Aridity indexes are quantitative indicators of the degree of water deficiency present at a given location. A variety of aridity indexes have been formulated, although the term Aridity Index specifically refers to the 1948 work of Thornthwaite. Aridity indexes have been applied at continental and subcontinental levels and are most commonly related to distributions of natural vegetation and crops. Critical values of the indexes have been derived from observed vegetation boundaries. For instance, Köppen’s 1918 classification defines the desert/steppe boundary as the 200-mm annual isohyet in regions where there is no seasonality of rainfall and the mean annual temperature is 5–10°C.
Formulation of aridity indexes is not straightforward due to the nature of aridity. First, aridity is a function of the interplay between rainfall, temperature, and evaporation. Use of mean annual rainfall as an index of aridity ignores the importance of temperature and evaporation. Aridity indexes that have...
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Cross-references
Arid Climates
Desertification
Deserts
Drought
Water Budget Analysis
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J., S. (2005). Aridity Indexes. In: Oliver, J.E. (eds) Encyclopedia of World Climatology. Encyclopedia of Earth Sciences Series. Springer, Dordrecht . https://doi.org/10.1007/1-4020-3266-8_17
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