Agricultural Drought Phenomenon in Latin America with Focus on Brazil - Monitoring and Predicting Agricultural Drought: A Global Study - page 160

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[160

Line
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-0.8
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Norm
PgEn

[160

Fig ure 12.4 Monthly variation in the difference between precipitation (P) and potential
evapotranspiration (PET) for different locations in Argentina, Brazil, Chile, and Paraguay.

and Paraguay in figure 12.4. This anomaly can be used as a drought indi-
cator. The anomaly is positive for some hot and humid regions, negative
during certain times of the year for other regions, and negative throughout
the year for semiarid and arid regions where drought is a common phe-
nomenon.

A ridity Index

The aridity index (AI) is the ratio of annual water deficiency (DEF) to PET
which is determined by the methodology proposed by Thornthwaite and
Mather (1955):

DEF
PET

100

AI = [12.1]

Based on the above index, various locations in Argentina, Brazil, Chile,
and Paraguay have been categorized into different climate types (table
12.2).