title: Remote sensing of aerosols in the Arctic for an evaluation of global climate model simulations.
abstract: In this study Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua retrievals of aerosol optical thickness (AOT) at 555 nm are compared to Sun photometer measurements from Svalbard for a period of 9 years. For the 642 daily coincident measurements that were obtained, MODIS AOT generally varies within the predicted uncertainty of the retrieval over ocean (ΔAOT = ±0.03 ± 0.05 · AOT). The results from the remote sensing have been used to examine the accuracy in estimates of aerosol optical properties in the Arctic, generated by global climate models and from in situ measurements at the Zeppelin station, Svalbard. AOT simulated with the Norwegian Earth System Model/Community Atmosphere Model version 4 Oslo global climate model does not reproduce the observed seasonal variability of the Arctic aerosol. The model overestimates clear-sky AOT by nearly a factor of 2 for the background summer season, while tending to underestimate the values in the spring season. Furthermore, large differences in all-sky AOT of up to 1 order of magnitude are found for the Coupled Model Intercomparison Project phase 5 model ensemble for the spring and summer seasons. Large differences between satellite/ground-based remote sensing of AOT and AOT estimated from dry and humidified scattering coefficients are found for the subarctic marine boundary layer in summer.
  
  
  CONCLUSIONS
  Remote sensing of AOT is very useful in validation of climate models.
authors.affiliation: Department of Applied Environmental Science, Stockholm University Stockholm, Sweden.
authors.forename: Paul
authors.initials: P
authors.lastname: Glantz
authors.affiliation: Institute of Space and Atmospheric Studies, University of Saskatchewan Saskatoon, Saskatchewan, Canada.
authors.forename: Adam
authors.initials: A
authors.lastname: Bourassa
authors.affiliation: Alfred Wegener Institute for Polar and Marine Research Bremerhaven, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Herber
authors.affiliation: ECMWF Reading, UK ; Norwegian Meteorological Institute Oslo, Norway.
authors.forename: Trond
authors.initials: T
authors.lastname: Iversen
authors.affiliation: Department of Meteorology, Stockholm University Stockholm, Sweden.
authors.forename: Johannes
authors.initials: J
authors.lastname: Karlsson
authors.affiliation: Norwegian Meteorological Institute Oslo, Norway.
authors.forename: Alf
authors.initials: A
authors.lastname: Kirkevåg
authors.affiliation: Alfred Wegener Institute for Polar and Marine Research Bremerhaven, Germany.
authors.forename: Marion
authors.initials: M
authors.lastname: Maturilli
authors.affiliation: Norwegian Meteorological Institute Oslo, Norway.
authors.forename: Øyvind
authors.initials: Ø
authors.lastname: Seland
authors.affiliation: Norwegian Institute for Air Research Oslo, Norway.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Stebel
authors.affiliation: National Supercomputer Centre, Linköping University Linköping, Sweden.
authors.forename: Hamish
authors.initials: H
authors.lastname: Struthers
authors.affiliation: Department of Applied Environmental Science, Stockholm University Stockholm, Sweden.
authors.forename: Matthias
authors.initials: M
authors.lastname: Tesche
authors.affiliation: NASA Langley Research Center Hampton, Virginia, USA.
authors.forename: Larry
authors.initials: L
authors.lastname: Thomason
keywords: Arctic aerosol; aerosol optical thickness; marine aerosol; model simulation; remote sensing of aerosol
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references.pmid: 11539801
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references.pmid: 22767926