Abstract
Based on the daily sunspot number (SN) data (1954–2011) from the Purple Mountain Observatory, the extreme value theory (EVT) is employed for the research of the long-term solar activity. It is the first time that the EVT is applied on the Chinese SN. Two methods are used for the research of the extreme events with EVT. One method is the block maxima (BM) approach, which picks the maximum SN value of each block. Another one is the peaks-over-threshold (POT) approach. After a declustering process, a threshold value (here it is 300) is set to pick the extreme values. The negative shape parameters are obtained by the two methods, respectively, indicating that there is an upper bound for the extreme SN value. Only one value of the N-year return level (RL) is estimated: N = 19 years. For N = 19 years, the RL values of SN obtained by two methods are similar with each other. The RL values are found to be 420 for the POT method and the BM method. Here, the trend of 25th solar cycle is predicted to be stronger, indicating that the length of meridional forms of atmospheric circulation will be increased.
Highlights
Acero et al (2017) [21] applied the extreme value theory (EVT) on the new version of the sunspot number (SN) index at daily, monthly, and yearly timescales, and the results showed that the return level (RL) was reaching a plateau
We cut the data into blocks of equal length and the block length is set to 365, which means that every block consists of data from one year
The consequence of plotted points falls onto an straight line
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. It is well known that the Sun is a dynamic and complex body, releasing energy on all wavelength intervals of the electromagnetic spectrum [1]. Solar activity has an important impact on space climate, space navigation, and high-frequency radio communications [2]
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