Probability distribution of wind speed and wave height in Nowshahr Port using the data acquired from wave scan buoy

Abstract

The present study aimed to determine probability density function (Pdf) of wind speed and wave height in Nowshahr Port using the data obtained from wave scan buoy. Three Pdfs, i.e. Weibull, Rayleigh and Lognormal, were adopted for estimation of data frequency. The shape (k) and scale (c) parameters of the Weibull function were calculated by four methods, i.e. Graphical method (Gm), Moment method (Mm), Maximum likelihood method (Mlm) and Empirical method (Em) whereas the parameters of the other two functions were estimated only through Mlm. In order to analyze the efficiency of pdfs root mean square error (Rmse), determination coefficient (R2) and chi-square test (χ2) were considered. The results revealed that Mm, Em and Mlm presented almost similar ‘k’ and ‘c’ values. However, Gm yielded smaller values. Accuracy of Weibull Pdf was generally higher than those in Rayleigh one. However, it was seen in the present study that Rayleigh Pdf is better only when Weibull parameters in wind data were measured via Gm. Lognormal Pdf was the most efficient in both wind and wave data. Finally, cumulative distribution function was estimated based upon Weibull and Lognormal probability models and the former was again found to be stronger and more accurate.