Organization(s):

National Oceanic and Atmospheric Administration (NOAA), Earth System Research Laboratory (ESRL)

Network For the Detection of Atmospheric Composition Change (NDACC)

National Institute of Water and Atmospheric Research (NIWA)

What does this program measure?

Spectrally resolved solar Ultraviolet (UV) irradiance reaching the Earth’s surface. Units: Watts per square meter per nanometer. Biologically weighted irradiances are in units of Watts per square meter.

How does this program work?

The UV spectroradiometer uses a double monochromator grating spectrometer to measure the UV spectrum between 285 nm and 450 nm with a resolution of 0.8 nm. The measurement thus includes the UVB and UVA regions, and some of the visible spectrum. The system is controlled by computer. Measurements are taken at 5 degree solar zenith angle steps throughout the day (for sza <=95 degrees), except for a 2 hour period around local solar noon when spectra are taken at 15 minute intervals. Spectra are also taken at midnight. The instrument is calibrated weekly using a mercury lamp and a 45-Watt standard lamp. An absolute calibration is performed several times per year using a 1000-Watt standard lamp powered by a precision current source.

Why is this research important?

To measure a climatology of UV radiation in an extreme environment, and to understand the causes of its variability and its sensitivity to climate change factors such as ozone depletion and global warming.

Are there any trends in the data?

No long-term trends have been detected. However, there are large seasonal and year to year variabilities.

How does this program fit into the big picture?

What is it's role in global climate change?

Changes in UV radiation are critical to our understanding of the effects of ozone depletion. In addition, UV radiation at the surface is influenced by clouds and aerosols, both of which are subject to modification due to anthropogenic influences. By carrying out measurements in pristine locations over long periods, the importance of these changes can be assessed. This is one of the aims of the Network for the Detection of Atmospheric Composition Change (NDACC). The Mauna Loa Observatory is the prime low-latitude site in this network.

Comments and References

This has been a very successful program. In the initial stages Dr Barry Bodhaine was the NOAA primary investigator. Numerous publications from this work have advanced our understanding of the relative importance of factors that influence UV radiation. Because of its high altitude and low latitude, the UV intensities measured at this site are among the highest recorded anywhere in the world. It is not uncommon to experience UV Index values exceeding 20 (UVI values greater than 10 are considered “extreme” at most mid latitude sites). The instrumentation and calibration procedures are continuously being improved.

• Bodhaine, B. A., E. G. Dutton, D. J. Hofmann, R. L. McKenzie, and P. V. Johnston, Spectral UV measurements at Mauna Loa: July 1995-July 1996, J. Geophys. Res., 102, 19,265-19,273, 1997.
• Bodhaine, B. A., E. G. Dutton, R. L. McKenzie, and P. V. Johnston, Calibrating broadband UV instruments: ozone and solar zenith angle dependence, J. Atmos. Oceanic Technol., 15, 916-926, 1998.
• Bodhaine, B. A., E. G. Dutton, R. L. McKenzie, and P. V. Johnston, UV spectroradiometer and ozone measurements at Mauna Loa, Hawaii, and Boulder, Colorado, poster? presented at American Geophysical Union Fall Meeting, San Francisco, December, 1998.
• Bodhaine, B. A., E. G. Dutton, R. L. McKenzie, and P. V. Johnston, UV spectroradiometer and ozone measurements at Mauna Loa, Hawaii, and Boulder, Colorado, poster presented at Annual meeting of NOAA/CMDL, NOAA, Boulder Co, 12-13 May, 1999.
• Bodhaine, B. A., D. J. Hofmann, E. G. Dutton, R. L. McKenzie, P. V. Johnston, M. Kotkamp, R. C. Schnell, J. E. Barnes, and S. C. Ryan, Ultraviolet spectroradiometer measurements at Mauna Loa observatory, in IRS '96: Current Problems in Atmospheric Radiation, University of Alaska, Fairbanks, Alaska, edited by W. L. Smith and K. Stamnes, pp. 841-844, Deepak, Hampton, Va, 1997.
• Bodhaine, B. A., D. J. Hofmann, E. G. Dutton, S. J. Oltmans, R. L. McKenzie, and P. V. Johnston, Ultraviolet Radiation and Total Ozone Correlations at Mauna Loa Observatory, and Boulder, Colorado, poster presented at Network for the Detection of Stratospheric Change (NDSC) 2001 Symposium "Celebrating 10 Years of Atmospheric Research", NDSC, Palais des Congrès "Le Palatium", Arcachon, France, 24-27 September, 2001.
• Bodhaine, B. A., R. L. McKenzie, P. V. Johnston, D. J. Hofmann, E. G. Dutton, R. C. Schnell, J. E. Barnes, S. C. Ryan, and M. Kotkamp, New ultraviolet spectroradiometer measurements at Mauna Loa observatory, Geophys. Res. Lett., 23, 2121-2124, 1996.
• McKenzie, R. L., Spectrally-resolved UV Radiation Measurements at Lauder New Zealand, Mauna Loa Observatory Hawaii, and other sites., presented at Seminar, NOAA/CMDL, Boulder, Co., 21 may 1998, 1998.
• McKenzie, R. L., P. V. Johnston, G. E. Bodeker, M. Kotkamp, B. A. Bodhaine, D. J. Hofmann, E. G. Dutton, R. C. Schnell, J. E. Barnes, and S. C. Ryan, UV spectral irradiance comparison and contrast between Mauna Loa observatory, Hawaii, and Lauder, New Zealand, in Proceedings of the XVIII Quadrennial Ozone Symposium, L'Aquila, Italy, 2, edited by R. D. Bojkov and G. Visconti, pp. 857-860, Parco Scientifico e Technologico d'Abruzzio, L'Aquila, Italy, 1998.
• McKenzie, R. L., P. V. Johnston, M. Kotkamp, D. Smale, and B. A. Bodhaine, Effects of Altitude on UV Spectral Irradiance deduced from measurements at Lauder, New Zealand and at Mauna Loa Observatory, Hawaii, in Quadrennial Ozone Symposium, Sapporo, Japan, edited by R. D. Bojkov and K. Shibasaki, pp. 277-278, EORC/NASDA, Tokyo, 2000.
• McKenzie, R. L., P. V. Johnston, and G. Seckmeyer, UV spectro-radiometry in the network for the detection of stratospheric change (NDSC), in Solar Ultraviolet Radiation. Modelling, Measurements and Effects, Halkidiki, Greece, 1.52, edited by C. S. Zerefos and A. F. Bais, pp. 279-287, Springer-Verlag, Berlin, 1997.
• McKenzie, R. L., P. V. Johnston, D. Smale, B. Bodhaine, and S. Madronich, Altitude effects on UV spectral irradiance deduced from measurements at Lauder, New Zealand and at Mauna Loa Observatory, Hawaii, J. Geophys. Res., 106, 22845-22860, 2001.