Research ArticleATMOSPHERIC SCIENCE

Diversity of the Madden-Julian Oscillation

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Science Advances  31 Jul 2019:
Vol. 5, no. 7, eaax0220
DOI: 10.1126/sciadv.aax0220

Figures

  • Fig. 1 Example of diversified propagation patterns of the MJO.

    Hovmöller diagram of intraseasonal OLR averaged between 10°S and 10°N for the 1983–1984 boreal winter and the 1996–1997 boreal winter is shown. The blue contours indicate −10 W m−2 contours. The thick horizontal dash lines indicate the reference dates for the selected events. The clustered events are labeled. The methods for data filtering, selection of the MJO events, and the MJO classification are described in the Material and Methods section. A zonal three-point running mean was applied to the Hovmöller diagram to remove small-scale noises.

  • Fig. 2 Four types of MJO propagation patterns along the equator.

    Composited longitude-time diagram of intraseasonal OLR anomalies (contour, W m−2) averaged between 10°S and 10°N during boreal winter from November to April for (A) standing, (B) jumping, (C) slow propagation, and (D) fast propagation clusters. The dashed black contour is the −5 W/m2 contour. The shading shows significant signals at 95% confidence level. The black solid lines in (C to D) indicate phase propagation, which is obtained by a least-square fit of the minimum OLR. The phase speed is shown on the top right corner of the panels.

  • Fig. 3 Equatorial vertical structures of the four types of MJO.

    Composited equatorial (averaged between 10°S and 10°N) vertical structure of circulation (vectors), equivalent potential temperature (EPT, contours in units of K), and precipitation heating (color shading, in units of 1 × 10−2 J kg−1 s−1) for (A) standing, (B) jumping, (C) slow propagation, and (D) fast propagation clusters. Stipples denote where the EPT anomalies are significant at 95% confidence level. The precipitation heating anomalies are only shown for those significant at 95% confidence level. Vectors represent the zonal and vertical velocity (units are m/s for zonal wind and 0.01 Pa s−1 for vertical pressure velocity). Only wind vectors that are significant at 95% confidence level are shown. The vertical lines indicate 100°E. The blue circle indicates the location of maximum upward motion.

  • Fig. 4 Horizontal structures of the four types of MJO.

    Composited 700-hPa winds (vector, m/s) for (A) standing, (B) jumping, (C) slow propagation, and (D) fast propagation clusters. Only those winds that are statistically significant at the 95% confidence level are plotted. The shading indicates the convective instability index measured by the EPT difference between 850 and 400 hPa (EPT 850 minus EPT 400). The stipples indicate regions where the convective instability indices are significant at 95% confidence level. A nine-point smooth is applied to the convective index field. Blue circles mark the MJO convective center on the equator.

  • Fig. 5 Background SST anomalies associated with the four MJO clusters.

    The background SST anomalies are obtained by compositing the 3-month average of monthly SST anomalies (derived from climatological monthly mean) for each MJO cluster, with the central month being the month that contains day 0 of an MJO event.

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