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  • Author or Editor: Jae-Hun Park x
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Yongsheng Xu
,
D. Randolph Watts
, and
Jae-Hun Park

Abstract

In the Japan/East Sea, energetic high-frequency large-scale barotropic motions are shown to lead to large aliasing errors in satellite altimetry observations. The combined aliasing from several neighboring and crossing tracks produces artificial mesoscale signals in altimeter-mapped products, significantly changing the map interpretation. The alias can be well suppressed by subtracting the large-scale barotropic motions observed by bottom pressure sensors. By using coastal tide gauge data in the Japan/East Sea, about 78% of the alias source variance can be removed, which offers an alternative way to suppress the alias for other time intervals without bottom pressure measurements.

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Jae-Hun Park
,
D. Randolph Watts
,
Karen L. Tracey
, and
Douglas A. Mitchell

Abstract

This paper demonstrates a new gravest empirical mode (GEM) technique that constructs multi-index lookup tables of temperature (T) and specific volume anomalies (δ) using historical hydrocasts as a function of three indices: round-trip travel time (τ) from sea floor to the surface, sea surface temperature, and pressure. Moreover, the historical hydrocasts are separated into non-mixed-layer (NML) and mixed-layer (ML) groups, and a single GEM field is constructed for each group. This is called the MI-GEM technique. The appropriate dates for MI-GEM fields are determined by the monthly distribution of the number of NML and ML profiles in the historical hydrocasts, which are also well correlated with the strength of the winds during the 2 yr of observations. The T and δ profiles that are determined by this MI-GEM technique capture 92% and 88% of the T and δ variances in the depth range of 0–200 db. These values reduce by about one-third of the unexplained error variance of the residual GEM, which was recently developed and applied to the optimal interpolated τ data in the southwestern Japan/East Sea (JES) by Mitchell et al. Comparisons with the in situ CTD casts demonstrate that the MI-GEM technique almost always produces improved full water column profiles of T and δ. Whereas the residual GEM estimates had exhibited qualitatively erroneous features like T inversions in the near–surface layer and too thin or thick intermediate water layers in some regions, the MI-GEM estimates avoid those problems, which were inherent to the residual GEM technique in the southwestern JES.

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