Sun and Aureole Measurements
Visidyne's new, ground-based instrument (Patent
#7693412) fills the need
in a number of diverse applications for simultaneously
measuring the optical depth (OD) of clouds and the
forward scattering (FS) properties of their particles.
Forward scattering, particularly that associated with
large particles, produces the bright region
surrounding the solar disk known as the aureole.
Analysis of the aureole radiance profile using an
analytic solution formulated by Visidyne yields the
size distribution of the scatterers. Visidyne has
named the combination of two imaging cameras, a solar
tracking mount, data processing software and particle
scattering models, SAM (Solar Aureole
Measurements). SAM sensors do not require any
ancillary measurements or information other than
perhaps synoptic knowledge of the scenes of interest.
These sensors can provide ”truth” data to support the
calibration and validation of cloud algorithms used
with satellite-measured spectral radiances. SAM
sensors also have important applications in cloud and
Villanucci, D., A.
LePage, H. Trabucco, ..., 2008, updated weekly. "SAM
(Sun and Aureole Measurements)", Burlington, MA:
Visidyne, Inc. Data accessible at
Climate (cloud) monitoring
- Cloud physics
- Cloud algorithm cal/val
Column optical depth
- Particle size
SAM sensors can do for clouds what
Aeronet sensors have done for aerosols.
An optional VIS/NIR spectrometer fitted to
a SAM instrument provides coincident solar spectra from
which a number of products follow. Column densities of
atmospheric constituents such as water vapor and ozone can
be produced from the ratios of spectral radiance. The
Angstrom exponent, which is related to the size distribution
of aerosols, is determined from the spectra.