Airborne particles are drawn into a chamber. After closing the chamber the particles are irradiated with broadband shortwave radiation. The mean shortwave volume absorption coefficient of the particles is calculated from the measured pressure change with time within the chamber. The method has been calibrated using water vapor. The detection limit is +/-2 x 10(-6)/m in terms of the volume absorption coefficient. There is very good agreement between the calorimetric and a new photometric absorption measurement. Advantages and disadvantages of both methods are discussed at the end of the paper.

A new radiometer is described which simplifies measurement of the radiation supply of solar wavelengths. Two methods of measuring the radiant energy absorbed by aerosol particles are described: A photometric technique is used for particles collected on filters, and a calorimetric technique is used for in situ measurements. Data collected with the radiometer and the light absorption techniques yield the heating rate of the atmosphere due to light absorption by the particles. Sample measurements show substantial atmospheric temperature increases due to absorption, especially in industrial regions.

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