For climatological studies it is most important to have data from long time series observations. Typical UV measurement series are not longer then 15 years. The UV reconstruction algorithms pretend to enhance UV data series, using the solar radiation measurements, available even since 1950. In the presented method, the UV (erythemal) reconstruction algorithm is based on temporal variability analysis. The proposed procedure with Fast Fourier Transform (FFT) computes power spectrum of the global irradiance (GR) transmission for all or for the selected part of the diurnal cycle. The similar GR transmission power spectra are found from the available series of data. It has been shown, that for the data with similar power spectra in GR transmittance, the power spectra in the UV transmittance are as well similar. So, it is possible to calculate the all-sky UV irradiance, using the UV transmittance and the radiation transfer model for clear-sky. This algorithm is particularly useful to estimate the effect of clouds on the downwelling shortwave irradiance (without direct cloud observations). The algorithm can be applied for UV reconstruction, using information on total solar irradiance, total ozone and aerosols. As the second approach the wavelet method has been applied. The Streamer and Fastran radiation transfer models have been used for testing the proposed UV reconstruction algorithms. The testing has been performed on available data from Arosa site, for year 2002, within COST 726 Action.
The objectives of the COST action 726 are to establish long-term changes of UV-radiation in the past, which can only be derived by modelling with good and available proxy data. To find the best available models and input data, 16 models have been tested by modelling daily doses for two years of data measured at four stations distributed over Europe. The modelled data have been compared with the measured data, using different statistical methods. Models that use Cloud Modification Factors for the UV spectral range, derived from co-located measured global irradiance, give the best results.
The paper presents the results of the work aimed at the application of visibility (meteorological visual range) data for UV modeling in Poland for summer season. In the first step, the meteorological visibility data were processed in order to obtain the monthly mean visibility maps that correspond to aerosols distribution over Poland. The usefulness of such maps was then validated through the comparison with AERONET data as well as the results of the UV radiation transfer model calculations. The comparison with AERONET data shows that monthly mean values of aerosol optical depth, calculated from visibility data, are in a good agreement with ground measurements for most summer months. The monthly mean visibility maps were then used in the UV radiation transfer modeling. The results of the comparative analysis performed for three Polish stations: Leba, Legionowo, Zakopane are presented and discussed. It has been shown that use of monthly mean visibility values leads to an improvement in the UV calculations quality as opposed to the calculations done with a priori assumed aerosol conditions.