Several methods to measure aerosols already exist, each with it’s own pros and cons. On this page the most important methods used are described briefly. The main problem at this point is the characterisation of aerosols at a distance. SPEX and iSPEX allow a major improvement in this field.
Sahara zand boven de kust van West Afrika. Bron: http://eoimages.gsfc.nasa.gov
Current methods of measuring from space:
A measurement from a satelite in space provides information about all places on earth. Because the orbit of a satelite allows the instrument to do aerosol measurements once a day for each place, it is not the best way to monitor changes in aerosol properties over time. That is why space based and ground based instruments are best when used as complementary to eachother.
Current methods of measuring from the ground:
- RIVM: LML and other PM 10/2.5 measurements
- Aeronet sunphotometer
- Lidar
A groundbased measurement only offers local information. In fact, any method allways has its limitation. For example, PM 10 (or 2.5) measurements only measure locally the number of particles smaller than 10 (or 2.5) micrometer. The exact size distribution, or (chemical) composition of the aerosols is not measured with this method. Additional measurements are needed to retrieve this information.
iSPEX method:
The iSPEX instrument is derived from the SPEX design. The iSPEX method to measure aerosols with spectropolarimetry is also much like the way we do this with SPEX, except that with iSPEX we have a less accurate instrument taking more measurements at much more places. This larger number of measurements and locations can be reached with the use of crowdsourcing.
