Comparison between a reanalyzed product by 3-dimensional variational assimilation technique and observations in the Ulleung Basin of the East/Japan Sea

Author Posting. © Elsevier B.V., 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Journal of Marine Systems 78 (2009): 249-264, doi:10.1016/j.jmarsys.2009.02.017.
Reanalyzed products from a MOM3-based East Sea Regional Ocean Model with a 3- dimentional variational data assimilation module (DA-ESROM), have been compared with the observed hydrographic and current datasets in the Ulleung Basin (UB) of the East/Japan Sea (EJS). Satellite-borne sea surface temperature and sea surface height data, and in-situ temperature profiles have been assimilated into the DA-ESROM. The performance of the DA-ESROM appears to be efficient enough to be used in an operational ocean forecast system. Comparing with the results from Mitchell et al. (2005a), the DA-ESROM fairly well simulates the high variability of the Ulleung Warm Eddy and Dok Cold Eddy as well as the branching of the Tsushima Warm Current in the UB. The overall root-mean-square error between 100m temperature field reproduced by the DA-ESROM and the observed 100-dbar temperature field is 2.1°C, and the spatially averaged grid-to-grid correlation between the two temperature fields is high with a mean value of 0.79 for the intercomparison period. The DA-ESROM reproduces the development of strong southward North Korean Cold Current (NKCC) in summer consistent with the observational results, which is thought to be an improvement of the previous numerical models in the EJS. The reanalyzed products show that the NKCC is about 35 km wide, and flows southward along the Korean coast from spring to summer with maximum monthly mean volume transport of about 0.8 Sv in August-September.
The major part of this works was conducted with financial support by Agency for Defense Development under the contract UD031003AD. The first and seventh authors were supported at the final stage of this work by KORDI’s research projects (PE9830Q and PG47100). The second author was supported by EAST-I Program of the Ministry of Maritime Affairs and Fisheries.