Monthly mean total sunspot number and 13-month smoothed numbers Time range: 1/1749 - 05/2015 Data description: Monthly mean total sunspot number obtained by taking a simple arithmetic mean of the daily total sunspot number over all days of each calendar month. Monthly means are available only since 1749 because the original observations compiled by Rudolph Wolf were too sparse before that year. (Only yearly means are available back to 1700) The 13-month smoothed monthly sunspot number is derived by a "tapered-boxcar" running mean of monthly 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). There are no smoothed values for the first 6 months and last 6 months of the data series. NB: Although many other smoothing functions can be used, this method introduced by the Zurich observatory in the early 20th century still serves as a base standard (e.g. for the conventional definition of the times of minima and maxima of solar cycles). ------------------------------------------------------------------------------- TXT ------------------------------------------------------------------------------- Filename: monthssn.dat Format: plain ASCII text Contents: Column 1: Gregorian calendar date Column 2: Date in fraction of year for the middle of the corresponding month (~ day 15) Column 3: Monthly mean total sunspot number. Column 4: Definitive/provisional marker. A blank indicates that the value is definitive. A '*' symbol indicates that the monthly value is still provisional and is subject to a possible revision (Usually the last 3 to 6 months) Column 5: 13-month smoothed monthly total sunspot number. Column 6: Definitive/provisional marker as in column 4 but for the smoothed monthly values. NB: On months when the running mean cannot be calculated, columns 5 and 6 are left blank. Line format [character position]: - [1-4] Year - [5-6] Month - [9-16] Decimal date - [20-24] Monthly total sunspot number - [26] Definitive/provisional indicator for monthly numbers - [28-32] 13-month smoothed monthly total sunspot number. - [34] Definitive/provisional indicator for smoothed monthly numbers ------------------------------------------------------------------------------- CSV ------------------------------------------------------------------------------- Filename: ISSN_M_tot.csv Format: Comma Separated values (adapted for import e.g. in MS Excel) 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 mean total sunspot number. Column 5: Definitive/provisional marker. '1' indicates that the value is definitive. '0' indicates that the monthly value is still provisional and is subject to a possible revision (Usually the last 3 to 6 months) Column 6: 13-month smoothed monthly total sunspot number. Column 7: Definitive/provisional marker as in column 5 but for smoothed monthly values NB: On months when the running mean cannot be calculated, columns 6 and 7 are set to -1 (no data).