The features of the CLEAN algorithm for Fourier analysis of time series with data separated by long pauses are analyzed in detail. Estimates are obtained for the limits of variability of the parameters of harmonic components that can be determined on a specified time grid. This analysis are used to search for harmonic components in the spectral line profile variations of the star λ Ori A (O8III) obtained in 2001 with the 1 m telescope at the Special Astrophysical Observatory of the Russian Academy of Sciences.