Bispectral analysis of the long‐term recording of surface pressure at Jakarta

Abstract

The long‐term series of surface pressure at Jakarta (6 S, 107 E) from 1842 to 2000 are analyzed for nonlinear three‐wave interaction. In the tropics, the variations of surface pressure are mainly caused by variations of the water vapor pressure. Jakarta is located in the strongest zone of water vapor convection of the Earth, and the pressure variations at Jakarta essentially influence or drive the circulation of the Earth's atmosphere. The bispectrum evaluates the phase relationships and the magnitudes of oscillation triads having the frequencies f1, f2, and f3 = f1 + f2. Analysis of the bispectrum from intraseasonal to decadal timescales quantifies the degree of nonlinearity in the troposphere and reveals the dominant oscillation triads. The bispectrum also informs about the energy and impulse transfer from low to high frequencies and vice versa. We find following main results for the Jakarta series: (1) a strong annual oscillation and strong harmonics up to the fourth order and higher, (2) strong interactions between the annual oscillation (AO) and the biennial oscillation (BO) and several components of the quasi‐biennial oscillation (QBO with periods at 2.79, 2.39, 1.72, 1.56‐year), (3) mixing processes between the annual harmonics and the interannual and decadal oscillations (10 to 40‐year) are obvious in the bispectrum, FFT‐spectrum, and in the temporal evolution of the amplitudes (derived from the bandpass‐filtered time series), and (4) a close relationship is found between the amplitudes of the semi‐annual oscillation and the quasi 4‐year oscillation (nonlinear interaction 2 cycles/a + 0.25 cycles/a = 2.25 cycles/a). The bispectral analysis of the Jakarta series gives us a detailed insight into the self‐organization of the atmospheric oscillations by nonlinear three‐wave interaction and permits the development of a strategy for improved detection, modeling, and forecasting of atmospheric variability.