USE AND EVALUATION OF BIOLOGICAL SPECTRAL UV WEIGHTING FUNCTIONS FOR THE OZONE REDUCTION ISSUE - Environmental UV Radiation: Impact on Ecosystems and Human Health and Predictive Models - page 68

USE AND EVALUATION OF BIOLOGICAL SPECTRAL UV WEIGHTING
FUNCTIONS FOR THE OZONE REDUCTION ISSUE
MARTYN M. CALDWELL AND STEPHAN D. FLINT
Utah State University
Logan, Utah 84322-5230 USA
1. Introduction
1.1. ROLES OF BIOLOGICAL SPECTRAL WEIGHTING FUNCTIONS IN THE
OZONE REDUCTION ISSUE
Biological spectral weighting functions (BSWF) are used in evaluating the stratospheric
ozone problem in several ways. Best known is their use as the basis for radiation
amplification factors (RAF) that predict the relative increment in "biologically
effective'' UV radiation for each step of ozone depletion [1]. They are used to evaluate
latitudinal gradients of solar UV-B [2] and to calculate how much supplemental UV to
supply in experiments with UV-B-emitting lamp systems [3]. Outdoor experiments with
filters intended to reduce natural solar UV have also been conducted, though they are
less common than the UV-supplementation experiments. Thus, for assessing the
importance of ozone column reduction, the BSWF's play several critical roles.
1.2. WAVELENGTH SENSITIVITY OF BSWF'S
In the solar UV spectrum, the absorption coefficient of ozone plays a decisive role in
the wavelength composition of sunlight. Other atmospheric agents of radiation
attenuation are important, but they have much less wavelength specificity compared
with the absorption by ozone (Figure 1).
Because ozone absorption is so wavelength specific, the ground-level solar
spectrum drops by orders of magnitude in a mere 30 nm of wavelength. But, often
action spectra, and therefore BSWF, can also increase by orders of magnitude in
the same general wavelength range as the solar UV spectral irradiance is decreasing
(Figure 2).