Wavenumber-Frequency Spectra of Temperature in the Free Atmosphere

Abstract

An analysis of the wavenumber-frequency spectra of temperature in the free atmosphere is made. It is found that a striking similarity exists between the spectrum of temperature and that of the large-scale wind velocity in the free atmosphere. The wavenumber-frequency spectrum of temperature shows a preferred spectral domain of wave activities, oriented primarily from a region of low wavenumbers and low frequencies to a region of high wavenumbers and negative frequencies assigned to waves moving from west to east. In the high-wavenumber range, the wavenumber spectrum of temperature is approximately proportional to the ?3 power of the wavenumber. In the high-frequency range, the frequency spectrum of temperature is approximately proportional to the ?1 power of the frequency. These indicate that the structure of the temperature field in the free atmosphere is essentially affected by the large-scale two-dimensional turbulent motion. It is also found that most of the sensible heat is associated with the stationary zonal mean motion, and that there is more sensible heat associated with nonstationary waves than with stationary waves in the atmosphere.