Octa

It has been shown that most of the flood-rainy days are associatied with 6-8 octa ScFb, CuSc in the morning and CuSc, ScFb with or without Cb in the afternoon of the previous day.

Source: wiktionary

This method does not give any information on the distribution of clouds in the sky dome. But it presents the advantage of an objective method by eliminating the source of error due to personal appreciation of the fraction of the sky covered by clouds, as is the case in the classical climatorlogical observation of the cloudiness expressed in octa (N = 0 corresponding to cloudless sky and N = 8, to overcast sky in this scale).

Source: wiktionary

In Figure 4 we compare the photolysis frequencies of different processes in scatter plots, including all measurements from the field campaign over a variety of meteorological conditions (χ = 40-90°, 296-380 DU total ozone, 0-8 octa cloud cover, 9-35 °C ambient temperature).

Source: wiktionary