Fourier analysis of meteorological data to obtain a typical annual time function

A method of calculation has been developed for obtaining a typical annual time function, by means of Fourier analysis, that is applicable to meteorological parameters which show significant frequencies and have sufficient climatological series. Applied with excellent results to annual series of daily data on global solar irradiation (9 yr) and average, maximum and minimum air temperatures (10 yr) of Barcelona city, with the observation that only the annual harmonic contributes in any significant way.