Climate and Wine Quality: Relative humidity and evaporation

Appears in

Oxford Companion to Wine

Oxford Companion to Wine

By Jancis Robinson

Published 2006

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Strong evaporative demands place the vines under water stress, which, in extreme cases, can cause leaf loss and substantial collapse of vine metabolism. Obvious fruit damage often follows through excessive exposure to the overhead sun. Milder water stress can still reduce photosynthesis and sugar production in the leaves, and hence reduce both quantity and fruit quality. Mechanisms are discussed more fully under evaporation and humidity.

Virtually all of the world’s acknowledged great table wines have so far come from regions with moderately high relative humidities and low evaporation. This is partly because of their lack of stress (see above) and perhaps through their usually restricted temperature variability.