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The Gaussen Index (or Bagnouls-Gaussen Index) or xerothermic index is a method of calculating and comparing aridity.
According to Henri Gaussen (French botanist and biogeographer), a given period is said to be arid, when: . [1] [2]
(P: total precipitation in millimeters over the given period, T: average temperature in °C over the given period)
The resulting index number indicates the number of biologically dry days in a year for a given location (it therefore ranges between 0 and 365). The data includes not only precipitation stricto sensu but also fog, dew and humidity of the air.
In general, it is accepted that an environment is non-arid when the index is less than 100, semi-arid between 100 and 290, arid between 290 and 350, and hyperarid between 350 and 365.
This index is very useful for the use of an ombrothermic diagram , the latter always constructed on the scale model: 1 °C = 2 mm precipitation.
Other indices such as the Louis Emberger rainfall quotient (which is not unique) have been defined. However, the Gaussen index which is simple and precise is still preferable. [3] Indeed Henri Gaussen defines precisely the 4 nuances of Mediterranean climate just against this index, [4] while Emberger defines the level of humidity in a region of Mediterranean climate but does not support precisely this Mediterranean climate. [3]
The calculation does not reflect reality because it is based on averages. For example, according to the calculation, we find a total of 0 biologically dry days in Lyon, for 60 biologically dry days in Marseille. [5]
You can help expand this article with text translated from
the corresponding article in Spanish. (September 2021) Click [show] for important translation instructions.
|
The Gaussen Index (or Bagnouls-Gaussen Index) or xerothermic index is a method of calculating and comparing aridity.
According to Henri Gaussen (French botanist and biogeographer), a given period is said to be arid, when: . [1] [2]
(P: total precipitation in millimeters over the given period, T: average temperature in °C over the given period)
The resulting index number indicates the number of biologically dry days in a year for a given location (it therefore ranges between 0 and 365). The data includes not only precipitation stricto sensu but also fog, dew and humidity of the air.
In general, it is accepted that an environment is non-arid when the index is less than 100, semi-arid between 100 and 290, arid between 290 and 350, and hyperarid between 350 and 365.
This index is very useful for the use of an ombrothermic diagram , the latter always constructed on the scale model: 1 °C = 2 mm precipitation.
Other indices such as the Louis Emberger rainfall quotient (which is not unique) have been defined. However, the Gaussen index which is simple and precise is still preferable. [3] Indeed Henri Gaussen defines precisely the 4 nuances of Mediterranean climate just against this index, [4] while Emberger defines the level of humidity in a region of Mediterranean climate but does not support precisely this Mediterranean climate. [3]
The calculation does not reflect reality because it is based on averages. For example, according to the calculation, we find a total of 0 biologically dry days in Lyon, for 60 biologically dry days in Marseille. [5]