Question

Which one of the following defines Aridity Index $\left(AI\right)$?

(where AET = Actual Evapotranspiration and PET = Potential Evapotranspiration)

• A. $AI=\frac{\text{PET - AET}}{\text{PET}}\times 100$
• B. $AI=\frac{\text{PET}}{\text{AET}}\times 100$
• C. $AI=\frac{\text{AET}}{\text{PET}}\times 100$
• D. $AI=\frac{\text{AET - PET}}{\text{AET}}\times 100$

Answer 1

The correct option is A $AI=\frac{\text{PET - AET}}{\text{PET}}\times 100$

The departure of AI from its corresponding normal value is known as AI anomaly, represents moisture shortage. Based on AI anomaly, the intensity of agricultural drought is classified as follows:

$\begin{array}{cc}\text{AI anomaly}& \text{Severity class}\\ 1-25& \text{mild arid}\\ 26-50& \text{moderate arid}\\ >75& \text{severe arid}\end{array}$