Geographical variations of the influence of low-frequency variability on lower-tropospheric extreme westerly wind events

In this framework, variability is decomposed into low-frequency and synoptic components using complementary 10-day low-pass and high-pass filters, and a distinction is made between two ways that low-frequency variability influences extremes: the additive effect, which neglects the dependence of synoptic variability on the low-frequency state, and the multiplicative effect, which is due to the dependence of synoptic variability on the low-frequency state.

The influence of various factors on the relationship between low-frequency variability and extreme events is decomposed and quantified by generating a series of simple synthetic datasets based on different assumptions about low-frequency and synoptic variability and their relationship. These techniques are used to study the relationship between low-frequency variability and extreme westerly wind events in three datasets, an 1158-yr GCM simulation and two reanalysis datasets, with similar results for all three.