Composites are made using data from the 1979-2008 period. A pentad is included in the composite if the magnitude of
the RMM index is greater than 1.0 standard deviation. They are not, however, dependent on propagation of an MJO event.
For masked composites, significance is assessed using a simple student's t-test, and the areas not significant at the
95% level are masked out.
For more information on the methodology and background, see Baxter et al. (2014).
Stephen Baxter, Scott Weaver, Jon Gottschalck, and Yan Xue, 2014: Pentad Evolution of Wintertime Impacts of the
Madden-Julian Oscillation over the Contiguous United States. J. Climate, 27, 7356-7367.