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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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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Near Real-Time Modis-Detected Flood Monitoring Coupling with Composite White-Object Index
摘要： Floods is the greatest natural disasters that affect human society than any other type of natural disaster. With the availability of satellite rainfall analyses at fine time and space resolution, it has also become possible to mitigate such hazards on a near-global basis. In this research, we construct a real-time flood monitoring system using White Object Index (WOI) composite. The efficiency of the WOI was tested by comparing the MVC and MOD35.
关键词： White Object Index,Mekong river MLSWI,MODIS,flood
更新于2025-09-23 15:23:52
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Dust Detection and Aerosol Properties Over Arabian Sea Using MODIS Data
摘要： The present study deals with the use of Moderate Resolution Imaging Spectroradiometer (MODIS) thermal infrared bands in the dust detection. Eight dust storm cases over the Arabian Sea have been selected (four TERRA and four AQUA) during the year 2002–2008. The brightness temperature (BT) difference method has been applied on MODIS thermal bands 29 (8 μm), 31 (11 μm) and 32 (12 μm) to detect dust storms over the Arabian Sea. The performance assessment of BT differences (BT29–BT31 and BT31–BT32) has shown that BT31–BT32 has performed better to BT29–BT31. We suggest that BT31–BT32 is an effective combination of MODIS bands for dust detection over oceans and sea. The maximum (Dmax) and minimum dust (Dmin) intensity locations have also been identified in all the eight dust storm cases. The aerosol properties (aerosol optical thickness, τ; asymmetry factor g and Angstrom exponent α) over Dmax and Dmin have been studied using MODIS Level 2 data. In AQUA dust storms cases τ values (Dmax) were higher than TERRA dust cases, whereas g values were nearly same. The α was always positive in case of TERRA dust cases; however in AQUA negative α was also reported. Afternoon dust storms are more intense compared to forenoon dust storms and dust particles are also coarser.
关键词： BT difference,Arabian Sea,Dust detection,MODIS,Dust aerosol properties
更新于2025-09-23 15:23:52
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An improved algorithm for retrieving the fine-mode fraction of aerosol optical thickness. Part 2: Application and validation in Asia
摘要： Since small aerosol particles are mostly anthropogenic, the fine-mode aerosol optical thickness (fAOT) can be used to infer PM2.5 amounts. However, satellite-based fAOT products such as those from the Moderate Resolution Imaging Spectroradiometer (MODIS) are highly uncertain over land. An improved fAOT retrieval method called the look-up table–spectral deconvolution algorithm (LUT-SDA) was tested and improved using data from Asia. The improvement is achieved by accounting for seasonal changes instead of using constant annual mean values of the aerosol parameters used in the LUT-SDA derived from the Aerosol Robotic Network (AERONET) data from 2010 to 2014. Compared with the previous version of the LUT-SDA developed for Beijing, Hong Kong, and Osaka, the updated LUT-SDA generates more accurate fine-mode fractions (FMFs) with the total mean root-mean-square error (RMSE) decreasing from 0.24 to 0.18. The updated LUT-SDA was then applied to retrieve fAOT and was validated by retrievals from 45 AERONET sites over the period 2015 to 2016. A good accuracy was achieved by this method with 31% of the validation sites having > 50% of retrievals falling within the estimated error (EE) envelope ± (0.05 + 0.15 × AERONET fAOT) and 42% of the validation sites having 40–50% of retrievals falling within the EE envelope. In the total validation and comparison with the MODIS Collection 6 fAOT, the fAOT retrievals from the LUT-SDA agreed more closely with AERONET retrievals, showing a low bias. About 48% of the LUT-SDA-based fAOT retrievals fell within the EE envelope (RMSE = 0.29), while ~22% of the MODIS-based fAOT retrievals fell within the EE envelope (RMSE = 0.42). The fAOT was significantly underestimated by the MODIS algorithm in most areas of Asia with many values of zero. This study demonstrates that the refined LUT-SDA method is valid for the large-scale estimation of fAOT from satellite images.
关键词： MODIS,Aerosol optical thickness,Fine-mode fraction
更新于2025-09-23 15:23:52
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Assessment of Satellite Aerosol Optical Depth to Estimate Particulate Matter Distribution in Valencia City
摘要： The estimation of exposure to PM10 and PM2.5 requires the knowledge of surface concentration at high temporal and spatial resolutions. In this paper, the relation between PM10 and PM2.5 ground data and MODIS AOD satellite data has been evaluated to determine the concentration of particulate matter in Valencia, Spain. This was done using data from the Valencian Network of Surveillance and Control of Air Pollution and the scientific data set "Optical Depth Land and Ocean" from MODIS Terra and Aqua with 3km of spatial resolution. The linear regression model for PM10 provided a regression slope of 25.99 μg.m-3 and an interception of 12.07 μg.m-3 (RMSE = 8.61 μg.m-3), while for PM2.5 the slope and interception were 26.87 μg.m-3 and 5.98 μg.m-3 (RMSE = 5.5 μg.m-3).
