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

Wind and wave data are essential to climatological and engineering applications. In this study, measured data from 15 sets of buoys located almost all over the South China Sea (SCS) are used to evaluate the applicability of ERA5 wind speed, significant wave height (SWH) and mean wave period (MWP) reanalysis data. The applicability evaluation is beneficial to gain insight about the reliability of ERA5 data in the SCS. The range of bias between ERA5 and observational wind speed is between -0.78 and 0.99 m/s. The result indicated that there exist both overestimation and underestimation of ERA5 wind speed data, but mainly underestimation. Besides, ERA5 data underestimated annual maximum wind speed, up to 38 %. The correlation coefficients between ERA5 and observational wind speed are more than 0.87. The bias between ERA5 and observational SWH varies from -0.24 to 0.28 m. ERA5 data show positive SWH biases implying a general underestimation in all locations, except for locations in the Beibu Gulf and central-western SCS where overestimation is observed. During extreme conditions, such as cold air and typhoons, an underestimation of annual maximum SWH in ERA5 data up to 30 % is observed. The correlation coefficients between ERA5 and observational SWH in all locations are more than 0.92, except for 0.84 in the central-western SCS. The bias between ERA5 and observational MWP varies from -7.4 to 0.57 s. ERA5 data show negative MWP biases implying a general overestimation in all locations, except for B1 and B7 where underestimation is observed. The correlation coefficient between ERA5 and observational MWP in the Beibu Gulf was the smallest (0.56), those of other locations fluctuate within a narrow range from 0.82 to 0.9. The intercomparison indicates that, during the analyzed time span, ERA5 data generally underestimated wind speed and SWH, whereas have an overestimation of MWP. And under non-extreme conditions, ERA5 wind speed and SWH data can be used with confidence in the SCS except for the central-western SCS