Trend estimates of AERONET-observed and model-simulated AOTs between 1993 and 2013

J. Yoon, A. Pozzer, D. Y. Chang, J. Lelieveld, Jhoon Kim, M. Kim, Y. G. Lee, Ja-Ho Koo, J. Lee, K. J. Moon

Research output: Contribution to journalArticle

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Abstract

Recently, 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±2σ = 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.

Original languageEnglish
Pages (from-to)33-47
Number of pages15
JournalAtmospheric Environment
Volume125
DOIs
Publication statusPublished - 2016 Jan 1

Fingerprint

aerosol
atmospheric chemistry
black carbon
outlier
AERONET
trend
aerosol composition
sea salt
wildfire
organic carbon
dust
seawater
simulation
water

All Science Journal Classification (ASJC) codes

  • Environmental Science(all)
  • Atmospheric Science

Cite this

Yoon, J. ; Pozzer, A. ; Chang, D. Y. ; Lelieveld, J. ; Kim, Jhoon ; Kim, M. ; Lee, Y. G. ; Koo, Ja-Ho ; Lee, J. ; Moon, K. J. / Trend estimates of AERONET-observed and model-simulated AOTs between 1993 and 2013. In: Atmospheric Environment. 2016 ; Vol. 125. pp. 33-47.
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abstract = "Recently, 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±2σ = 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.",
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Yoon, J, Pozzer, A, Chang, DY, Lelieveld, J, Kim, J, Kim, M, Lee, YG, Koo, J-H, Lee, J & Moon, KJ 2016, 'Trend estimates of AERONET-observed and model-simulated AOTs between 1993 and 2013', Atmospheric Environment, vol. 125, pp. 33-47. https://doi.org/10.1016/j.atmosenv.2015.10.058

Trend estimates of AERONET-observed and model-simulated AOTs between 1993 and 2013. / Yoon, J.; Pozzer, A.; Chang, D. Y.; Lelieveld, J.; Kim, Jhoon; Kim, M.; Lee, Y. G.; Koo, Ja-Ho; Lee, J.; Moon, K. J.

In: Atmospheric Environment, Vol. 125, 01.01.2016, p. 33-47.

Research output: Contribution to journalArticle

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T1 - Trend estimates of AERONET-observed and model-simulated AOTs between 1993 and 2013

AU - Yoon, J.

AU - Pozzer, A.

AU - Chang, D. Y.

AU - Lelieveld, J.

AU - Kim, Jhoon

AU - Kim, M.

AU - Lee, Y. G.

AU - Koo, Ja-Ho

AU - Lee, J.

AU - Moon, K. J.

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