Photolysis rate coefficients calculations from broadband UV-B irradiance: model-measurement interaction

Broadband UV-B irradiance measurements (YES UVB-1) from a 4-year campaign in Córdoba City (31° 24′ S, 64° 11′ W, 454 m a.s.l.) and the TUV 4.1 model were used to apply a new approach (exp-mod) to convert broadband irradiance measurements at surface under clear sky conditions to actinic flux and then to J-values. The structure of the model was used to split each measurement into its diffuse and direct component and, in turn, in wavelengths. The results for the daily variation of JO3 shows an agreement better than 5% for solar zenith angles (SZA) up to 65° and better than 10% up to 70° compared against an 8-stream discrete ordinate method. The annual variation of JO3 for clear sky days at solar noon shows a general agreement better than 10%. The effects of the natural variation of ozone column and the Córdoba meteorology on this agreement are analyzed. Empirical relations between experimental measurements and J-values calculated with a 2-stream δ-Eddington method are also presented.