How Long Is Too Long? Variogram Analysis of AERONET Data to Aid Aerosol Validation and Intercomparison Studies

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dc.contributor.authorSayer, Andrew
dc.date.accessioned2022-10-26T16:51:13Z
dc.date.available2022-10-26T16:51:13Z
dc.date.issued2020-09-14
dc.description.abstractGeophysical data sets derived from satellite sensors, ground/airborne instrumentation, andcomputational models are often compared against each other. A common example is the validation ofsatellite aerosol optical depth (AOD) retrievals against measurements from Aerosol Robotic Network(AERONET) Sun photometers. Spatiotemporal mismatch between data set sampling means that uncapturedvariation in the underlying geophysicalfield introduces apparent disagreement into such comparisons,known as representation or collocation matchup uncertainty. This study uses variogram analysis ofAERONET data to estimate temporal mismatch uncertainties and decorrelation time scales for the globalAERONET record. As well as total AOD, thefine‐and coarse‐mode AODs, Ångström Exponent (AE), andfine‐mode fraction (FMF) of AOD are analyzed. Globally, a time difference of 30 min typically induces from0.011–0.035 variation in AOD. For total,fine, and coarse AODs the typical time to decorrelation is around2–10 days. For AE and FMF it is 3–33 days; that is, aerosol systems often persist significantly longer thanindividual events in them. Biomass burning regions tend to show the largest and fastest subdaily AODvariability and also longest times to decorrelation. Some sites show significant season‐to‐season variations inbehavior. These results can be used to inform site‐specific time collocation thresholds for aerosol validationanalyses and account for temporal variation when estimating data set uncertainty. They also haveimplications for comparisons between different satellite products or models, data aggregation, and timeseries analyses. Results are provided on a site‐by‐site basis to facilitate use by other researchers.en_US
dc.description.sponsorshipThis research was funded by the NASA PACE project. The AERONET team and site PIs are thanked for the creation and stewardship of the Sun photometer data and satellite retrieval teams and data centers for the satellite products used. This manuscript was prepared using the Overleaf online Editor (https://overleaf.com). The author is grateful to Prof. Noel Cressie (University of Wollongong, Australia) for useful discussions and suggested reading and Dr. P. Jeremy Werdell (NASA GSFC) for comments and questions on a draft of this work. The author thanks one anonymous referee for his/her helpful review of this manuscript. Zenodo is thanked for hosting the data.en_US
dc.description.urihttps://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020EA001290en_US
dc.format.extent19 pagesen_US
dc.genrejournal articlesen_US
dc.identifierdoi:10.13016/m2if3h-unok
dc.identifier.citationSayer, A. M. (2020). How long is too long? Variogram analysis of AERONET data to aid aerosol validation and intercomparison studies. Earth and Space Science, 7, e2020EA001290. https://doi.org/10.1029/2020EA001290en_US
dc.identifier.urihttps://doi.org/10.1029/2020EA001290
dc.identifier.urihttp://hdl.handle.net/11603/26237
dc.language.isoen_USen_US
dc.publisherAGUen_US
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC GESTAR II Collection
dc.rightsAttribution 4.0 International (CC BY 4.0)*
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/*
dc.titleHow Long Is Too Long? Variogram Analysis of AERONET Data to Aid Aerosol Validation and Intercomparison Studiesen_US
dc.typeTexten_US
dcterms.creatorhttps://orcid.org/0000-0001-9149-1789en_US

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