1.
Introduction
Solar radiation is an important natural
factor because it forms the Earth’s climate and has a significant influence
on the environment. The ultraviolet part of the solar spectrum (UV) plays
an important role in many processes in the biosphere. It has several beneficial
effects but it may also be very harmful if UV exceeds ”safe” limits. If
the amount of UV radiation is sufficiently high the self-protection ability
of some biological species is exhausted and the subject may be severely
damaged. This also concerns the human organism, in particular the skin
and the eyes. To avoid damage from high UV exposures, both acute and chronic,
people should limit their exposure to solar radiation by using protective
measures.
The diurnal and annual variability of solar
UV radiation reaching the ground is governed by astronomical and geographical
parameters as well as by the atmospheric conditions. Since human activities
affect the atmosphere, such as polluting the air and influencing the ozone
layer, they also affect the UV radiation reaching the ground. As a consequence,
solar UV radiation is a highly variable environmental parameter that differs
widely in time and space. The need to reach the public with simple-to-understand
information about UV and its possible detrimental effects led scientists
to define a parameter that can be used as an indicator of the UV exposures.
This parameter is called the UV Index. It is related to the well known
erythemal effects of solar UV radiation on human skin and it has been defined
and standardised under the umbrella of several international institutions
such as WMO, WHO, UNEP and ICNIRP (see Appendix E).
The UV Index (UVI) is now widely used in
many operational weather reports and forecasts. In Europe, for example,
there are more than a dozen forecasting centres that release estimated
UVI values for countries or regional areas. Different methods are used
to predict the UVI and all kinds of information systems and presentations
are seen. To co-ordinate these activities and to improve their scientific
background an international research project was established under the
program ”Cooperation in Science and Technology” (COST) of the European
Commission. The project titled COST-713 action (UV-B Forecasting) was initiated
in 1996. The following European countries participated: Austria, Belgium,
Czech Republic, Denmark, Finland, France, Germany, Greece, Italy, Poland,
Portugal, Spain and Switzerland. A list of the participating institutions
is given in Appendix A.
The development of efficient methods for
dissemination of the UVI forecasts and the improvement of how they are
interpreted by the public were key tasks for COST-713. This booklet is
one product of the action and is mostly intended for users coming from
different professional communities who can assist in a wider use of the
UVI. It may also be useful to users who want to know about the details
of the physical and biological background.
It is expected that the readers will use
this information not only in their professional activities but also for
communication to the public. The international and local institutions listed
in the booklet (Appendix B) may serve as reference centres for further
information and assistance.
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