(a) Daily values of a weighted-average and the 81-day filtered “new” composite (red) and for comparison the 81-day filtered PMOD composite (blue). (b) Number of records used for each daily value and (c) the rms deviation of the weighted average and the difference between the two composites. Note the jump during 1978, which is due to an incorrect extension of the PMOD composite with the results of a proxy model.