NO2 and HCHO photolysis frequencies from irradiance measurements in Thessaloniki, Greece

[摘要] An empirical approach for the retrieval of nitrogen dioxide (NO₂) andformaldehyde (HCHO) photolysis frequencies from measurements of globalirradiance is presented in this work. Four months of synchronousmeasurements of actinic flux and global irradiance performed inThessaloniki, Greece by a Bentham spectroradiometer were used to extractpolynomials for the conversion of global irradiance to photolysisfrequencies [J(NO₂) and J(HCHO)]. The comparison of these photolysisfrequency values to the corresponding values calculated by spectral actinicflux measurements, showed a ratio very close to unity for all J's with astandard deviation of 12% (2σ) for J(NO₂) and 6%(2σ) for J(HCHO). Additional sets of polynomials were also extractedto allow determination of J(NO₂) by spectroradiometers with lower upperwavelength limits such as single and double Brewer spectroradiometers withinacceptable uncertainty (corresponding ratio was 1 and standard deviation was12% (2σ) for the method that can be used with double Brewers and20% for the method that can be used for single Brewers). The validity ofthe method under different atmospheric conditions was also examined byapplying the polynomials to another set of actinic flux and globalirradiance measurements performed in May 2004, in Buchhofen, Germany. Inthis case, comparing J values extracted from the polynomials to thosecalculated from actinic flux, showed equivalent results, demonstrating thatthe method can also be applied to other measurement sites.

[学科分类] 大气科学