We investigate in this paper the dominant intraseasonal signals in both convection and circulation data using the nonlinear Laplacian spectral analysis (NLSA) method. Three Madden-Julian oscillation (MJO) indices are constructed based on temporal modes extracted from pure cloudiness, lowerand upper-level zonal wind anomalies. All three indices reveal strong intermittency and capture well – thro...

The streamfunction and velocity potential variances associated with the Madden–Julian oscillation are explained substantially by their zonal wavenumber-1 components, which are used to measure quantitatively the phase relationship between the two variables. There exists a quarter-cycle phase difference between them. A simplified streamfunction budget equation was used to demonstrate analytically...