3.6 Cool Night Index
Cool Night Index (CI) is a viticultural climate index developed to estimate the nictothermal condition associated
with the grape maturation period [10]. Using minimum temperatures, the index serves as an indication of a region's
potential characteristics with respect to secondary metabolites (polyphenols, aromas, color) in grapes and wines.
This index evaluates the minimum night temperature of the month where important cultivation event occurs. In
correlation with the tea cultivation, tea plant will enter inactivity period when temperature drops below 10oC.