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A review and framework for the evaluation of pixel-level uncertainty estimates in satellite aerosol remote sensing

Sayer, A.M. and Govaerts, Yves and Kolmonen, Pekka and Lipponen, Antti and Luffarelli, Marta and Mielonen, Tero and Patadia, Falguni and Popp, Thomas and Povey, Adam and Stebel, Kerstin and Witek, Marcin l. (2020) A review and framework for the evaluation of pixel-level uncertainty estimates in satellite aerosol remote sensing. Atmospheric Measurement Techniques (AMT), 13, pp. 373-404. Copernicus Publications. doi: 10.5194/amt-13-373-2020. ISSN 1867-1381.

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Official URL: https://www.atmos-meas-tech.net/13/373/2020/

Abstract

Recent years have seen the increasing inclusion of per-retrieval prognostic (predictive) uncertainty estimates within satellite aerosol optical depth (AOD) data sets, providing users with quantitative tools to assist in the optimal use of these data. Prognostic estimates contrast with diagnostic (i.e. relative to some external truth) ones, which are typically obtained using sensitivity and/or validation analyses. Up to now, however, the quality of these uncertainty estimates has not been routinely assessed. This study presents a review of existing prognostic and diagnostic approaches for quantifying uncertainty in satellite AOD retrievals, and it presents a general framework to evaluate them based on the expected statistical properties of ensembles of estimated uncertainties and actual retrieval errors. It is hoped that this framework will be adopted as a complement to existing AOD validation exercises; it is not restricted to AOD and can in principle be applied to other quantities for which a reference validation data set is available. This framework is then applied to assess the uncertainties provided by several satellite data sets (seven over land, five over water), which draw on methods from the empirical to sensitivity analyses to formal error propagation, at 12 Aerosol Robotic Network (AERONET) sites. The AERONET sites are divided into those for which it is expected that the techniques will perform well and those for which some complexity about the site may provide a more severe test. Overall, all techniques show some skill in that larger estimated uncertainties are generally associated with larger observed errors, although they are sometimes poorly calibrated (i.e. too small or too large in magnitude). No technique uniformly performs best. For powerful formal uncertainty propagation approaches such as optimal estimation, the results illustrate some of the difficulties in appropriate population of the covariance matrices required by the technique. When the data sets are confronted by a situation strongly counter to the retrieval forward model (e.g. potentially mixed land-water surfaces or aerosol optical properties outside the family of assumptions), some algorithms fail to provide a retrieval, while others do but with a quantitatively unreliable uncertainty estimate. The discussion suggests paths forward for the refinement of these techniques.

Item URL in elib:https://elib.dlr.de/134299/
Document Type:Article
Title:A review and framework for the evaluation of pixel-level uncertainty estimates in satellite aerosol remote sensing
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Sayer, A.M.NASA, USAUNSPECIFIEDUNSPECIFIED
Govaerts, YvesRayference, BUNSPECIFIEDUNSPECIFIED
Kolmonen, PekkaFMI, FinlandUNSPECIFIEDUNSPECIFIED
Lipponen, AnttiFMI, FinlandUNSPECIFIEDUNSPECIFIED
Luffarelli, MartaRayference, BUNSPECIFIEDUNSPECIFIED
Mielonen, TeroFMI, FinlandUNSPECIFIEDUNSPECIFIED
Patadia, FalguniNASA, USAUNSPECIFIEDUNSPECIFIED
Popp, ThomasUNSPECIFIEDhttps://orcid.org/0000-0002-1970-8733UNSPECIFIED
Povey, AdamUniv. of Oxford, Oxford, UKUNSPECIFIEDUNSPECIFIED
Stebel, KerstinNILU, Kjeller, NUNSPECIFIEDUNSPECIFIED
Witek, Marcin l.JPL, USAUNSPECIFIEDUNSPECIFIED
Date:2020
Journal or Publication Title:Atmospheric Measurement Techniques (AMT)
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:13
DOI:10.5194/amt-13-373-2020
Page Range:pp. 373-404
Publisher:Copernicus Publications
ISSN:1867-1381
Status:Published
Keywords:pixel-level uncertainties, aerosols, satellite remote sensing
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Earth Observation
DLR - Research area:Raumfahrt
DLR - Program:R EO - Earth Observation
DLR - Research theme (Project):R - Remote Sensing and Geo Research
Location: Oberpfaffenhofen
Institutes and Institutions:German Remote Sensing Data Center > Atmosphere
Deposited By: Popp, Dr.rer.nat Thomas
Deposited On:16 Mar 2020 09:36
Last Modified:01 Mar 2021 09:43

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