Aircraft observations of the solar ultraviolet irradiance throughout the troposphere

Observations of the biological effective solar ultraviolet irradiance, made by instrumentation flown on a Falcon aircraft over the entire Greek area, from the sea up to the tropopause level, obtained in the frame of the Radiation Field in the Troposphere - Scientific Training and Access to Aircraft for Atmospheric Research Throughout Europe project, are presented to discuss among others its altitude dependence. The experimental data of the biological effective solar UV irradiance as a function of height, throughout the troposphere, showed an average increase of about 7.2 +/-1.2% km(-1), which is in close agreement with the theoretically derived one, by using an appropriate algorithm, providing the biological effective solar UV irradiance at various altitudes from the Earth's surface. This increase rate has also been compared with the burden ozone content at each height level as it was derived from ozone concentration measurements obtained by both balloon ascents and the aircraft's instrumentation. This comparison showed a strong anticorrelation (correlation coefficient r=-0.98) between the biological effective solar UV irradiance and the integrated ozone content above each height level corresponding to 0.25% increase in UV per 1 Dobson Unit (1DU=0.001 atm cm) decrease in total ozone column, approximately.