Sky type classification in Central England during winter

This study shows that the most frequent winter sky types in Central England are: (i) I.2 (overcast, with steep gradation and slight brightening towards the sun), with a frequency of occurrence of 19.5%, (ii) I.1 (overcast, with steep gradation and with azimuthal uniformity) (10.5%) and (iii) II.1 (overcast, moderately graded, with azimuthal uniformity) (9.7%). The most predominant cloudless sky is V.5 (cloudless, polluted, with a broad solar corona), with a frequency of occurrence of 7.6%.