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

During 1996, 1997, and 1998, several total ozone depletion events were dete cted over Madrid (40 degrees N, 3 degrees W) in late spring and in winter. A broadband interferential filter instrument (UV-300) centered at 298 nm wa s used to monitor the solar UV-B irradiance on the ground, registering UV-B levels as high as 17.1 mu W/cm(2) (May 2, 1997, solar zenith angle SZA = 3 5 degrees, O-3 = 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 lowe r wavelength than with instruments responding to the erythemal action spect ra. The development of simple, portable, and reliable instruments for the a nalysis of solar UV-B phenomena at the high-energy side of that band is adv ocated.