Abstract:
The Atmospheric Radiation Measurement (ARM) Program is the largest global
change research program supported by the U.S. Department of Energy (DOE). ARM
scientists focus on obtaining field measurements and developing models to
better understand the processes that control solar and thermal infrared
radiative transfer in the atmosphere (especially in clouds) and at the earth's
... surface.
The URL for the ARM Data Archive is http://www.archive.arm.gov/. The URL for
general information about the ARM program is http://www.arm.gov/. The data
stored by the ARM Archive includes numerous parameters about radiative flux,
meteorology, water vapor and clouds.
The North Slope of Alaska/Adjacent Arctic Ocean (NSA/AAO) site is providing
data about cloud and radiative processes at high latitudes. These data are
being used to refine models and parameterizations as they relate to the Arctic.
The NSA/AAO site is centered at Barrow and extends to the south (to the
vicinity of Atqasuk), west (to the vicinity of Wainwright), and east (to
Oliktok).
Radiation data at Barrow (C1) and Atqasuk (C2) are collected using many
specialized instruments. Detailed information on each instrument is available
at http://www.arm.gov/docs/instruments.html.
The following list contains the instrumentation used and the data available for
the Barrow and Atqasuk sites.
Atmospheric Emitted Radiance Interferometer (AERI). For complete information on
the AERI, visit http://www.arm.gov/instruments. The
AERI measures the absolute infrared spectral radiance (watts per square meter
per steradian per wavenumber) of the sky directly above the instrument. The
spectral measurement range of the instrument is 500 to 3300 wavenumbers(cm-1)
or 20 to 3 microns. Spectral resolution is 1.0 cm-1. Instrument field-of-view
is 1.3 degrees. A calibrated sky radiance spectrum is produced every 10
minutes. The AERI data can be used for (1) evaluating line-by-line radiative
transport codes, (2) detecting/ quantifying cloud effects on ground-based
measurements of infrared spectral radiance, and (3) calculating vertical
atmospheric profiles of temperature and water vapor. Primary measurements are
(1) absolute infrared spectral radiance of the sky in units of watts per square
meter per steradian per wavenumber; and (2) sky brightness temperature as a
function of wavenumber in units of degrees Kelvin. Calculated quantities are
(1) variance of sky infrared spectral radiance as a function of wavenumber and
(2) vertical atmospheric profiles of temperature, potential temperature, mixing
ratio, and relative humidity.
At Barrow (C1), AERI data are available for 1998-09-22 to present.
ARM data streams are coded as follows:
nsaaerich1C1: channel 1 data
nsaaerich2C1: channel 2 data
nsaaeriengineerC1: engineering data
nsaaerisummaryC1: summary data.
Additional data streams or value added products may be added in the future.
Multi-Filter Rotating Shadowband Radiometer (MFRSR or MFR). For complete
information on the MFRSR, see
http://www.arm.gov/instruments. 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, as well as aerosol 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 (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. The primary quantities measured by the system are: (1) the direct
normal solar spectral irradiance, (2) the total horizontal solar spectral
irradiance, and (3) the diffuse horizontal solar spectral irradiance. The
measurements at each wavelength are made by a single filtered detector with a
nominal 10-nm FWHM bandwidth.
At Barrow (C1), MFR data are available for 1998-03-18 to present.
At Atqasuk (C2), MFR data are available for 2000-04-25 to present.
ARM data streams are coded as follows:
nsagndmfr: ground-oriented MFR: upwelling radiances
nsamfr10m: ground-oriented MFR: upwelling radiances at 10-m height
nsamfrsr: MFRSR: downwelling irradiances
Additional data streams or value added products may be added in the future.
The Ground Radiation (GNDRAD)
The GNRAD collection of radiometers provides
continuous measurements of broadband shortwave (solar) and longwave (infrared)
irradiances for upwelling components. For complete information on GNDRAD, see
http://www.arm.gov/instruments.
At Barrow (C1), GNRAD data are available for 1998-04-06 to present.
At Atqasuk (C2), GNRAD data are available for 2000-05-25 to present.
ARM data streams are coded as follows:
nsagndrad20s: 20-second upwelling radiation
nsagndrad60s: 60-second upwelling radiation.
Additional data streams or value added products may be added in the future.
Normal Incidence Multi-Filter Radiometer (NIMFR). For complete information on
the NIMFR, see http://www.arm.gov/instruments. The
NIMFR is a ground-based instrument that provides a time series of the shortwave
spectral direct normal irradiance. Additionally, there is a broadband silicon
detector that can crudely measure the direct normal broadband irradiance. These
irradiance measurements can be used to infer clear sky aerosol optical depth
and columnar abundances of ozone and water vapor. The NIMFR is one of a class
of instruments known as sun photometers. The primary quantities measured by the
NIMFR are direct normal spectral irradiances at six discrete wavelengths as
well as a broadband measurement from the silicon detector.
At Barrow (C1), NIMFR data are available for 1998-03-23 to present.
At Atqasuk (C2), NIMFR data are available for 2000-04-16 to present.
ARM data streams are coded as follows:
nsanimfr: direct normal irradiances.
Additional data streams or value added products may be added in the future.
The Sky Radiation (SKYRAD)
The SKYRAD collection of radiometers provides continuous measurements of
broadband shortwave (solar), longwave (infrared), and ultra violet irradiances
for downwelling components. For complete information on SKYRAD, see
http://www.arm.gov/instruments.
At Barrow (C1), SKYRAD data are available for 1998-02-14 to present.
At Atqasuk (C2), SKYRAD data are available for 1999-08-21 to present.
ARM data streams are coded as follows:
nsaskyrad20s: 20-second downwelling radiation data
nsaskyrad60: 60-second downwelling radation data
Additional data streams or value added products may be added in the future.