Publications

Aerosol Optical Properties and Type Retrieval via Machine Learning and an All-Sky Imager

Logothetis, Stavros-Andreas; Giannaklis, Christos-Panagiotis; Salamalikis, Vasileios; Tzoumanikas, Panagiotis; Raptis, Panagiotis-Ioannis; Amiridis, Vassilis; Eleftheratos, Kostas; Kazantzidis, Andreas

This study investigates the applicability of using the sky information from an all-sky imager (ASI) to retrieve aerosol optical properties and type. Sky information from the ASI, in terms of Red-Green-Blue (RGB) channels and sun saturation area, are imported into a supervised machine learning algorithm for estimating five different aerosol optical properties related to aerosol burden (aerosol optical depth, AOD at 440, 500 and 675 nm) and size (Ångström Exponent at 440–675 nm, and Fine Mode Fraction at 500 nm). The retrieved aerosol optical properties are compared against reference measurements from the AERONET station, showing adequate agreement (R: 0.89–0.95). The AOD errors increased for higher AOD values, whereas for AE and FMF, the biases increased for coarse particles. Regarding aerosol type classification, the retrieved properties can capture 77.5% of the total aerosol type cases, with excellent results for dust identification (>95% of the cases). The results of this work promote ASI as a valuable tool for aerosol optical properties and type retrieval.

MDPI

Aerosol optical properties and distribution during the extreme Arctic haze event in spring 2006.

Myhre, C.L.; Toledano, C.; Myhre, G.; Stebel, K.; Frioud, M.; Yttri, K.E.; Johnsrud, M.

Aerosol optical properties and distribution during the extreme Arctic haze event in spring 2006.

Myhre, C.L.; Toledano, C.; Stebel, K.; Frioud, M.; Yttri, K.E.; Johnsrud, M.

Aerosol microphysical effects on cloud fraction over the nighttime Arctic Ocean.

Zamora, L. M.; Kahn, R. A.; Stohl, A.; Eckhardt, S.

Aerosol measurements and atmospheric correction at high northern latitudes: a comparison of MERIS data. Abstract. NILU F

Engelsen, O.; Sorensen, K.; Hokedal, J.

Aerosol indirect effects on the nighttime Arctic Ocean surface from thin, predominantly liquid clouds.

Zamora, L. M.; Kahn, R. A.; Eckhardt, S.; McComiskey, A.; Sawamura, P.; Moore, R.; Stohl, A.

Aerosol hygroscopicity influenced by seasonal chemical composition variations in the Arctic region

Kang, Hyojin; Jung, Chang Hoon; Lee, Bang Young; Krejci, Radovan; Heslin-Rees, Dominic; Aas, Wenche; Yoon, Young Jun

In this study, we quantified aerosol hygroscopicity parameter using aerosol microphysical observation data (κphy), analyzing monthly and seasonal trends in κphy by correlating it with aerosol chemical composition over 6 years from April 2007 to March 2013 at the Zeppelin Observatory in Svalbard, Arctic region. The monthly mean κphy value exhibited distinct seasonal variations, remaining high from winter to spring, reaching its minimum in summer, followed by an increase in fall, and maintaining elevated levels in winter. To verify the reliability of κphy, we employed the hygroscopicity parameter calculated from chemical composition data (κchem). The chemical composition and PM2.5 mass concentration required to calculate κchem was obtained through Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) reanalysis data and the calculation of κchem assumed that Arctic aerosols comprise only five species: black carbon (BC), organic matter (OM), ammonium sulfate (AS), sea salt aerosol less than a diameter of 2.5 μm (SSA2.5), and dust aerosol less than a diameter of 2.5 μm (Dust2.5). The κchem had no distinct correlation but had a similar seasonal trend compared to κphy. The κchem value followed a trend of SSA2.5 and was much higher by a factor of 1.6 ± 0.3 than κphy on average, due to a large proportion of SSA2.5 mass concentration in MERRA-2 reanalysis data. This may be due to the overestimation of sea salt aerosols in MERRA-2 reanalysis. The relationship between monthly mean κphy and the chemical composition used to calculate κchem was also analyzed. The elevated κphy from October to February resulted from the dominant influence of SSA2.5, while the maximum κphy in March was concurrently influenced by increasing AS and Dust2.5 associated with long-range transport from mid-latitude regions during Arctic haze periods and by SSA mass concentration obtained from in-situ sampling, which remained high from the preceding winter. The relatively low κphy from April to September can be attributed to low SSA2.5 and the dominance of organic compounds in the Arctic summer. Either natural sources such as those of marine and terrestrial biogenic origin or long-range-transported aerosols may contribute to the increase in organic aerosols in summer, potentially influencing the reduction in κphy of atmospheric aerosols. To our knowledge, this is the first study to analyze the monthly and seasonal variation of aerosol hygroscopicity calculated using long-term microphysical data, and this result provides evidence that changes in monthly and seasonal hygroscopicity variation occur depending on chemical composition.

Elsevier

Aerosol decadal trends - Part 2: In-situ aerosol particle number concentrations at GAW and ACTRIS stations.

Asmi, A.; Collaud Coen, M.; Ogren, J. A.; Andrews, E.; Sheridan, P.; Jefferson, A.; Weingartner, E.; Baltensperger, U.; Bukowiecki, N.; Lihavainen, H.; Kivekäs, N.; Asmi, E.; Aalto, P. P.; Kulmala, M.; Wiedensohler, A.; Birmili, W.; Hamed, A.; O'Dowd, C.; G Jennings, S.; Weller, R.; Flentje, H.; Fjaeraa, A. M.; Fiebig, M.; Myhre, C. L.; Hallar, A. G.; Swietlicki, E.; Kristensson, A.; Laj, P.

Aerosol composition and sources in the Central Arctic Ocean during ASCOS.

Chang, R. Y.-W.; Leck, C.; Graus, M.; Müller, M.; Paatero, J.; Burkhart, J. F.; Stohl, A.; Orr, L. H.; Hayden, K.; Li, S.-M.; Hansel, A.; Tjernström, M.; Leaitch, W. R.; Abbatt, J. P. D.

Aerosol chemical, physical, and optical properties over an ice-free region of the Arctic during the International Chemistry Experiment in the Arctic LOwer Troposphere (ICEALOT).

Bates, T.S.; Quinn, P.K.; Coffman, D.; Covert, D.S.; Burkhart, J.F.; Russell, L.M.

Aerosol characterization at the sub-Arctic site Andenes (69°N, 16°E), by the analysis of columnar optical properties.

Rodríguez, E.; Toledano, C.; Cachorro, V.E.; Ortiz, P.; Stebel, K.; Berjón, A.; Blindheim, S.; Gausa, M.; de Frutos, A.M.

Aerosol black carbon at five background measurement sites over Finland, a gateway to the Arctic.

Hyvärinen, A.-P.; Kolmonen, P.; Kerminen, V.-M.; Virkkula, A.; Leskinen, Komppula, M.; Hatakkaa, J.; Burkhart, J.; Stohl, A.; Aalto, P.; Kulmala, M.; Lehtinen, K.E.J.; Viisanen, Y.; Lihavainen, H.

Aerosol and dynamical contributions to cloud droplet formation in Arctic low-level clouds

Motos, Ghislain; Freitas, Gabriel; Georgakaki, Paraskevi; Wieder, Jörg; Li, Guangyu; Aas, Wenche; Lunder, Chris Rene; Krejci, Radovan; Pasquier, Julie Thérèse; Henneberger, Jan; David, Robert Oscar; Ritter, Christoph; Mohr, Claudia; Zieger, Paul; Nenes, Athanasios