SOLAR RADIATION AND ITS MEASUREMENT - Environmental UV Radiation: Impact on Ecosystems and Human Health and Predictive Models - page 23

SOLAR RADIATION AND ITS MEASUREMENT

HARALD K. SEIDLITZ AND ANDREAS KRINS
GSF-Forschungszentrum für Umwelt und Gesundheit
85764 Neuherberg, Germany

1. Introduction

Solar radiation reaching the Earth's surface is a key factor for the development
of life. It is characterised by both the intensity and the spectral composition. Its
spectrum reaches from approximately 290 nm to 3000 nm. A considerable amount of
the energy is contained in the ultraviolet band of which especially the short wave part
below 315 nm is considered to be harmful for men, animals and plants. The range
between 280 and 315 nm is designated as UV-B radiation, the range between 315 and
400 nm as UV-A radiation (Fig. 1). The exact definitions of radiation quantities is
presented in the another contribution in this volume 1 .

UV Light (visible) Infrared

200 300 400 500 600 700 800 900

Wavelength (nm) O 280 315

10 8 6 5 4 3 2

10 -19

Photon Energy, E (J)

Figure 1. Schematic presentation of the electromagnetic spectrum.

The quantification of the amount and the quality of UV radiation and light
reaching the Earth's surface or a given biological system under consideration is of
major importance in basic biological research, especially for the assessment of the
impact of UV on human health and ecosystems. Especially the study of the complex -
coupled - pattern of plants' responses to light and UV radiation, the understanding of
the regulatory mechanisms by which plants can adapt to changing environmental
conditions call for reliable light and UV measurements.