Aerosol Optical Depth Measurements Available as Value-Added Product

Published: 1 December 2011

aod figure 1 — Cloud-screened AOD at five wavelengths (top) and Angstrom exponent (bottom) over a three-month time period at the Black Forest, Germany deployment.

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.

aod figure 2 — Same measurements as the data plot above, but displaying a close-up over one day to show diurnal variation.

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.

More information on AOD is available at the VAP web page. To access these data, log in to the Data Archive. (Go here to request an account.)

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The ARM Climate Research Facility is a DOE Office of Science user facility. The ARM Facility is operated by nine DOE national laboratories, including .