UV‐B irradiance at Madrid during 1996, 1997, and 1998

During 1996, 1997, and 1998, several total ozone depletion events were detected over Madrid (40°N, 3°W) in late spring and in winter. A broadband interferential filter instrument (UV‐300) centered at 298 nm was used to monitor the solar UV‐B irradiance on the ground, registering UV‐B levels as high as 17.1 μW/cm2 (May 2, 1997, solar zenith angle SZA = 35°, O3 = 268 Dobson units). The data obtained have been compared to that measured with two commercial biometers (PMA2102 and Solar Light 501A), showing that the evolution of UV‐B due to total ozone changes are better followed with broadband instruments with effective windows centered at lower wavelength than with instruments responding to the erythemal action spectra. The development of simple, portable, and reliable instruments for the analysis of solar UV‐B phenomena at the high‐energy side of that band is advocated.