Determining the phases of the semidiurnal temperature and pressure oscillations by the cross-correlation equilibrium method

In the processing of temperature and atmospheric pressure data observed in an underground laboratory, the cross-correlation equilibrium method is proposed for determining the phase of a signal with a particular frequency. This method effectively suppresses the influence of white noise and reduces the phase errors derived from higher order harmonics and any direct current component in the experimental signal. The upper limit of phase error due to the other frequencies in the experimental data is estimated. Theoretical analysis and the result of computational simulation show that the signal-to-noise ratio of the phase determined is improved significantly.