POLAR-AOD (Aerosols Optical Depth in Polar regions) is a project aimed at obtaining, through international collaboration, an improved understanding and characterization of polar aerosols and their radiative effects on climate.

Polar regions represent a sensitive ecosystems, which are susceptible to even small changes in the local climate. The special conditions of usually high surface albedo and low solar elevations cause enhanced aerosol/cloud effects due to multiple scattering, magnifying their radiative impact. So, direct and indirect aerosol effects can produce significant regional radiative forcing. Theoretical calculations suggest that the polar regions are peculiar in this regard, showing that radiative forcing can change sign depending on chemical species, surface properties and solar geometry. Moreover, even slight changes in cloud microphysical or physical properties resulting from interactions with aerosols are likely to perturb the climate of the high latitude regions because clouds profoundly impact the radiation balance there.

Unfortunately, satellite data are not yet useful at high latitudes for deriving aerosol properties. Therefore, to meet the scientific goal of producing a global aerosol climatology into the polar regions, aerosol observations that are currently being made at several Antarctic and Arctic sites should be integrated in an overall data base. POLAR-AOD aims to coordinate international efforts to assure that consistent, high quality data from the network be assimilated and be made available to the scientific community. Having a network essentially in place, this action will consist mainly in:

1. Establish an archive of polar data and metadata.
2. Establish a website to give easy access to these data, bibliographical materials, with links to related sites.
3. Determine reliable procedures for analyzing sun-photometric and sun-radiometric data, paying particular attention to the specific conditions of the polar regions.
4. Define calibration procedures between the various sun-radiometers operating in Antarctica and Arctic, in order to achieve homogeneous AOD evaluations in the various stations.
5. Convene international workshops for presentations of results from the various polar programs, discuss common strategies, future needs/goals, protocols, logistics of inter-calibration activities, data format, etc.