Revised dates for sunspot cycle peaks

Revised sunspot cycle peak dates

Introduction

Using the LOESS data to plot sunspot cycle data is the topic discussed in my previous blogs. I show that the current practice of using a moving average on sunspot data is probably not ideal and that using the LOESS procedure yields better results. 

A spin-off from using the LOESS procedure to calculate the shape of a sunspot cycle is that the peak of the sunspot cycle is calculated to be earlier than that reported using the moving average approach. I will list the revised sunspot cycle peaks that I obtained using the LOESS procedure.

Revised Sunspot Cycle Peak dates using the LOESS procedure

I did all the calculation in Excel and used the inbuilt maximum function to locate the peak of the sunspot cycles that I had data for. The results were summarized and are shown in the following tabulation:-

Table 1 - Sunspot Cycle Peak Dates

In Table 1 the revised sunspot cycle peak dates using the actual raw sunspot data (Sun Spot Count), the revised method of calculating the sunspot cycle shape (LOESS 1000) and moving average method (Ma 390) are shown. The results is a lot of dates that need to be carefully inspected to make any sense. To make this information easier to understand I created the following tabulation.

Table 2 - Deltas in Days

Note the average is calculated using the full sunspot cycles 7 to 23

In Table 2 I show the differences (deltas) in days between the various ways I used to calculate the peak date for the sunspot cycle. I used the LOESS 1000 sunspot peak date as the reference. A negative number is the number of days the other way to calculate the sunspot cycle is later than the date of the LOESS 1000 date, and using the same logic, a positive  number is the number of days the other method gives an earlier date.

Discussion

On average the moving average method of establishing the sunspot cycle peak calls the peak 184 days later than that of the LOESS method. This is approximately a  six months difference.

On average the moving average method calls the peak of the sunspot cycle 6 months too late.

How will this impact on studies that rely on sunspot data to make projections? I am not sure but will start looking whether I can find any recent papers and see what is the influence.

Lastly, sunspot cycle 24 is still ongoing and incomplete and ignored in the average calculation, as is Sunspot cycle 6.