The periodograms for (a) blocking event occurrences, (b) precipitation, and (c) the cross-spectra of blocking and precipitation for the Moscow region covering the period 1970–2013. The abscissa is cycles per decade in (a), (b), and (c). The green (blue) line is the 90% confidence level for a red (white) noise process. The dotted line in (c) assumes only a white noise process.
