02±0.20 K day-1. The SBDART-derived DARF exhibited significant temporal heterogeneity with high (low) during the local dry (wet) seasons. Results derived from the present study forms a basis for regional climate change studies and could increase the accuracy of climate models over this unexplored region of Africa.
关键词： Aerosol radiative forcing,Aerosol optical depth,Size distribution,East Africa,AERONET,Single scattering albedo
更新于2025-09-23 15:22:29
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Comparison and evaluation of MODIS Multi-angle Implementation of Atmospheric Correction (MAIAC) aerosol product over South Asia
摘要： The Multiangle Implementation of Atmospheric Correction (MAIAC) is a new generic algorithm applied to collection 6 (C6) MODIS measurements to retrieve Aerosol Optical Depth (AOD) over land at high spatial resolution (1 km). This study is the first evaluation of the MAIAC AOD from MODIS Aqua (A) and Terra (T) satellites between 2006 and 2016 over South Asia. The retrieval accuracy of MAIAC was assessed by comparing it to ground-truth AErosol RObotic NETwork (AERONET) AOD, as well as to AOD retrieved by the two operational MODIS algorithms: Dark Target (DT) and Deep Blue (DB). MAIAC AOD showed higher spatial coverage and retrieval frequency than either the DT or the DB AOD retrievals. The high spatial resolution of the MAIAC retrievals enhances the capability to distinguish aerosol sources and to determine fine aerosol features, such as wildfire smoke plumes and haze over complex geographical regions, and provides more retrievals in conditions that are cloudy or when the surface is partially covered by snow. In comparison to AERONET AOD, MAIAC AOD shows a better accuracy than both DT and DB AOD. A higher number of MAIAC-AERONET AOD matchups demonstrate the capability of MAIAC to retrieve AOD over varied surfaces, different aerosol types and loadings. Our results demonstrate high retrieval accuracy in term of the Expected Error (EE) (A/T, EE: 72.22%, 73.50%), and low root mean square error (A/T, RMSE: 0.148, 0.164), root mean bias (RMB) (A/T, RMB: 0.978, 1.049) and mean absolute error (MAE) (A/T, MAE: 0.098, 0.096). Moreover, MAIAC has a lower bias as a function of the viewing geometry and the aerosol type among the three retrieval algorithms. MAIAC performed well over bright and vegetated land surfaces, showing the highest retrieval accuracy over dense vegetation and particularly well in retrieving smoke AOD, yet it underestimated dust AOD. In conclusion, MAIAC's ability to provide AOD at high spatial resolution appears promising over South Asia, thus having advantage over contemporary aerosol retrieval algorithms for epidemiological and climatological studies.
关键词： South Asia,AOD,MODIS,IGP,Aerosols,AERONET,MAIAC
更新于2025-09-19 17:15:36
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Significant decrease of photovoltaic power production by aerosols. The case of Santiago de Chile
摘要： Santiago de Chile frequently suffers from atmospheric pollution that contributes to the decrease of solar irradiance on the surface, leading to losses in the energy output of photovoltaic systems. In this study, a simple model is used to estimate the effect of aerosols on the solar irradiance over the city throughout the year, using as input AERONET sunphotometer data and other in-situ measurements. The results show reductions of 3.5% and 14.1% for global horizontal and direct normal irradiance respectively and an increase of 35.4% for diffuse horizontal irradiance between the actual condition in Santiago and a hypothetical atmosphere free of aerosols. These effects translate approximately to an annual difference in the energy output of -7.2% and -8.7% for monocrystalline and amorphous silicon PV technologies respectively, and an annual difference of -16.4% for a CPV technology, showing that aerosols can have a significant effect on the photovoltaic energy production.
关键词： Solar irradiance,AERONET,Chile,Air pollution,Santiago,Aerosols,Photovoltaics
更新于2025-09-19 17:13:59
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Are EARLINET and AERONET climatologies consistent? The case of Thessaloniki, Greece
摘要： In this study we investigate the climatological behavior of the aerosol optical properties over Thessaloniki during the years 2003-2017. For this purpose, measurements of two independent instruments, a lidar and a sun photometer, were deployed. These two instruments represent two individual networks, the European Lidar Aerosol Network (EARLINET) and the Aerosol Robotic Network (AERONET). They include different measurement schedules. Fourteen years of lidar and sun photometer measurements were analyzed in order to obtain the annual cycles and trends of multiple optical and geometrical aerosol properties in the boundary layer, in the free troposphere and for the whole atmospheric column. The analysis resulted in consistent statistically significant and decreasing AOD355nm trends of -21.0% and -16.6% per decade in the study period over Thessaloniki for the EARLINET and the AERONET datasets respectively. Therefore, the analysis implies that the EARLINET sampling schedule can be quite effective in producing data that can be applied to climatological studies. It has also been confirmed that the observed decreasing trend is mainly attributed to changes in the aerosol properties inside the boundary layer. Seasonal profiles of the most dominant aerosol mixture types have been generated from the lidar data. The higher values of the extinction at 355nm appear in summer, while the lower ones appear in winter. The dust component is much more dominant in the free troposphere than in the boundary layer during summer, while the opposite is observed in winter. The strongest biomass burning episodes tend to occur during summer in the free troposphere and are probably attributed to wildfires rather than agricultural fires that are predominant during spring and autumn. This kind of information can be quite useful for applications that require a priori aerosol profiles. For instance, they can be utilized in models that require aerosol climatological data as input, in the development of algorithms for satellite products, and also in passive remote sensing techniques that require knowledge of the aerosol vertical distribution.
关键词： aerosol optical properties,EARLINET,climatology,AERONET,Thessaloniki
更新于2025-09-10 09:29:36
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Accuracy Analysis of the Aerosol Backscatter Coefficient Profiles Derived from the CYY-2B Ceilometer
摘要： Ceilometers are originally designed for cloud base height monitoring. Since a few years, the number of ceilometers available worldwide is rapidly increasing, and these simple backscatter lidars are investigated to be used for aerosol research. This study presents an assessment of the potential of CYY-2B ceilometer for the quantitative retrieval of aerosol properties. The signal-to-noise ratio of the ceilometer is calculated, and the e?ective height of inversion is determined. It is shown that the e?ective height of the ceilometer for backscatter coe?cient pro?le inversion is 3-4 km at night and about 1.5–2 km during the day, which is lower than that of the micropulse lidar (MPL) system. The accuracy of the backscatter coe?cient pro?les derived from the CYY-2B ceilometer is analyzed by using the Vaisala CL51 ceilometer, MPL, forward scatter visibility instrument, and aerosol optical depth (AOD) dataset from aerosol robotic network (AERONET). Spectral conversions of the ceilometer’s and lidar’s data are performed using the ?Angstr¨om exponent estimated by AERONET measurements. A good agreement is found between two ceilometers and the MPL lidar in backscatter coe?cient pro?les inversion. The AODs agree well with the AERONET AODs during the observation period of small AODs. However, for the period of large AODs, the results are approximately 50%–60% of AERONET AODs. The limited range of extinction integration is the main cause of this problem.
关键词： ceilometer,AERONET,aerosol optical depth,aerosol backscatter coefficient,signal-to-noise ratio
更新于2025-09-10 09:29:36