STRIPES: A New Index for Quantifying Regional Sensitivities to Remote Heating

The weather prediction community has been making strides in applying the predictive power of periodic weather phenomena, such as the Madden-Julian Oscillation (MJO), to skillful forecasts. However, it is understood that regional variations in mid- and high-latitude sensitivity to the MJO exist. For example, the strength and location of extreme temperature and precipitation phenomena, as well as the skill of their prediction, are shown to vary with the MJO. Furthermore, verifications of both statistical and numerical forecast models trained or conditioned on the MJO reveal regional variations in model skill, hinting at regional variations in MJO teleconnection strength. We have developed an index to concisely quantify these regional Sensitivities to the Remote Influence of Periodic EventS (STRIPES). The STRIPES index compiles the information obtained through composite analysis of observed variables after a periodic event, such as the MJO, into a single number, which includes information about the entire life cycle of the event and for a range of lags with respect to each stage of the event. The STRIPES index quantifies the strength and consistency of a region's response to the remote periodic event. Because the index can be computed for a single point, it can be plotted on a map to show regional variations, and thus offers an advantage over previously used compositing techniques. Additionally, it can be applied to diverse weather variables, seasons, and other periodic weather phenomena, such as the Boreal Summer Intraseasonal Oscillation. Utility of the STRIPES index is demonstrated by applying it to a subset of the SubX database and comparing it to a similar analysis of observed weather.