Sunday, October 13, 2013

A More Precise Time Scale Has Little Effect On Anomaly Fits

  I tried a more precise time scale using the day of the year for the center of the months divided by the number of days in the year for the position of a month in fractions of a year instead of just dividing the number of the month by twelve and got a barely noticeable change in the coefficients of the terms for the global land anomaly fit. One reason was that the difference in years from the center of the range of the 20-year average for the anomaly data was used in the formula to be fitted so a 15 day shift in time wouldn't have much of an effect. This justifies the use of the simpler approximation.

The day-of-year function above for the Gregorian Calendar was a variation of the one used in an earlier post and uses the year, month and day as variables and first decides if the year was a leap year before using the older doy function. One line of NOAA's anomaly data gave the year, the month and the mean anomaly for the month.

Supplemental (Oct 13): For the middle of the month one should use the average of the first and last days of the months which requires the day before the second doy and so one has to subtract one from the numerator in the second line above. (Sorry, it was a typo made in the wee hours of the night.)

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