{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T04:15:47Z","timestamp":1760242547873,"version":"build-2065373602"},"reference-count":38,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2017,11,16]],"date-time":"2017-11-16T00:00:00Z","timestamp":1510790400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Moderate resolution imaging spectroradiometer (MODIS) aerosol optical depth (AOD) products have been widely used to characterize the temporal variations and spatial distributions of atmospheric aerosols. In the present study, we evaluate the performance of four Terra and Aqua MODIS Collection 6 (C6) quality assured AOD products in the Pearl River Delta (PRD) region, a humid subtropical region. The 10 km AOD products retrieved by the Dark Target (DT) and Deep Blue (DB) algorithms, the merged DT\/DB (DTDB) 10 km product, and the DT 3 km AOD product were obtained for 2006\u20132015. These products were compared with Aerosol Robotic Network (AERONET) observations, and with each other. The Terra- and Aqua-derived AODs are quantitatively similar. However, there are significant differences among the four AOD products. The DT 10 km product correlates more closely with AERONET AOD observations than does the DB 10 km product. The latter tends to underestimate the AOD, whereas the former typically overestimates it for highly urbanized areas. The DTDB 10 km product is mainly derived from the DT 10 km product; it does not provide a gap-filled data set, because valid DB 10 km retrievals are not included in the merged product even when DT 10 km retrievals are unavailable. Therefore, the DT\/DB merging protocol should be improved. The DT 3 km AOD product closely mimics the DT 10 km product; however, it contains fewer data than the DT 10 km product over water-contaminated areas. In addition, although the quality assured AOD products are recommended for use in quantitative applications by the MODIS aerosol science team, the sampling frequency of these products is generally lower than 25%. Thus, the sampling issues of these products should be considered in humid subtropical areas.<\/jats:p>","DOI":"10.3390\/rs9111173","type":"journal-article","created":{"date-parts":[[2017,11,16]],"date-time":"2017-11-16T11:10:02Z","timestamp":1510830602000},"page":"1173","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":9,"title":["An Evaluation of Four MODIS Collection 6 Aerosol Products in a Humid Subtropical Region"],"prefix":"10.3390","volume":"9","author":[{"given":"Ming","family":"Zhang","sequence":"first","affiliation":[{"name":"School of Resources and Environmental Engineering, Wuhan University of Technology, Wuhan 430070, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bo","family":"Huang","sequence":"additional","affiliation":[{"name":"Department of Geography and Resource Management, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Qingqing","family":"He","sequence":"additional","affiliation":[{"name":"Department of Geography and Resource Management, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2017,11,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"215","DOI":"10.1038\/nature01091","article-title":"A satellite view of aerosols in the climate system","volume":"419","author":"Kaufman","year":"2002","journal-title":"Nature"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"709","DOI":"10.1080\/10473289.2006.10464485","article-title":"Health effects of fine particulate air pollution: Lines that connect","volume":"56","author":"Pope","year":"2006","journal-title":"J. Air Waste Manag. Assoc."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"2755","DOI":"10.5194\/angeo-27-2755-2009","article-title":"Uncertainties in satellite remote sensing of aerosols and impact on monitoring its long-term trend: A review and perspective","volume":"27","author":"Li","year":"2009","journal-title":"Ann. Geophys."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"95","DOI":"10.1016\/j.earscirev.2012.10.008","article-title":"Remote sensing of atmospheric aerosol using spaceborne optical observations","volume":"116","author":"Kokhanovsky","year":"2013","journal-title":"Earth-Sci. Rev."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"17051","DOI":"10.1029\/96JD03988","article-title":"Operational remote sensing of tropospheric aerosol over land from eos moderate resolution imaging spectroradiometer","volume":"102","author":"Kaufman","year":"1997","journal-title":"J. Geophys. Res. Atmos."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"9296","DOI":"10.1002\/jgrd.50712","article-title":"Enhanced deep blue aerosol retrieval algorithm: The second generation","volume":"118","author":"Hsu","year":"2013","journal-title":"J. Geophys. Res. Atmos."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"2989","DOI":"10.5194\/amt-6-2989-2013","article-title":"The collection 6 modis aerosol products over land and ocean","volume":"6","author":"Levy","year":"2013","journal-title":"Atmos. Meas. Tech."