Figure 2
From: Calculate excess mortality during heatwaves using Hilbert-Huang transform algorithm
Significance test to separate the trend IMFs from non-trend IMFs (Brisbane data). The solid line connecting the circle points represents the white noise energy levels for each IMF; solid line segments connecting star points is the observed IMF energy level curve. Dotted line is the approximate 95% confidence band (upper limit); dashed line is the 99% confidence band (upper limit).