Realization of HHT Method to Solar Irradiance Data in MATLAB

The Hilbert-Huang transform (HHT) is a new method of analyzing non-stationary and non-linear time series data. Based on realization of HHT method in MATLAB software, we find that analytical capacity of HHT to time series in time-frequency domains stands out. The results show that (1) Solar irradiance is completely decomposed into four intrinsic mode function (IMF) components and an increasing trend by empirical mode decomposition (EMD) method, (2) it is dominated by raising-up trend for 1800-2000, (3) the Hilbert spectral analysis (HAS) method is very effective on calculation of frequencies.