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An aridity index (AI) is a numerical indicator of the degree of dryness of the climate at a given location. The American Meteorological Society defined it in meteorology and climatology, as "the degree to which a climate lacks effective, life-promoting moisture".
In 1899, de Martonne became a professor at the University of Rennes. [4] There he founded the institute of geography on the German model. [5] In October 1905 he moved to the University of Lyon, replaced at Rennes by Antoine Vacher. [6] Four years later he moved to the Sorbonne. [4]
The northern portion of the Arid Diagonal is a result of the blocking of the trade winds by the barrier formed by the Central Andes and the South Pacific High. [5] To the south in the westerlies, the rain shadow that the Southern Andes cast over eastern Patagonia similarly blocks moisture. [1]
Higher temperatures result in higher PET. [5] Evapotranspiration (ET) is the raw sum of evaporation and plant transpiration from the Earth's land surface to atmosphere. Evapotranspiration can never be greater than PET. The ratio, Precipitation/PET, is the aridity index (AI), with an AI<0.2 indicating arid/hyperarid, and AI<0.5 indicating dry. [6]
Aridity ("drought") indexes that can be included in the article (after ): De Martonne Aridity Index; Emberger Aridity Index; UNEP Aridity Index; Thornthwaite Classification; Gaussen-Bagnouls Classification— Preceding unsigned comment added by 177.9.10.163 04:11, 2 September 2016 (UTC)
Rules are provided for combining the stress (table 3) and humidity groups (table 2) to check a box classifying the humidity and aridity for each month. For each of six possible indicators, the number of months where that indicator was checked are added up, giving a yearly total. Schematic Design Recommendations. The yearly totals in table 4 ...
Although no part of Earth is known for certain to be rainless, in the Atacama Desert of northern Chile, the average annual rainfall over 17 years was only 5 millimetres (0.20 in). Some locations in the Sahara Desert such as Kufra , Libya , record an even drier 0.86 mm (0.034 in) of rainfall annually.
The distribution of aridity at any time is largely the result of the general circulation of the atmosphere. The latter does change significantly over time through climate change . For example, temperature increase by 1.5–2.1 percent across the Nile Basin over the next 30–40 years could change the region from semi-arid to arid, significantly ...