Monthly smooth hemispheric sunspot numbers

Time range: 1/1992 - last elapsed month (provisional values)

Data description:
Monthly smoothed mean total and North/South sunspot numbers. The 13-month smoothed monthly sunspot numbers are derived by a "tapered-boxcar" running mean of monthly hemispheric sunspot numbers over 13 months centered on the corresponding month (Smoothing function: equal weights = 1, except for first and last elements (-6 and +6 months) = 0.5, Normalization by 1/12 factor). This is the same smoothing as the standard smoothing applied to the total monthly sunspot numbers. There are no smoothed values for the first 6 months and last 6 months of the file: columns 4, 5 and 6 are set to -1 (no data).

Choice of smoothing:
This 13-month smoothed series is provided only for backward compatibility with a large number of past publications and methods resting on this smoothed series. It has thus become a base standard (e.g. for the conventional definition of the times of minima and maxima of solar cycles).

However, a wide range of other smoothing functions can be used, often with better low-pass filtering and anti-aliasing properties. As the optimal filter choice depends on the application, we thus invite users to start from the monthly mean Sunspot Numbers and apply the smoothing function that is most appropriate for their analyses. The classical smoothed series included here should only be used when direct comparisons with past published analyses must be made.

Error values:
For total Sunspot Numbers, the standard deviations in this files are obtained from the weighted mean of the variances of the 13 months in the running mean value:
sigma(ms)=sqrt(SUM(weigth(M)*sigma(M)^2)/SUM(weight(M))
where sigma(M) is the standard deviation for a single month, weight(M) is 1 or 0.5 and M is over 13 months in this case.

The standard deviations for the hemispheric values are estimated by the weighted mean (squared) of the error on the monthly mean total sunspot number.

As successive monthly means are highly correlated, the standard error on the smoothed values can be estimated by the same formula as for a single month: sigma/sqrt(N) where sigma is the listed standard deviation and N the total number of observations in the month.
The number of observations given in column 6 is the number of observations of the corresponding (middle) month: same value SUM N(d) as in the monthly mean file.
This thus gives a smoothed mean of monthly standard deviations, i.e. with the samme low-pass filtering as the data value itself. Further autocorrelation analyses will be needed to derive a conversion of this standard deviation to a standard error of the 13-month smoothed number.

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TXT
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Filename: SN_ms_hem_V2.0.txt
Format: plain ASCII text

Contents:
Column 1-2: Gregorian calendar date
- Year
- Month
Column 3: Date in fraction of year for the middle of the corresponding month
Column 4: Monthly smoothed total sunspot number.
Column 5: Monthly smoothed North sunspot number.
Column 6: Monthly smoothed South sunspot number.
Column 7: Monthly mean standard deviation of the raw total sunspot number data.
Column 8: Monthly mean standard deviation of the raw North sunspot number data.
Column 9: Monthly mean standard deviation of the raw South sunspot number data.
Column 10: Number of observations used to compute the corresponding monthly mean total sunspot number.
Column 11: Number of observations for the monthly mean north sunspot number (not used yet)
Column 12: Number of observations for the monthly mean south sunspot number (not used yet)
Column 13: Definitive/provisional marker. A blank indicates that the monthly mean values are definitive. A '*' symbol indicates that the monthly values are still provisional and are subject to a possible revision (Usually the last 3 to 6 months)

Line format [character position]:
- [1-4] Year
- [6-7] Month
- [9-16] Decimal date
- [19-23] Monthly smoothed total sunspot number
- [25-29] Monthly smoothed North sunspot number
- [31-35] Monthly smoothed South sunspot number
- [38-42] Standard deviation (Total)
- [44-48] Standard deviation (North)
- [50-54] Standard deviation (South)
- [57-60] Number of observations (Total)
- [62-65] Number of observations (North)
- [67-70] Number of observations (South)
- [72] Definitive/provisional indicator

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CSV
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Filename: SN_ms_hem_V2.0.csv
Format: Comma Separated values (adapted for import in spreadsheets)
The separator is the semicolon ';'.

Contents:
Column 1-2: Gregorian calendar date
- Year
- Month
Column 3: Date in fraction of year for the middle of the corresponding month (~ day 15)
Column 4: Monthly smoothed total sunspot number.
Column 5: Monthly smoothed North sunspot number.
Column 6: Monthly smoothed South sunspot number.
Column 7: Monthly mean standard deviation of total sunspot number data
Column 8: Monthly mean standard deviation of North sunspot number data
Column 9: Monthly mean standard deviation of South sunspot number data
Column 10: Number of observations for the monthly mean total sunspot number.
Column 11: Number of observations for the monthly mean north sunspot number (not used yet)
Column 12: Number of observations for the monthly mean south sunspot number (not used yet)
Column 13: Definitive/provisional marker. '1' indicates that the value is definitive. '0' indicates that the value is still provisional.