National Data Buoy Center. Station FWYF1 -

Fowey Rocks, Fl


Operation Period
Latitude
Longitude
06/91 - present
25.59 N
80.10 W


Is 2003 mean wind during the summer bigger than averaged?

Is 2003 wind more persistent in time than previous years?

Is 2003 wind more persistent in direction than previous years?



The mean and standard deviation for the available wind observations for 2003 is evaluated:

2003_wind


2003 monthly wind (m/s) FWYF1 Cman
Along-shelf mean Along-shelf std Across-shelf mean Across-shelf std
Jan -2 4.38 2.06 3.96
Feb 1.55 4.1 0.498 4.3
Mar 1.47 3.95 -1.81 3.78
Apr 1.75 4.72 0.739 4.18
May 2.82 3.34 -1.24 3.37
Jun 2.96 3.38 -0.785 2.84
Jul 4.14 2.37 0.683 2.01
Aug 3.72 2.79 0.748 3.08
Sep 1.76 3.15 0.822 3.56
Oct 1.29 3.67 2.75 3.91
Nov 3.05 4.28 4.48 4.08
Dec 0.969 5.91 2.88 4.13

When we compare these values with the whole set of observations for the summer we can observe that the summer of 2003 has stronger upwelling favorable winds but the difference with previous years might not be significant.


year_comparison



T-TEST: Comparison of means

To determine if the mean winds for 2003 are significantly bigger than the ones for previous years we use Matlab TTEST2 Hypothesis test.

TTEST2 Hypothesis test: Compares the averages of two samples.
    [H,P,CI,STATS] = TTEST2(X,Y,ALPHA,TAIL) performs a t-test to
    determine whether two samples from a normal distribution (with
    unknown but equal variances) could have the same mean.
    The null hypothesis is: "means are equal".
    For TAIL =  0  the alternative hypothesis is: "means are not equal."
    For TAIL =  1, alternative: "mean of X is greater than mean of Y."
    For TAIL = -1, alternative: "mean of X is less than mean of Y."
    TAIL = 0 by default.
    H=0 => "Do not reject null hypothesis at significance level of alpha."
    H=1 => "Reject null hypothesis at significance level of alpha."


Along-shelf Mean Wind comparison (ttest) FWYF1 Cman
2003 Along-shelf mean All years Along-shelf mean means are not equal mean of 2003 is greater than mean of rest mean of 2003 is less than mean of rest
Jan -2 1.04 1 0 1
Feb 1.55 1.51 0 0 0
Mar 1.47 1.77 0 0 0
Apr 1.75 2.64 1 0 1
May 2.82 2.75 0 0 0
Jun 2.96 2.76 0 1 0
Jul 4.14 2.84 1 1 0
Aug 3.72 2.66 1 1 0
Sep 1.76 2.77 1 0 1
Oct 1.29 2.45 1 0 1
Nov 3.05 1.8 1 1 0
Dec 0.969 1.24 0 0 0


Across-shelf Mean Wind comparison (ttest) FWYF1 Cman
2003 Across-shelf mean All years Across-shelf mean means are not equal mean of 2003 is greater than mean of rest mean of 2003 is less than mean of rest
Jan 2.06 1.07 1 1 0
Feb 0.498 0.615 0 0 0
Mar -1.81 0.36 1 0 1
Apr 0.739 1 0 0 1
May -1.24 0.673 1 0 1
Jun -0.785 -0.32 1 0 1
Jul 0.683 -0.256 1 1 0
Aug 0.748 0.261 1 1 0
Sep 0.822 0.477 1 1 0
Oct 2.75 2.67 0 0 0
Nov 4.48 3.36 1 1 0
Dec 2.88 1.8 1 1 0


As can be seen from the along-shelf wind table, the mean wind for the months of June, July, and August of 2003 is significantly bigger than the mean wind for the previous years. 




Autocorrelations


To see if the wind during the summer of 2003 was more persistent than during previous years, we look at the autocorrelation of the wind data. If the wind was more persistent the correlations for every lag hour are going to be bigger than usual.


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Wind Direction Histograms


To see if the wind during the summer of 2003 was more persistent in direction than during previous years, we look at histograms of wind direction. If the wind was more persistent the histogram during the summer is going to be narrower than for the rest of the years. The blue line represents the upwelling favorable wind direction. We can see that for the summer months of 2003 the wind direction corresponds approximately with the upwelling favorable direction. The percentage of upwelling favorable wind in 2003 is higher than in previous years for June, July and August.


histogram histogram histogram
histogram histogram histogram
histogram histogram histogram
histogram histogram histogram