Aerosol optical depth (AOD) measures total aerosol burden in the atmosphere. The spectral dependence of AOD, typically described by the Angstrom exponent, is also an indicator of particle size. Small Angstrom exponent values (near zero) indicate presence of large particles, and vice versa.
The newly developed AOD value-added product (VAP) provides both the wavelength-dependent values of AOD and the Angstrom exponent from five spectrally resolved measurements gathered by the multifilter rotating shadowband radiometer (MFRSR). This VAP uses MFRSR-based algorithms originally developed by Michalsky et al. and applied to over ten years of AOD measurements at the well-established ARM Southern Great Plains (SGP) site. Recently, these algorithms were modified for use at diverse locations occupied by the ARM Mobile Facilities (AMF), including Point Reyes, California; Black Forest, Germany; and Graciosa Island, Azores.
The figures below show daily and 3-month time series of cloud-screened AOD and Angstrom exponent at the Black Forest site in Germany collected on a 20-second interval during daylight hours.