Validation and empirical correction of MODIS AOT and AE over ocean
We present a validation study of Collection 5 MODIS level 2 Aqua and Terra AOT (aerosol optical thickness) and AE (Ångström exponent) over ocean by comparison to coastal and island AERONET (AErosol RObotic NETwork) sites for the years 2003–2009. We show that MODIS (MODerate-resolution Imaging Spectr...
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ftdoajarticles:oai:doaj.org/article:0a3920f4ccbc486390c6487aa326aeaf 2023-05-15T13:06:38+02:00 Validation and empirical correction of MODIS AOT and AE over ocean N. A. J. Schutgens M. Nakata T. Nakajima 2013-09-01T00:00:00Z https://doi.org/10.5194/amt-6-2455-2013 https://doaj.org/article/0a3920f4ccbc486390c6487aa326aeaf EN eng Copernicus Publications http://www.atmos-meas-tech.net/6/2455/2013/amt-6-2455-2013.pdf https://doaj.org/toc/1867-1381 https://doaj.org/toc/1867-8548 doi:10.5194/amt-6-2455-2013 1867-1381 1867-8548 https://doaj.org/article/0a3920f4ccbc486390c6487aa326aeaf Atmospheric Measurement Techniques, Vol 6, Iss 9, Pp 2455-2475 (2013) Environmental engineering TA170-171 Earthwork. Foundations TA715-787 article 2013 ftdoajarticles https://doi.org/10.5194/amt-6-2455-2013 2022-12-31T14:58:09Z We present a validation study of Collection 5 MODIS level 2 Aqua and Terra AOT (aerosol optical thickness) and AE (Ångström exponent) over ocean by comparison to coastal and island AERONET (AErosol RObotic NETwork) sites for the years 2003–2009. We show that MODIS (MODerate-resolution Imaging Spectroradiometer) AOT exhibits significant biases due to wind speed and cloudiness of the observed scene, while MODIS AE, although overall unbiased, exhibits less spatial contrast on global scales than the AERONET observations. The same behaviour can be seen when MODIS AOT is compared against Maritime Aerosol Network (MAN) data, suggesting that the spatial coverage of our datasets does not preclude global conclusions. Thus, we develop empirical correction formulae for MODIS AOT and AE that significantly improve agreement of MODIS and AERONET observations. We show these correction formulae to be robust. Finally, we study random errors in the corrected MODIS AOT and AE and show that they mainly depend on AOT itself, although small contributions are present due to wind speed and cloud fraction in AOT random errors and due to AE and cloud fraction in AE random errors. Our analysis yields significantly higher random AOT errors than the official MODIS error estimate (0.03 + 0.05 τ), while random AE errors are smaller than might be expected. This new dataset of bias-corrected MODIS AOT and AE over ocean is intended for aerosol model validation and assimilation studies, but also has consequences as a stand-alone observational product. For instance, the corrected dataset suggests that much less fine mode aerosol is transported across the Pacific and Atlantic oceans. Article in Journal/Newspaper Aerosol Robotic Network Directory of Open Access Journals: DOAJ Articles Pacific Atmospheric Measurement Techniques 6 9 2455 2475 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Environmental engineering TA170-171 Earthwork. Foundations TA715-787 |
spellingShingle |
Environmental engineering TA170-171 Earthwork. Foundations TA715-787 N. A. J. Schutgens M. Nakata T. Nakajima Validation and empirical correction of MODIS AOT and AE over ocean |
topic_facet |
Environmental engineering TA170-171 Earthwork. Foundations TA715-787 |
description |
We present a validation study of Collection 5 MODIS level 2 Aqua and Terra AOT (aerosol optical thickness) and AE (Ångström exponent) over ocean by comparison to coastal and island AERONET (AErosol RObotic NETwork) sites for the years 2003–2009. We show that MODIS (MODerate-resolution Imaging Spectroradiometer) AOT exhibits significant biases due to wind speed and cloudiness of the observed scene, while MODIS AE, although overall unbiased, exhibits less spatial contrast on global scales than the AERONET observations. The same behaviour can be seen when MODIS AOT is compared against Maritime Aerosol Network (MAN) data, suggesting that the spatial coverage of our datasets does not preclude global conclusions. Thus, we develop empirical correction formulae for MODIS AOT and AE that significantly improve agreement of MODIS and AERONET observations. We show these correction formulae to be robust. Finally, we study random errors in the corrected MODIS AOT and AE and show that they mainly depend on AOT itself, although small contributions are present due to wind speed and cloud fraction in AOT random errors and due to AE and cloud fraction in AE random errors. Our analysis yields significantly higher random AOT errors than the official MODIS error estimate (0.03 + 0.05 τ), while random AE errors are smaller than might be expected. This new dataset of bias-corrected MODIS AOT and AE over ocean is intended for aerosol model validation and assimilation studies, but also has consequences as a stand-alone observational product. For instance, the corrected dataset suggests that much less fine mode aerosol is transported across the Pacific and Atlantic oceans. |
format |
Article in Journal/Newspaper |
author |
N. A. J. Schutgens M. Nakata T. Nakajima |
author_facet |
N. A. J. Schutgens M. Nakata T. Nakajima |
author_sort |
N. A. J. Schutgens |
title |
Validation and empirical correction of MODIS AOT and AE over ocean |
title_short |
Validation and empirical correction of MODIS AOT and AE over ocean |
title_full |
Validation and empirical correction of MODIS AOT and AE over ocean |
title_fullStr |
Validation and empirical correction of MODIS AOT and AE over ocean |
title_full_unstemmed |
Validation and empirical correction of MODIS AOT and AE over ocean |
title_sort |
validation and empirical correction of modis aot and ae over ocean |
publisher |
Copernicus Publications |
publishDate |
2013 |
url |
https://doi.org/10.5194/amt-6-2455-2013 https://doaj.org/article/0a3920f4ccbc486390c6487aa326aeaf |
geographic |
Pacific |
geographic_facet |
Pacific |
genre |
Aerosol Robotic Network |
genre_facet |
Aerosol Robotic Network |
op_source |
Atmospheric Measurement Techniques, Vol 6, Iss 9, Pp 2455-2475 (2013) |
op_relation |
http://www.atmos-meas-tech.net/6/2455/2013/amt-6-2455-2013.pdf https://doaj.org/toc/1867-1381 https://doaj.org/toc/1867-8548 doi:10.5194/amt-6-2455-2013 1867-1381 1867-8548 https://doaj.org/article/0a3920f4ccbc486390c6487aa326aeaf |
op_doi |
https://doi.org/10.5194/amt-6-2455-2013 |
container_title |
Atmospheric Measurement Techniques |
container_volume |
6 |
container_issue |
9 |
container_start_page |
2455 |
op_container_end_page |
2475 |
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1766014423263084544 |