Abstract
In view of the high cost and sparse spatial resolution of offshore meteorological observations, ocean winds retrieved from satellites are valuable in offshore wind resource assessment as a supplement to in situ measurements. This study examines satellite synthetic aperture radar (SAR) images from ENVISAT advanced SAR (ASAR) for mapping wind resources with high spatial resolution. Around 181 collected pairs of wind data from SAR wind maps and from 13 meteorological stations in Hangzhou Bay are compared. The statistical results comparing in situ wind speed and SAR-based wind speed show a standard deviation (SD) of 1.99 m/s and correlation coefficient of R = 0.67. The model wind directions, which are used as input for the SAR wind speed retrieval, show a high correlation coefficient (R = 0.89) but a large standard deviation (SD = 42.3°) compared to in situ observations. The Weibull probability density functions are compared at one meteorological station. The SAR-based results appear not to estimate the mean wind speed, Weibull scale and shape parameters and wind power density from the full in situ data set so well due to the lower number of satellite samples. Distributions calculated from the concurrent 81 SAR and in situ samples agree well.
Highlights
Wind power assessment is a fundamental work for offshore wind resources development, of which offshore wind power development presents a new growth point for renewable energy sources of the future [1], and the development of offshore wind power drives the urgent demand for offshore wind resources assessment
The overall data are included in the plot between in situ wind speed and synthetic aperture radar (SAR)-based wind speed shown in Figure 5 and winds less than 2.0 m/s in SAR-wind maps are excluded
The in situ measurements from offshore masts at Hangzhou Bay are adopted to validate the SAR wind retrievals, and the results show imperfect consistency in wind speed, comparison results in wind direction input is highly correlated with R of 0.89
Summary
Wind power assessment is a fundamental work for offshore wind resources development, of which offshore wind power development presents a new growth point for renewable energy sources of the future [1], and the development of offshore wind power drives the urgent demand for offshore wind resources assessment. The study area in this paper, Hangzhou Bay, is a typical region with abundant offshore wind resources in China. The in situ data is capable of continuously observing a local place for a long period, but has a limited spatial coverage, and high cost on human and material resources; the satellite observation is capable of obtaining the spatial distribution of the sea surface wind speed, but has a relatively low temporal resolution, with observations conducted only once or twice a day or several times every week [2]
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