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The centimetric index is the measured radio flux of the whole sun at 10.7 cm wavelength. It is available since 1947. Its unit is in 10-22W/m2/Hz. It is presently measured by Penticton observatory (Canada). The centimeter flux is a proxy of the UV solar flux which modulates the Earth atmosphere ionisation and warming. It is used to forecast, amongst other thing, radiopropagation and atmospheric drag on satellites.The centimeter flux can be deduced from RI12 using the following approximation (the correlation coefficient is 0.9962):
F10.7 = 57.06 + 0.968223 x RI12 (+ Δobs)*

The blue bars are calculated monthly mean values and the orange dash line is the running average over 12 months. Red and orange bars are predicted values. Orange ones are anterior to the date when the prediction was computed (delay of 6 months because of the running average calculation).
* Δobs corresponds to a fitting with recent flux measurements.