The Probability Distribution of Sea Surface Wind Speeds. Part II Dataset Intercomparison and Seasonal Variability

• Published in: Journal of climate Vol. 19; no. 4; pp. 521 - 534
• Main Author: Monahan, Adam Hugh
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 15.02.2006
• Subjects: Approximation; Buoys; Data analysis; Datasets; Distribution; Earth, ocean, space; Exact sciences and technology; External geophysics; General circulation models; Intercomparison; Laboratories; Marine; Mathematical moments; Mean; Mean winds; Meteorology; Northern Hemisphere; Oceanography; Oceans; Parameters; Probability; Probability distribution; Probability distributions; Probability theory; Random variables; Satellite imagery; Satellite observation; Scatterometers; Sea surface; Seas; Seasonal variability; Seasonal variation; Seasonal variations; Skewed distribution; Skewness; Special Sensor Microwave Imager; Standard deviation; Statistical analysis; Statistics; Surface wind; Time series; Velocity; Weibull distribution; Wind; Wind speed; Wind velocity; Winds; Winds and their effects; PS, Antarctic Ocean; Sea surface; world ocean; Marine atmosphere; Space remote sensing; Wind velocity; Satellite observation; Probability distribution; Scatterometer; Planetary scale; Observation data; spatial variations; statistical analysis; Weibull distribution; Microwave radiometry; seasonal variations; Surface wind
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/JCLI3641.1

The statistical structure of sea surface wind speeds is considered, both in terms of the leading-order moments (mean, standard deviation, and skewness) and in terms of the parameters of a best-fit Weibull distribution. An intercomparison is made of the statistical structure of sea surface wind speed data from four different datasets: SeaWinds scatterometer observations, a blend of Special Sensor Microwave Imager (SSM/I) satellite observations with ECMWF analyses, and two reanalysis products [NCEP–NCAR and 40-yr ECMWF Re-Analysis (ERA-40)]. It is found that while the details of the statistical structure of sea surface wind speeds differs between the datasets, the leading-order features of the distributions are consistent. In particular, it is found in all datasets that the skewness of the wind speed is a concave upward function of the ratio of the mean wind speed to its standard deviation, such that the skewness is positive where the ratio is relatively small (such as over the extratropical Northern Hemisphere), the skewness is close to zero where the ratio is intermediate (such as the Southern Ocean), and the skewness is negative where the ratio is relatively large (such as the equatorward flank of the subtropical highs). This relationship between moments is also found in buoy observations of sea surface winds. In addition, the seasonal evolution of the probability distribution of sea surface wind speeds is characterized. It is found that the statistical structure on seasonal time scales shares the relationships between moments characteristic of the year-round data. Furthermore, the seasonal data are shown to depart from Weibull behavior in the same fashion as the year-round data, indicating that non-Weibull structure in the year-round data does not arise due to seasonal nonstationarity in the parameters of a strictly Weibull time series.