Applicability evaluation of ERA5 wind and wave reanalysis data in the South China Sea

• Published in: Journal of oceanology and limnology 2023-03, Vol.41 (2), p.495-517
• Main Authors: Zhai, Rongwei, Huang, Caijing, Yang, Wei, Tang, Ling, Zhang, Wenjing
• Format: Article
• Language: English
• Subjects: Accuracy; Bias; Coefficients; Correlation coefficient; Correlation coefficients; Data assimilation; Design engineering; Earth and Environmental Science; Earth Sciences; Intercomparison; Limnology; Locations (working); Multi-scale marine dynamics; Natural resources; Oceanography; R&D; Research & development; sea-air interactions and forecasting technology in the South China Sea; Significant wave height; Wave data; Wave height; Wave period; Weather forecasting; Wind; Wind speed
• ISSN: 2096-5508; 2523-3521
• DOI: 10.1007/s00343-022-2047-8

Wind and wave data are essential in climatological and engineering design applications. In this study, data from 15 buoys located throughout the South China Sea (SCS) were used to evaluate the ERA5 wind and wave data. Applicability assessment are beneficial for gaining insight into the reliability of the ERA5 data in the SCS. The bias range between the ERA5 and observed wind-speed data was −0.78–0.99 m/s. The result indicates that, while the ERA5 wind-speed data underestimation was dominate, the overestimation of such data existed as well. Additionally, the ERA5 data underestimated annual maximum wind-speed by up to 38%, with a correlation coefficient >0.87. The bias between the ERA5 and observed significant wave height (SWH) data varied from −0.24 to 0.28 m. And the ERA5 data showed positive SWH bias, which implied a general underestimation at all locations, except those in the Beibu Gulf and central-western SCS, where overestimation was observed. Under extreme conditions, annual maximum SWH in the ERA5 data was underestimated by up to 30%. The correlation coefficients between the ERA5 and observed SWH data at all locations were greater than 0.92, except in the central-western SCS (0.84). The bias between the ERA5 and observed mean wave period (MWP) data varied from −0.74 to 0.57 s. The ERA5 data showed negative MWP biases implying a general overestimation at all locations, except for B1 (the Beibu Gulf) and B7 (the northeastern SCS), where underestimation was observed. The correlation coefficient between the ERA5 and observed MWP data in the Beibu Gulf was the smallest (0.56), and those of other locations fluctuated within a narrow range from 0.82 to 0.90. The intercomparison indicates that during the analyzed time-span, the ERA5 data generally underestimated wind-speed and SWH, but overestimated MWP. Under non-extreme conditions, the ERA5 wind-speed and SWH data can be used with confidence in most regions of the SCS, except in the central-western SCS.