Validation of Significant Wave Height from Satellite Altimeter in the Seas around Korea and Error Characteristics

Abstract

Oceanic surface waves are generated by winds blowing over the oceanic surface of which the strength depends on how strong, how long, and how far the winds blow (Kinsman, 1965;Knauss, 1996). Since the waves can travel far from their origin of propagation to over thousands of kilometers as swell, they can have remarkable influences on non-local remote coastal regions. Therefore, the waves at local coastal stations Abstract : Significant Wave Height (SWH) data measured by satellite altimeters (Topex/Poseidon, Jason-1, Envisat, and Jason-2) were validated in the seas around Korea by comparison with wave height measurements from marine meteorological buoy stations of Korea Meteorological Administration (KMA). A total of 1,070 collocation matchups between Ku-band satellite altimeter data and buoy data were obtained for the periods of the four satellites from 1992 to the present. In the case of C-band and S-band observations, 1,086 matchups were obtained and used to assess the accuracy of satellite SWH. Root-Mean-Square (RMS) errors of satellite SWH measured with Ku-band were evaluated to roughly 0.2 _ 2.1 m. Comparisons of the RMS errors and bias errors between different frequency bands revealed that SWH observed with Ku-band was much more accurate than other frequencies, such as C-band or S-band. The differences between satellite SWH and buoy wave height, satellite minus buoy, revealed some dependence on the magnitude of the wave height. Satellite SWH tended to be overestimated at a range of low wave height of less than 1 m, and underestimated for high wave height of greater than 2 m. Such regional characteristics imply that satellite SWH should be carefully used when employed for diverse purposes such as validating wave model results or data assimilation procedures. Thus, this study confirmed that satellite SWH products should be continuously validated for regional applications.Key Words : significant wave height, satellite altimeter, Ku-band, validation Korean Journal of Remote Sensing, Vol.29, No.6, 2013, pp.631~644 http://dx.doi.org/10.7780/kjrs.2013 -6 31 -

Toward a High-Resolution Wave Forecasting System for the Changjiang River Estuary

“…The diversion between different altimeter observations further suggests that the Sentinel-3A/3B may overestimate the H s during fair weather conditions in the ECS. Indeed, the H s overestimation of altimeter during low wave conditions has been frequently reported [48,54,55]. Given the possible errors in the altimeter observations, the skill statistics between the simulated waves and the observations represent mainly the differences rather than the errors, and they are referred to as representation errors, which are distinct from the model errors and the measurement errors [56].…”

“…Most of the comparisons, how ever, are over the open ocean or around the American continent since the matchup is rel atively sparse in the regional applications. Based on four nearshore sites around the Korea Peninsula, Park et al [54] suggested that Hs measured by Topex/Poseidon, Envisat, and The overestimation of H s in the summer is partly due to the errors in the GFS winds. Jiang et al [24] assessed the performance of five different winds, including ERA5, CFSv2, GFS, CCMP, and the APRCP, and found that the mean GFS wind in the summer was approximately 0.5 m/s higher than ERA5 and outweighed the ERA5 in both fair weather and extreme weather conditions, particularly in extreme weather events.…”

“…Most of the comparisons, however, are over the open ocean or around the American continent since the matchup is relatively sparse in the regional applications. Based on four nearshore sites around the Korea Peninsula, Park et al [54] suggested that H s measured by Topex/Poseidon, Envisat, and Jason-1/2 tended to be overestimated at low wave heights (<1 m) and underestimated at high wave heights (>2 m). Our results also show that all three altimeter observations overestimate the H s during low wave conditions in the ECS, especially for Sentinel-3A/3B.…”