On the use of satellites to obtain information on the occurrence of natural and anthropogenic aerosols over the boreal eurasian forest
The ALANIS-Aerosols project is a feasibility study on the use of existing satellite data for discriminating between natural aerosols emitted by boreal Eurasian forests and long-range transported anthropogenic aerosols. In this paper an overview is provided of different satellite products which are potentially useful to obtain this kind of information. Approaches that have been followed in the past are briefly summarized. Secondary production of aerosols from their precursor gases, in particular biogenic volatile organic compounds which play an important role in the formation of new particles through nucleation, is briefly discussed. These newly formed particles are initially too small to observe directly with optical instruments used for earth observation (EO) but through the use of proxies information can be obtained on global nucleation mode aerosol concentrations. Next we focus on aerosols with particle sizes in the optically active size range, roughly particles with a diameter larger than 50-100 nm, depending on wavelength. These particles can be observed with EO instruments as well as using several different types of in situ observations. The satellite data used are aerosol properties retrieved from the Advanced Along Track Scanning Radiometer (AATSR, flying on ENVISAT since 2002) using both the forward and nadir view with the AATSR dual view algorithm (ADV). Ground-based in situ data used here are aerosol properties measured in Hyytiälä, Finland. These observations are complemented with model calculations using the global atmospheric aerosol and chemistry model GLOMAP. Examples show the complementarity of different data sources to obtain information on the temporal and spatial information on the nature of aerosols over the Boreal forest.