New observations of ultraviolet radiation and column ozone from Socorro, New Mexico

Measurements of surface ultraviolet irradiances are presented for the perio d of June 1997 to December 1998 from Socorro, NM (34 degrees N, 107 degrees W). The observations are used with results of radiative transfer calculati ons to retrieve total column ozone. Mean differences between Socorro daily ozone measurements and Earth Probe TOMS satellite data are -1.8 DU and 0.6 DU for 1997 and 1998, respectively. Unusually low ozone was observed in lat e November and December of 1998, with levels near or below the lowest ozone in the 17-year Nimbus-7 and Earth Probe TOMS record for this location. The clear-sky correlation between the UV Index at 60 degrees solar zenith angl e and total ozone is well described by a power law, with an exponent (Radia tion Amplification Factor) of 0.97+/-0.16. One exception occurred during a 10-day period in December 1997 and January 1998 in the aftermath of a heavy snow storm, when the UV Index exhibited clear-sky enhancements of up to 30 %. Increases in downwelling ultraviolet radiation were related to a higher effective surface albedo with maximum estimated values between 0.7 to 0.9.