We're hiring a postdoc!

STRIPES Index

The STRIPES (Sensitivity to the Remote Influence of Periodic EventS) index is a metric for quantifying the strength and consistency of a region's response to a periodic event (such as the Madden-Julian Oscillation, or "MJO").

The STRIPES index offers an advantage over other types of compositing methods because it condenses, into one number, the information contained in composites of variables:

After many lags (e.g., 0 days after the event through 50 days after the event)
Throughout the life cycle of the periodic event (e.g., over phases 1 through 8 of the MJO)

The discussion below gives an overview of the calculation of the index

Here, the average winter (December-February 1948-2017) daily maximum temperature (TMAX) at a weather station in southwest Pennsylvania after various stages of the MJO life cycle is shown. For example, during winter, 40 days after MJO phase 8, the temperature at that weather station is, on average, warmer than normal.

The appearance of diagonal stripes in this type of composite plot (highlighted with arrows in the figure) is consistent with MJO propagation. The STRIPES index aims to quantify, in essence, the "stripeyness" of these types of plots.

The STRIPES index looks for the existence of diagonal stripes in composites such as the one shown above.

The STRIPES index is calculated by taking averages along the diagonals of these plots, and then calculating the variance of the result. This plot shows walks through how this is calculated for the MJO.

The variance is converted into an amplitude by taking the square root of twice its value. This number communicates the average magnitude of composites within the prominent diagonal stripes.

For more information, see:

Jenney, Andrea., D. Randall, E. Barnes: Quantifying regional sensitivities to periodic events: Application to the MJO. Journal of Geophysical Research: Atmospheres, https://doi.org/10.1029/2018JD029457.

Jenney, Andrea, K. Nardi, E. Barnes, D. Randall: The Seasonality and Regionality of MJO Impacts on North American Temperature. Geophysical Research Letters, https://doi.org/10.1029/2019GL083950

Page updated

Report abuse