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.rse.2014.08.008","article-title":"A satellite-based geographically weighted regression model for regional pm2.5 estimation over the Pearl River delta region in china","volume":"154","author":"Song","year":"2014","journal-title":"Remote Sens. Environ."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"156","DOI":"10.1016\/j.atmosenv.2016.03.040","article-title":"Satellite-derived high resolution pm2.5 concentrations in yangtze river delta region of china using improved linear mixed effects model","volume":"133","author":"Ma","year":"2016","journal-title":"Atmos. Environ."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"267","DOI":"10.1029\/2003GL018174","article-title":"Intercomparison between satellite-derived aerosol optical thickness and pm2.5 mass: Implications for air quality studies","volume":"30","author":"Wang","year":"2003","journal-title":"Geophys. Res. Lett."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"847","DOI":"10.1289\/ehp.0901623","article-title":"Global estimates of ambient fine particulate matter concentrations from satellite-based aerosol optical depth: Development and application","volume":"118","author":"Martin","year":"2010","journal-title":"Environ. Health Perspect."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"645","DOI":"10.3155\/1047-3289.59.6.645","article-title":"Remote sensing of particulate pollution from space: Have we reached the promised land?","volume":"59","author":"Hoff","year":"2009","journal-title":"J. Air Waste Manag. Assoc."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"947","DOI":"10.1175\/JAS3385.1","article-title":"The modis aerosol algorithm, products, and validation","volume":"62","author":"Remer","year":"2005","journal-title":"J. Atmos. Sci."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"10399","DOI":"10.5194\/acp-10-10399-2010","article-title":"Global evaluation of the collection 5 modis dark-target aerosol products over land","volume":"10","author":"Levy","year":"2010","journal-title":"Atmos. Chem. Phys."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"6992","DOI":"10.1002\/2015JD023360","article-title":"Comparison and evaluation of the modis collection 6 aerosol data in china","volume":"120","author":"Tao","year":"2015","journal-title":"J. Geophys. Res. Atmos."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"1255","DOI":"10.5194\/acp-16-1255-2016","article-title":"Evaluation of viirs, goci, and modis collection 6\u202faod retrievals against ground sunphotometer observations over east asia","volume":"16","author":"Xiao","year":"2016","journal-title":"Atmos. Chem. Phys."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"7864","DOI":"10.1002\/jgrd.50600","article-title":"Validation and uncertainty estimates for modis collection 6 \u201cdeep blue\u201d aerosol data","volume":"118","author":"Sayer","year":"2013","journal-title":"J. Geophys. Res. Atmos."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"13965","DOI":"10.1002\/2014JD022453","article-title":"Modis collection 6 aerosol products: Comparison between aqua\u2019s e-deep blue, dark target, and \u201cmerged\u201d data sets, and usage recommendations","volume":"119","author":"Sayer","year":"2014","journal-title":"J. Geophys. Res. Atmos."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"7941","DOI":"10.1002\/2015JD023082","article-title":"Evaluation of modis aerosol retrieval algorithms over the beijing-tianjin-hebei region during low to very high pollution events","volume":"120","author":"Bilal","year":"2015","journal-title":"J. Geophys. Res. Atmos."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"1065","DOI":"10.5194\/acp-16-1065-2016","article-title":"The importance of temporal collocation for the evaluation of aerosol models with observations","volume":"16","author":"Schutgens","year":"2016","journal-title":"Atmos. Chem. Phys."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"6157","DOI":"10.1016\/j.atmosenv.2008.03.025","article-title":"Regional integrated experiments on air quality over pearl river delta 2004 (pride-prd2004): Overview","volume":"42","author":"Zhang","year":"2008","journal-title":"Atmos. Environ."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"683","DOI":"10.1016\/S1352-2310(00)00335-6","article-title":"Internal boundary layer structure under sea-breeze conditions in Hong Kong","volume":"35","author":"Liu","year":"2001","journal-title":"Atmos. Environ."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"11670","DOI":"10.1021\/acs.est.5b02776","article-title":"Assessing long-term trend of particulate matter pollution in the pearl river delta region using satellite remote sensing","volume":"49","author":"Li","year":"2015","journal-title":"Environ. Sci. Technol."