1. Calibration of a Yankee Environmental Systems
UltraViolet Rotating Shadow Band
Radiometer at Mauna Loa Hawaii
Presented at the 10th International Pyrheliometer Intercomparison
in Davos, Switzerland September 26 to October ,
by Fred Denn

2. Why is UV important?
Health effects
Agriculture
Energy deposition in the atmosphere
How to measure?
Satellites
Ground stations

3. Satellite derived top of atmosphere spectral measurements
are used to determine global and temporal UV surface
irradiance and atmospheric energy deposition.
Surface measurements are made, to verify the results of
the atmospheric radiative transport models, requiring
well calibrated surface instrumentation.
A method of calibrating UV-MFRSRs using satellite
derived UV spectrum is presented.

4. The UV-MFRSR is located at the Mauna Loa Observatory,
Hawaii for a period of time each year because of the
exceptionally clear and stable atmosphere. Langley
analysis are performed, on the morning data, to determine
top of atmosphere values.
Mauna Loa observatory Hawaii

5. Langley plots were used to select morning data periods
used in later analysis.
To be considered a good the standard deviation of the residuals
must me less than 0.006

6. The daily values were plotted for the entire time period,
means and standard deviations were determined. These means
will be compared to values derived using the MFRSR spectral
response and the SOlar Radiation and Climate Experiment
(SORCE) satellite measured extraterrestrial UV spectrum.

7. Overview of Method Use a spectral line lamp to verify functionality
of a monochromator.
Determine the normalized functional response
of the UV-MFRSR head.
Preform a numerical integration using the UV-MFRSR
spectral response function and a satellite derived UV
spectrum.

8. Top of Atmosphere MFRSR Measured Values and the Values
Determined From the MFRSR Spectral Response Function
and the SORCE Spectrum are Compared.

9. TOA values are determined, and scale factors used to
adjust the MFRSR derived values to more true values.
Normalized to 1 au
Wavelen, nm Scale factor ±U95% TOA, W/m ±U95%

10. Verification of New Values
Corrected
Wave len SIM derived TOA UVMFR-7 TOA Difference
nm W/m W/m W/m2

11. Conclusion Manufactures calibration can be improved
by applying Langley analysis to the output
values supplied by there software.

12. Acknowledgments
NASA Langley
PMOD
U.S. Coast Guard