In-situ measurements of aerosol absorption with a resonant cw laser spectrophone.

The absorption of radiation by aerosol particles is impor­ tant to radiative transfer processes in the atmosphere; their effects on the earth's climate and on the operation of electrooptical devices are examples. Since atmospheric aerosols are known to contain significant amounts of volatile compo­ nents, it is desirable to measure their absorption in situ or, in other words, without removing them from their natural en­ vironment. Measurement of aerosol absorption in situ is difficult and to date has only been done definitively by indi­ rect techniques. The spectrophone holds promise for making these measurements more directly, bypassing alto­ gether measurements of particle shape, size, and complex refractive index. Herein are reported results obtained using a calibrated in-situ spectrophone compared with results calculated from nearly simultaneous measurements of particle size distributions for dust samples consisting of ground crys-