I am conducting experiments to collect wind speed data from wind anemometers placed on a moving platform. Closely, there is a fixed wind mast holding a wind vane. Prior to analysing the wind data from the moving platform, I binned the data with 1-minute average wind direction. Each bin contains a number of continuous data sets (Set 1, Set 2, Set 3 etc.) which may not necessarily have the same number of data points. For example, Set 1 has 20,000 data points, Set 2 has 6,000 data points, etc.
I am performing an FFT on each of the sets to detect any periodicities in the signal. I am plotting the real amplitude of the sinusoids present in the signal on the y-axis vs. the frequency of the sinusoid. The FFT of each data set is yielding different amplitude results, on the y-axis and I'm not sure whether this is a result of the different length of the arrays. I am interested in an average value of the y-axis of the spectrum. However, I don't think that it is suitable to just calculate the average due to the different array size. Can someone please suggest a method? I am not used to analysis of signals in this way so I'm a bit confused. Thanks a lot.