RELATIONSHIP BETWEEN DIURNAL VARIABILITY AND ANNUAL CYCLE OF METEOROLOGICAL VARIABLES

V. N. Ivanov and A. V. Khokhlova

Diurnal harmonics of 6–24 hours are studied using a spectral analysis of 44-year<%0> time series of meteorological variables in the lowest atmospheric layer at several stations of the European Russia with a time step of three hours. Spectra of surface temperature, pressure, absolute humidity, wind velocity components, and low and total clouds are shown to have both a diurnal harmonic and its harmonics equal to 12, 8, and 6 hours. There are side maximums some minutes apart from the primary ones (24.066 and 23.934 h for a diurnal harmonic) and some additional secondary maximums in the spectrum. The number and magnitude of these maximums are different for various parameters, harmonics, and stations, but they are always in the same frequency length apart from the primary maximums. It is shown that such a splitting of spectral lines is determined by an amplitude modulation of diurnal cycle of meteorological variables by a low frequency annual cycle. A multiplicative model based on two fundamental frequencies (diurnal and annual variations) is suggested. The model describes the average regularities and a spectral composition of meteorological variables in the frequency band indicated.