Actinic flux and O1D photolysis frequencies retrieved from spectral measurements of irradiance at Thessaloniki, Greece

[摘要] The results of two methods retrieving actinic flux and ozone photolysisfrequencies (JO¹D), from measurements of irradiance with a Brewer MKIIIspectroradiometer are investigated in this paper. The first method usesactinic flux retrieved from irradiance measurements by the use of knownformulas while the second is an empirical method converting irradiance toJO¹D through polynomials extracted from a study of synchronous actinicflux and irradiance measurements. When examining the actinic fluxes derivedfrom the first method to those measured by an actinic flux spectrometer dataagree within ±10% for solar zenith angles lower than 75° forthe UV-B and the UV-A wavelength band. Also, the actinic to globalirradiance ratio derived, deviates within ±6% for solar zenithangles lower than 70° compared with cloudless sky calculations of theTUV model. For both cases the deviations are in the order of the magnitudeof the measurement or model uncertainties. Values of JO¹D calculatedby the second method show a mean ratio of 0.99±0.10 (1σ) and0.98±0.06 for all data and for cloudless skies respectively whencompared with values of JO¹D derived by a Bentham actinic fluxspectroradiometer. Finally, the agreement of the two methods is within±5% comparing two years' data of JO¹D retrieved from irradiancemeasurements at Thessaloniki, Greece. The use of such methods on extensivedata sets of global irradiance can provide JO¹D values with acceptableuncertainty, a parameter of particular importance for chemical processstudies.

[学科分类] 大气科学