The core purpose of ARM is to reduce uncertainties in climate model predictions. A dominant source of uncertainty in these models is the radiative impact of aerosols, which has spawned a major effort in ARM to measure aerosol properties.

The Aerosol Optical Depth (AOD) value-added product (VAP) is concerned with several important aerosol radiative properties. The most important of these is the AOD, which is a measure of the total aerosol burden in the atmosphere. The spectral dependence of AOD, typically described by the Angstrom exponent, is also an indicator of particle size, with large particles having Angstrom exponent values near zero and smaller particles exhibiting larger Angstrom exponent values. Improved knowledge of these basic aerosol properties will help reduce the uncertainties associated with aerosol effects in climate models.

The AODs have been derived from the MFRSR, NIMFR and SASHE instruments. For more information about these products, please refer to the MFRSR/NIMFR technical report and SASHE technical report or to the output product pages linked below.