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1424","DOI":"10.1016\/j.atmosenv.2007.11.025","article-title":"Long-term trend of visibility and its characterizations in the pearl river delta (prd) region, china","volume":"42","author":"Deng","year":"2008","journal-title":"Atmos. Environ."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"216","DOI":"10.1016\/j.atmosres.2014.02.011","article-title":"Observation of aerosol optical properties and particulate pollution at background station in the pearl river delta region","volume":"143","author":"Chen","year":"2014","journal-title":"Atmos. Res."},{"key":"ref_26","first-page":"1","article-title":"Second-generation operational algorithm: Retrieval of aerosol properties over land from inversion of moderate resolution imaging spectroradiometer spectral reflectance","volume":"112","author":"Levy","year":"2007","journal-title":"J. Geophys. Res. Atmos."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"557","DOI":"10.1109\/TGRS.2004.824067","article-title":"Aerosol properties over bright-reflecting source regions","volume":"42","author":"Hsu","year":"2004","journal-title":"IEEE Trans. Geosci. Remote Sens."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"12,157","DOI":"10.1002\/2015JD023878","article-title":"Effect of modis terra radiometric calibration improvements on collection 6 deep blue aerosol products: Validation and terra\/aqua consistency","volume":"120","author":"Sayer","year":"2015","journal-title":"J. Geophys. Res. Atmos."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1747","DOI":"10.5194\/amt-6-1747-2013","article-title":"Modis 3 km aerosol product: Applications over land in an urban\/suburban region","volume":"6","author":"Munchak","year":"2013","journal-title":"Atmos. Meas. Tech."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"1829","DOI":"10.5194\/amt-6-1829-2013","article-title":"Modis 3 km aerosol product: Algorithm and global perspective","volume":"6","author":"Remer","year":"2013","journal-title":"Atmos. Meas. Tech."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/S0034-4257(98)00031-5","article-title":"Aeronet\u2014A federated instrument network and data archive for aerosol characterization","volume":"66","author":"Holben","year":"1998","journal-title":"Remote Sens. Environ."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1029\/2001GL013206","article-title":"A spatio-temporal approach for global validation and analysis of modis aerosol products","volume":"29","author":"Ichoku","year":"2002","journal-title":"Geophys. Res. Lett."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"31333","DOI":"10.1029\/1999JD900923","article-title":"Wavelength dependence of the optical depth of biomass burning, urban, and desert dust aerosols","volume":"104","author":"Eck","year":"1999","journal-title":"J. Geophys. Res. Atmos."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"370","DOI":"10.1080\/2150704X.2015.1035771","article-title":"Using satellite data to estimate particulate air quality in a subtropical city: An evaluation of accuracy and sampling issues","volume":"6","author":"Zhang","year":"2015","journal-title":"Remote Sens. Lett."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"5237","DOI":"10.5194\/amt-8-5237-2015","article-title":"Adaption of the modis aerosol retrieval algorithm using airborne spectral surface reflectance measurements over urban areas: A case study","volume":"8","author":"Mey","year":"2015","journal-title":"Atmos. Meas. Tech."},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Nichol, J., and Bilal, M. (2016). Validation of modis 3 km resolution aerosol optical depth retrievals over Asia. Remote Sens., 8.","DOI":"10.3390\/rs8040328"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"1004","DOI":"10.1080\/01621459.2012.694717","article-title":"Spatial statistical data fusion for remote sensing applications","volume":"107","author":"Nguyen","year":"2012","journal-title":"J. Am. Stat. Assoc."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"4034","DOI":"10.1002\/2015JD024571","article-title":"Spatiotemporal fusion of multiple-satellite aerosol optical depth (aod) products using bayesian maximum entropy method","volume":"121","author":"Tang","year":"2016","journal-title":"J. Geophys. Res. Atmos."}],"container-title":["Remote Sensing"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2072-4292\/9\/11\/1173\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T18:49:46Z","timestamp":1760208586000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2072-4292\/9\/11\/1173"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2017,11,16]]},"references-count":38,"journal-issue":{"issue":"11","published-online":{"date-parts":[[2017,11]]}},"alternative-id":["rs9111173"],"URL":"https:\/\/doi.org\/10.3390\/rs9111173","relation":{},"ISSN":["2072-4292"],"issn-type":[{"type":"electronic","value":"2072-4292"}],"subject":[],"published":{"date-parts":[[2017,11,16]]}}}