A similar-cycle method is applied in predicting the shape of Solar Cycle 25, through a more scientific definition to select similar cycles. Using the current solar minimum $R_{\mathrm{min}}(25)$ as a reference, the six most similar cycles to Solar Cycle 25 are found to be Cycles 24, 15, 12, 14, 17, and 10 (in that order). The monthly values of sunspot-number series for the whole of Cycle 25 are predicted by weighted averaging the corresponding ones in the six similar cycles. As a result, Solar Cycle 25 is predicted to peak around October 2024 with an amplitude of about $R_{\mathrm{m}}=137.8\pm 31.3$ and to end around September 2030. As a by-product, there might be a secondary peak eight months earlier. The similar-cycle method considers only the solar cycles with similar parameters rather than all ones as for regression methods. It has an advantage that it does not depend so much on the accuracy of the observation.

中文翻译：

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使用类似周期方法预测太阳周期的形状 25

应用相似周期法预测太阳周期25的形状，通过更科学的定义来选择相似周期。使用当前的太阳活动极小值 $R_{\mathrm{min}}(25)$ 作为参考，发现与太阳活动周期 25 最相似的六个周期是周期 24、15、12、14、17 和 10（在那个顺序）。整个第 25 周期的太阳黑子数序列的月值是通过对六个相似周期中相应的加权平均来预测的。因此，预计太阳活动周期 25 将在 2024 年 10 月左右达到峰值，振幅约为 $R_{\mathrm{m}}=137.8\pm 31.3$，并在 2030 年 9 月左右结束。作为副产品，可能会有八个月前的第二个高峰。相似周期法只考虑参数相似的太阳周期，而不像回归方法一样考虑所有的太阳周期。