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The MFRSR takes spectral measurements of direct normal, diffuse
horizontal, and total horizontal solar irradiances. These
measurements are at nominal wavelengths of 415, 500, 615, 673,
870, and 940 nm. The measurements are made at a user specified
time interval; typically this interval is about one minute or
less, at the SGP site, the sampling interval is 20 seconds. From
such measurements, one may infer the atmosphere's optical depth
at the wavelengths mentioned above. In turn, these optical
depths may be used to derive information about the column
abundances of ozone and water vapor (Michalsky et al. 1995), as
well as aerosol (Michalsky et al. 1994) and other atmospheric
constituents.
A silicon detector is also part of the MFRSR. This broadband
detector provides a measure of the broadband direct normal,
diffuse horizontal, and total horizontal solar
irradiances. These quantities are uncalibrated and reported in
units of "counts." An MFRSR head that is mounted to look
vertically downward can measure upwelling spectral irradiances
(obviously at the same wavelengths as the MFRSR!). In the ARM
system, this instrument is called an "MFR". At the SGP there are
two MFRs; one mounted at the 10 m height and the other at 25
m. At the NSA sites, the MFRs are mounted at 10 m.
Additional information available at
"http://www.arm.gov/docs/instruments.html"
[Summary provided by ARM]
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