关键词： Valencia,particulate matter,air quality,AOD,MODIS
更新于2025-09-23 15:22:29
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Validation of MODIS-Aqua bio-optical algorithms for phytoplankton absorption coefficient measurement in optically complex waters of El Rincón (Argentina)
摘要： El Rincón is a highly productive area in the inner-shelf of the Argentine Sea, southern Buenos Aires Province (39°S–62.5°W; 41.5°S–60°W), regarded as the habitat for commercially valuable ?sh species and important for local artisanal ?sheries. The aims of this work were to characterize for the ?rst time the in situ absorption coe?cient of phytoplankton (aph(λ)) in relation to phytoplankton composition and chlorophyll-a (Chl-a) concentration, and to evaluate the satellite retrieval of aph(443) using two atmospheric correction algorithms and three bio-optical semi-analytical algorithms in order to de?ne which is more suitable for the study area. A total of 28 oceanographic cruises were performed between November 2013 and March 2017 and the sampling included physical variables (temperature, salinity, suspended particulate matter, SPM), Chl-a, phytoplankton absorption and composition. The phytoplankton community was mainly dominated by chain-forming diatoms from the microplankton size class (40–80%), while a single coccolithophore, Gephyrocapsa oceanica (cell diameter < 10 μm) was a key component (up to 40%) of the nanoplankon. In situ Chl-a (mean 1.8 mg m?3) and aph(443) (mean 0.052 m?1) generally covariated with no clear seasonality. Their correlation was rather low (R2 = 0.52) and with high scattering, in agreement with the high interannual variability of phytoplankton composition. Further, the relative low mean speci?c absorption coe?cient of phytoplankton (aph*(443), 0.032 m2 (mg Chl-a)?1) and (aph*(676), 0.014 m2 (mg Chl-a)?1) denoted the presence of big cells and pigment packaging e?ect. Aside from the optical complexity of these waters, reasonable results were found using the Quasi Analytical Algorithm in retrieving aph coe?cient (R2 = 0.55, Bias = 19%) and switching the atmospheric correction algorithm depending on the distance to the coast, the depth and turbidity. The results found in this paper present for the ?rst time the phytoplankton composition and absorption of algal material characteristics and the derived implication on the performance of bio-optical algorithms in the optically complex waters of El Rincon.
关键词： Absorption by phytoplankton,Bio-optical algorithms,Turbid coastal waters,Phytoplankton composition,Validation,MODIS-Aqua
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 (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Retrieval and Validation of Sea Ice Concentration from AMSR-E/AMSR2 in Polar Regions
摘要： Sea ice concentration (SIC) is an important sea ice parameter of the atmosphere-ice-ocean system in the polar region. Daily 6.25 km AMSR-E/AMSR2 SIC from Bremen University (UB) is one of the widely used SIC products. In this paper, MODIS data and aerial image are used to validate this product. The results show that the daily mean AMSR-E ASI products underestimate SICs about 17.9% based on the aerial image, and underestimate SICs about8.5% based on MODIS image. The sea ice extent (SIE) and sea ice area (SIA) which are derived from SIC by ASI algorithm, Dynamic Tie-point ASI algorithm (DT-ASI) as well as NT algorithm are compared.
关键词： Retrieval,Validation,aerial image,Sea ice concentration,AMSR-E,MODIS
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 - The Difference of Rrs Product Derived From Modis Meris and Seawifs in South China Sea
摘要： This study presents the difference of normalized remote sensing reflectance (Rrs) between SeaWiFS, MERIS and MODIS with in situ data in the SCS. The results show that all the satellite-derived Rrs are less than the in situ data, and the APD(Absolute Percentage Difference) of the Rrs from the three satellite sensors are mostly less than 20%, except band 412 and 660 nm in global ocean and band 555and 660nm in SCS. The blue band of the three missions have the good performances, whose APD are less than 15%. The performances of MODIS Rrs is better than MERIS (or SeaWiFS). And, compared with each other in the SCS , the results show that the Rrs of the three missions are generally agree well with each other, but they still have big differences in the coastal area. The MODIS Rrs is bigger than MERIS’s and SeaWiFS’s in the 412, 443 and 488 nm band. The differences between MERIS (or SeaWiFS) and MODIS change with band (488 nm is the best one). And the differences among three missions for blue band has seasonal variation in the SCS from 2008 to 2010.
关键词： Validation,SCS,cross validation,MODIS/MERIS/SeaWiFS,Rrs
更新于2025-09-23 15:21:21