Mean annual precipitation deficit (mm)

The monthly difference between precipitation and potential evaporation (pan, free-water surface), without accounting for soil buffering capacity on water availability (after Harmsen et al. (2009), adapted from De Pauw (2002)). Also known as water deficit or hydrological deficit. Values are negative when evaporation demand is greater than rainfall.

该指标为降水量与潜在蒸散发（蒸发器、自由水面）的月差值，未考虑土壤对水分有效性的缓冲能力，改编自De Pauw(2002)，基于Harmsen等(2009)的研究。其亦被称为水分亏缺或水文亏缺。当蒸散发需求大于降水量时，该指标取值为负值。