Model of the monthly temporal averaging of daily data built from two components: linear component and constant lower background at 70.5 sfu. The pink crosses are the synthesized daily values. The green dots are the corresponding monthly mean values, and the blue line is the non-parametric local mean of those values. As a comparison, the black line is the 4th-order polynomial fitted to the real monthly mean data (Table 3), with uncertainties (black dashes lines).