Înţeleg că termenul descrie gradul de acoperire cu nori şi tipurile de nori observate.

v.
Data from 15 stations were used; four Australian, four European, three Canadian, and four American. In most cases three years of data were used for each station.
Cloudiness regimes from relatively cloud free (Australia and Albuquerque) to relatively cloudy (European stations) were represented.
http://www.physics.arizona.edu/~cronin/Solar/References/Irra...
http://pubs.giss.nasa.gov/abs/wi05100g.html

Regimul nefic

Norii sunt stratiformi si au o frecventa maxima in orele diminetii.
Numarul anual al zilelor innourate este de 120 - 130 si a celor senine de 110 - 120 restul zilelor fiind partial acoperite.
http://www.ppbc.ro/geografie.php?nL=luizi_calugara