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ASTAR 2007

last modified 2007-06-26 23:54
Contributors: jfb

ASTAR: Arctic Study of Tropospheric Aerosols, Clouds and Radiation Spring 2007

When 2007-03-24 12:10 to
2007-04-17 13:10
Where Svalbard, Norway
Contact Name Dr. Andreas Herber
Contact Email
Contact Phone +4947148311489
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Overall Project Description

The ASTAR 2007 campaign was conducted from March 24 - April 17th, 2007. The field activities are now over, but data analysis and interpretation has just begun. Further information can be found at the official campaign site operated by Andreas Minikin.

At the left see Photos (Please email photos to JFB or contact directly to have permissions)

The strong intrusions of polluted air masses during Arctic Haze events are of specific interest for determining the anthropogenic influence on the radiative balance including cloud formation processes. However, also the transition from Arctic Haze to the period of the year where the high latitudes are more or less "protected" from long-range transport of air masses from lower latitudes is of interest. This is resulted by changes in transport patterns and may cause variations in the flux of trace gases and particles into the Arctic reservoirs. Therefore, this project is centered on two aircraft measurement campaigns, scheduled from 2004 to 2007. The Arctic measurement program will focus on physical, chemical and optical properties of tropospheric aerosol and cloud micro-physical properties, For the Arctic; the main focus of the project is to provide an observational over-determined data set, which is necessary to improve the assessment of the aerosol direct and indirect effects on the Arctic radiative balance. This will be achieved by utilizing unique aircraft instrumental payloads, addressing both aerosol and cloud measurements, combined with ground-based and satellite observations and by using appropriate modeling tools. Measurements will be performed during periods of Arctic Haze as well as during the transition to the clean Arctic summer conditions.

The scientific objectives of the Arctic campaigns are focused on two major issues:

Determination of the vertical structure of the chemical, physical and optical properties of Arctic aerosol particles, including solar radiative closure between observed and calculated aerosol properties (direct climate effect)

  • Characterization of the Arctic aerosol spatial distribution and variability based on airborne in-situ observations of physical, chemical and optical aerosol properties.
  • Closure calculations on the solar and terrestrial radiative balance and climate implications by the Arctic aerosol (Arctic Haze versus background conditions).
  • Closure experiment of between measured bulk optical properties and respective simulations based on observed physical and chemical aerosol properties.
  • Improvement of understanding of aerosol life cycle and transport pathways in the Arctic.
  • Determination of the size dependent aerosol chemical composition and fractionation of volatile, semi-volatile and non-volatile particles.
  • Study of exchange processes of air between the free troposphere and boundary layer
  • Evaluation of the parameterization of aerosol processes in global and regional chemistry-climate models against the observations.
  • Study temporal and spatial variability of the aerosol number densities and size distribution with respect to the long-term ground-based measurements at Ny-Ă…lesund, Spitsbergen.
  • Validation of the satellite based lidar (CALIPSO) and aerosol optical depth measurements (ATSR-2, ENVISAT/SCIAMACHY, ILAS II, MERIS, MODIS, OMI, SAGE III, SeaWiFS), based on ground-based and airborne measurements.
  • Determination of regional extension of aerosol properties by satellite retrievals (ENVISAT/SCIAMACHY, MERIS, MODIS, SeaWiFS).

Investigation of cloud microphysical and optical properties in the Arctic as a function of different tropospheric aerosol load and the regional extend of aerosol and cloud structures (indirect climate effect)

  • Comparison of spectral radiative properties (reflectance, absorption, transmission) of Arctic ice and mixed-phase clouds compared to pure water clouds.

  • Study of in-cloud scattering related to crystal shape in ice-phase containing clouds.

  • Activation of aerosol particles into cloud elements in the Arctic environment: of particular interest is the ice nucleation (heterogeneous process) with special attention paid to mixed-phase clouds.

  • Study of the high variability of cloud macro- (multiple cloud layers, thin stratus) as well as microphysical properties in the Arctic with respect to atmospheric conditions (temperature, aerosol properties, adiabatic or non-adiabatic conditions).

  • Validation/derivation of remote sensing parameters e.g. from depolarization lidar on POLAR 2 or CALIPSO satellite platform with in-situ measured cloud microphysical an optical parameters.

  • Validation of cloud products (hemispheric reflectance, cloud optical thickness, cloud top height) of satellite retrievals.

  • Evaluation and improvement of cloud process models, climate model parameterization of Arctic clouds and radiation processes, as well as remote sensing products of surface characteristics by using the obtained cloud microphysical/optical data.

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