The Study of Single Station Inverting the Sea Surface Current by HF Ground Wave Radar Based on Adjoint Assimilation Technology

This paper introduces the assimilation technology in an ocean dynamics model and discusses the feasibility of inverting the sea surface current in the detection zone by assimilating the sea current radial velocity detected by single station HF ground wave radar in ocean dynamics model. Based on the adjoint assimilation and POM model, the paper successfully inverts the sea surface current through single station HF ground wave radar in the Zhoushan sea area. The single station HF radar inversion results are also compared with the bistatic HF radar composite results and the fixed point measured results by Annderaa current meter. The error analysis shows that acquisition of flow velocity and flow direction data from the single station HF radar based on adjoint assimilation and POM model is viable and the data obtained have a high correlation and consistency with the flow field observed by HF radar.

Sea surface temperature data from coastal observation stations:quality control and semidiurnal characteristics

Sea surface temperature(SST)data obtained from coastal stations in Jiangsu,China during 20102014 are quality controlled before analysis of their characteristic semidiurnal and seasonal cycles,including the correlation with the variation of the tide.Quality control of data includes the validation of extreme values and checking of hourly values based on temporally adjacent data points,with 0.15℃/h considered a suitable threshold for detecting abnormal values.The diurnal variation amplitude of the SST data is greater in spring and summer than in autumn and winter.The diurnal variation of SST has bimodal structure on most days,i.e.,SST has a significant semidiurnal cycle.Moreover,the semidiurnal cycle of SST is negatively correlated with the tidal data from March to August,but positively correlated with the tidal data from October to January.Little correlation is detected in the remaining months because of the weak coastal offshore SST gradients.The quality control and understanding of coastal SST data are particularly relevant with regard to the validation of indirect measurements such as satellite-derived data.

Preliminary assessment of ERA5 wind data in Jiangsu sea area

ERA5 data and station observation data are both of great importance in studying the regional meteorological and environmental characteristics.The accuracy of ERA5 reanalysis wind field data was evaluated using observations at five offshore platforms in Jiangsu sea area in this study.Results revealed that ERA5 wind speed was generally in reasonable agreement with that observed at each station,and that the accuracy of ERA5 wind speed data was significant better than that of wind direction.The consistency of wind direction between ERA5 and each observation station was better in autumn and winter than that in spring and summer.With increasing wind speed,the mean absolute error and root mean squared error between the ERA5 and observed wind speed(direction)data increased(decreased)obviously.During periods of typhoon,ERA5 wind data were largely consistent with observational data in terms of increasing wind speed and changing wind direction;however,the ERA5 wind speeds were slightly low.The findings of this study could provide a basis for the application and further research of ERA5 wind data in Jiangsu offshore sea area.