How to Calculate the Fournier Index
- 1). Obtain the figure for precipitation in the wettest month for the locale in question. For example, assume November is the wettest month and its mean rainfall is 5 inches.
- 2). Square the number in the previous step. In the example, 5 squared is 25.
- 3). Divide the number in the previous step by the total mean annual precipitation in the locale in question. For the example, assume annual precipitation is 35 inches. The Fournier Index is 25 divided by 35, or 0.71.
