AERONET
Encyclopedia
Sun photometer
A sun photometer is a type of photometer conceived in such a way that it points at the Sun.Recent sun photometers are automated instruments incorporating a Sun-tracking unit, an appropriate opticalsystem, a spectrally filtering device, a photodetector, and a...
s which measure atmospheric aerosol properties. The measurement system is a solar-powered CIMEL Electronique 318A spectral radiometer that measures Sun and sky radiances at
a number of fixed wavelengths within the visible and near-infra red spectrum.
AERONET provides continuous cloud-screened observations of spectral aerosol optical depth
Optical depth
Optical depth, or optical thickness, is a measure of transparency. Optical depth is defined by the negative logarithm of the fraction of radiation that is not scattered or absorbed on a path...
(AOD), precipitable water
Precipitable water column
Precipitable water is the depth of the amount of water in a column of the atmosphere if all the water in that column were precipitated as rain. As a depth, the precipitable water is measured in millimeters or inches.- Measurement :...
, and inversion aerosol products in diverse aerosol
regimes. Inversion products are retrieved from almucantar
Almucantar
An Almucantar, also spelled almucantarat or almacantara, is a circle on the celestial sphere parallel to the horizon. Two stars that lie the same almucantar have the same altitude.-Almucantar staff:...
scans of radiance as a function of scattering angle and include products such as aerosol volume size distribution, aerosol complex refractive index
Refractive index
In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....
, optical absorption (single scattering albedo
Single scattering albedo
Single scattering albedo - the ratio of scattering efficiency to total extinction efficiency . Most often it is defined for small-particle scattering of electromagnetic waves...
) and the aerosol scattering phase function. All these products represent an average of the total aerosol column within the atmosphere.
The aerosol properties are retrieved via an inversion algorithm developed by Dubovik and King (2000).
Further algorithms were developed, for example, by Dubovik et al. (2006) to take into account non-spherical shapes of aerosol particles such as mineral dust.
AERONET is an observing system in the NOAA Observing System Architecture
NOAA Observing System Architecture
*The NOAA Observing System Architecture is a collection of over 100 of NOAA's environmental datasets.*NOSA was established to develop an observational architecture that helps NOAA:...
.