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Temperature and salinity distribution characteristics in seas around Japan, and statistical parameters used in a visual quality-control software

 

Yutaka Nagata1, Toru Suzuki1, Sachiko Oguma1, Shizuo Iwata1, Hidetoshi Watanabe2 and Tomoichi Yoshimura3

1 Marine Information Research Center, Japan Hydrographic Association

2 Sanyo Techno Marine, Inc.

3 PASCO Environmental Science Institute

 

1. Introduction

 

Range checks on temperature, salinity and their vertical gradients, and density inversion check are very effective in quality-control procedure of oceanic data, and are used by almost all data management organization in the world. For example, (US) NODC made a quality-control on their database by used this technique prior to compile World Ocean Dataset 1998 (WOD98). However, the reasonable or permissive ranges of values are usually by NODC are very wide, and its purpose appears to detect errors caused by clear mistypes. NODC set the ranges for 9 sub-domains of the worldwide ocean (Fig. 1), and whole North Pacific Ocean except its equatorial region is considered one sub-domain. If we confine our attention to the limited area, we would be able to set more precise ranges for higher level quality-control software. We selected two unique areas in vicinity of Japan as test areas: the Mixed Water Region to the east of Honshu and the Kuroshio Region to the south of Honshu. The Mixed Water Region between Oyashio and Kuroshio Fronts are very complicated, and the distribution patterns of temperature and salinity would be very skewed because three kinds water masses, Oyashio Water, Tsugaru Current Water and Kuroshio Water, intrude into this region. On the other hand, the Kuroshio has two stable flow patterns, Straight Path and Meandering Path, to the south of Honshu. The bi-modal structure of the Kuroshio would influence the distribution patterns inevitably. In this paper we introduce our results of analysis mainly for these regions, and propose the range parameters to be used in a quality-control software of higher level.

 

2. The Mixed Water Region to the east of Honshu

 

The Iwate Fisheries Technology Center has conducted oceanic observation along the 4 observation lines shown in Fig.2, on monthly base from 1963. All observed values of temperature (left) and of salinity (right) observed in the period from 1971 to 1995 are plotted against depth in Fig. 3. The curves consist of vertical and horizontal lines indicate the permissible ranges adopted by NODC. Though the distribution ranges in the region under consideration are considerably wide in this region, the ranges used by NODC is clearly too wide to make a high quality-control. We calculated the means (m) and the standard deviations (σ) for each standard depth, and m and m±3σ are plotted with white triangles and white circles in Fig. 3. If the distribution is Gaussian, 99.7% of the data would lie in the range of m±3σ.

 

 

 

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