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.