Problem
I use ERA Interim Monthly Means of Daily Means data for:
- 10 metre U wind component (short name '10u', ID 165)
- 10 metre V wind component (short name '10v', ID 166)
- 10 metre wind speed (short name 10si, ID 207)
I then calculate sqrt(u10*u10+v10*v10), ie, approximate the wind speed from U and V components.
However, I the result is different form the 10 metre wind speed (10si). Why is this?
Answer
The mean wind speed (10si) is not equal to the speed of the mean wind components.
The mean wind speed for the month is produced by calculating the wind speed at each individual time within the month and then averaging over the month.
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