is this what you need? Is the annual mean calculated as the average of the monthly means? if yes, the annual mean and the SI is automatically calculated by the template... the year numbers can of course be changed.
best, martin
Will I have to divide the SI value by 12 or use the raw result? The SI value normally ranges between 0 to 1.83.
Hello Suman, I made a mistake in my thinking... my bad! However your suggestion was not the right one. I replaced the corrected Excel file.
Just in case you want to know what I did in the template...
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Understanding the variables
- i is a variable that stands for a month in the given year, it therefore can be a whole number between 1 and 12
- xi is the average rainfall in the i-th month
- R is the total (mean) rainfall in that year if the value is negative, make it simply positive
Step 4: Sum up all twelve values obtained in Step 3
Step 5: Divide the sum from Step 4 by the calculated R from step 1
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In Excel
Cells B3 to B14 are the mean monthly rainfalls. In B15 I calculate R which can be achieved by the following formula:
=SUM(B3:B14)
I added a condition in which the value is only displayed if all values for xi are added
=IF(COUNT(B3:B14)
As I understand Walsh & Lawler's (1981) Seasonality Index (SI), R should be mean annual rainfall and not total rainfall in a year. They were explicit about this. Try looking up their paper. I think the preceding is flawed in its interpretation of R from the formula.
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