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Trend Estimates of AERONET-Observed and Model-Simulated AOTs Between 1993 and 2013Recently, temporal changes in Aerosol Optical Thickness (AOT) have been investigated based on model simulations, satellite and ground-based observations. Most AOT trend studies used monthly or annual arithmetic means that discard details of the generally right-skewed AOT distributions. Potentially, such results can be biased by extreme values (including outliers). This study additionally uses percentiles (i.e., the lowest 5%, 25%, 50%, 75% and 95% of the monthly cumulative distributions fitted to Aerosol Robotic Network (AERONET)-observed and ECHAM/MESSy Atmospheric Chemistry (EMAC)-model simulated AOTs) that are less affected by outliers caused by measurement error, cloud contamination and occasional extreme aerosol events. Since the limited statistical representativeness of monthly percentiles and means can lead to bias, this study adopts the number of observations as a weighting factor, which improves the statistical robustness of trend estimates. By analyzing the aerosol composition of AERONET-observed and EMAC-simulated AOTs in selected regions of interest, we distinguish the dominant aerosol types and investigate the causes of regional AOT trends. The simulated and observed trends are generally consistent with a high correlation coefficient (R = 0.89) and small bias (slope+/-2(sigma) = 0.75 +/- 0.19). A significant decrease in EMAC-decomposed AOTs by water-soluble compounds and black carbon is found over the USA and the EU due to environmental regulation. In particular, a clear reversal in the AERONET AOT trend percentiles is found over the USA, probably related to the AOT diurnal cycle and the frequency of wildfires. In most of the selected regions of interest, EMAC-simulated trends are mainly attributed to the significant changes of the dominant aerosols; e.g., significant decrease in sea salt and water soluble compounds over Central America, increase in dust over Northern Africa and Middle East, and decrease in black carbon and organic carbon over Australia.
Document ID
20160005735
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Yoon, J.
(Max-Planck-Inst. fuer Chemie Mainz, Germany)
Pozzer, A.
(Max-Planck-Inst. fuer Chemie Mainz, Germany)
Chang, D. Y.
(Max-Planck-Inst. fuer Chemie Mainz, Germany)
Lelieveld, J.
(Max-Planck-Inst. fuer Chemie Mainz, Germany)
Kim, J.
(Yonsei Univ. Seoul, Korea, Republic of)
Kim, M.
(Yonsei Univ. Seoul, Korea, Republic of)
Lee, Y. G.
(Chungnam National Univ. Korea, Republic of)
Koo, J.-H.
(Toronto Univ. Ontario, Canada)
Lee, J.
(Maryland Univ. College Park, MD, United States)
Moon, K. J.
(National Institute of Environmental Research Incheon, Korea, Republic of)
Date Acquired
May 3, 2016
Publication Date
October 23, 2015
Publication Information
Publication: Atmospheric Environment
Publisher: Elsevier
Volume: 125
Issue: Part A
ISSN: 1352-2310
Subject Category
Earth Resources And Remote Sensing
Environment Pollution
Report/Patent Number
GSFC-E-DAA-TN31778
Funding Number(s)
CONTRACT_GRANT: NNX12AD03A
Distribution Limits
Public
Copyright
Other
Keywords
AERONET
trend estimates
aerosol optical thickness

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