Integral activity of the declining phase of sunspot cycles as precursor of the next cycle

In this paper, we address the prediction of the amplitude of the 11-year solar cycle as described by the 13-month averaged sunspot number time-series. We introduce a new characteristic, namely the “integral activity”, that is considered as precursor of the next cycle. We demonstrate a clear relationship between the maximum amplitude of the sunspot cycle and features of this integral activity. Two relevant indicators are constructed from these features. The first determines if the amplitude of the next cycle will be larger or smaller compared with the current one and is validated by a perfect agreement for all cycles from 1 to 23. The second is used to obtain quantitative reconstructions of the next cycle's maximum sunspot number during the modern era (cycles 10–23). The linear regression created on the basis of this indicator gives estimates of the next maximum of the smoothed sunspot number with a standard error of 11.2. The correlation coefficient is 0.95.