TITLE: INDOEX: Aircraft C-130 Radiation Actinic Flux Spectroradiometer (Campos)
AUTHOR(S):
Teresa L Campos and Richard E Shetter
NCAR Atmospheric Chemistry Division
PO Box 3000
Boulder, CO 80307-3000
Phone: 303-497-1879
Fax: 303-497-1411
campos@acd.ucar.edu
shetter@acd.ucar.edu
1.0 - 3.0 DATA SET SUMMARY AND INSTRUMENT DESCRIPTION:
The NCAR C-130 platform measured spectrally resolved solar flux. Two
spectroradiometers were integrated in zenith and nadir locations to provide
upwelling, downwelling and total actinic flux spectra. Photographs of the
zenith and nadir spectroradiometer installations are shown in Figures 1 and 2,
respectively. The collection optics and shadow rings were configured to match
the heights of other radiometric instruments installed on the aircraft. Due
to a shortage of seats available on research flights, the instrument was
designed to operate unattended once power had been supplied to the instrument.
Dr. Campos also operated the instruments on ferry flights from Boulder to Male;
these data are available upon request to the principle investigators.
The spectroradiometric method referenced in Shetter and Muller [1999] was
modified to provide actinic flux spectra over the extended wavelength range of
300 to 920 nm with a 0.25-Hz time response, employing a diode array spectrometer.
The hemispherical quartz collection optics were implemented as described in
Shetter and Muller. Figure 3 illustrates the typical angular response
over 2(-steradian of each hemispheric collection optic. Data coverage during
the INDOEX intensive was better than 98% for C-130 research flights (16
February, 1999 through 25 March, 1999).
Figure 1 (http://www.joss.ucar.edu/data/indoex/docs/c130.afs.fig1.gif)
Figure 2 (http://www.joss.ucar.edu/data/indoex/docs/c130.afs.fig2.gif)
Figure 3 (http://www.joss.ucar.edu/data/indoex/docs/c130.afs.fig3.gif)
The performance specifications were established to enable acquisition of actinic
flux spectra covering the range from 300 to 920 nm with a resolution of 3 nm
(FWHM). The wavelength-dependent instrument response function was determined
approximately to have the shape of a smoothed triangle, so the detection limit
for actinic flux measurement was approximately 0.5 (W/cm2-nm at 300 nm and
approximately 0.1 at 600 nm.
4.0 DATA FORMAT:
Data file structure: space delimited ASCII
File naming convention: c130.afs.yymmdd_sum_tot.flx
Header: No Header
Equivalent Header Information:
PI/DATA CONTACT= Campos, Teresa (NCAR), Shetter, Rick (NCAR)
PLATFORM/SITE = C130
INSTRUMENT = C-130 total actinic flux spectra
DATA VERSION = 1.0 (25 March 2000), FINAL
REMARKS = National Center for Atmospheric Research, INDOEX
REMARKS = Data point Time provided in UTC in hh:mm:ss format
REMARKS = Missing data = -9999; Bad data = -9999
File Parameters: UTC (time, hh:mm:ss)
Wavelength (nm)
Actinic Flux (photons/cm2/s-1/nm)
Version number: 1.00, 25 March 2000, FINAL DATA
Missing and Bad Data Flag: -9999.
REFERENCES
B Shetter, Richard E and Martin Muller, 1999, "Photolysis frequency
measurements using actinic flux spectroradiometry during the PEM-Tropics
mission: Instrumentation description and some results," Journal of
Geophysical Research, 104(5), 5647.