Study of density range with seasonal variation in the water-mass structure

Taiyo Kobayashi1, Yasuko Ichikawa1, Yasushi Takatsuki2, Toshio Suga1, Keisuke Mizuno2, Naoto Iwasaka1, Nobuyuki Shikama1, and Kensuke Takeuchi1

Abstract

Considering the seasonal variability in the sea surface layer, we can check the Argo data with much higher quality. By using statistic methods, we examined the density ranges with seasonal variation in the water-mass structure. Against our expectations, many regions have seasonal variations even in the deep layers. It is probably caused by the characters of the oceanographic data as the following:

  1. Comparing the accuracy of the statistic tests, most salinity data has lower resolution.
  2. Oceanographic data is apt to be biased for the limited surveyors, periods, and regions in the observations, especially in the case of small observations.
Key words: Argo project, Quality Control, Seasonal variability

1: Frontier Observational Research System for Global Change, Climate Variations Observational Research Program
2: Japan Marine Science and Technology Center, Ocean Research Development


1. Introduction


Fig. 1: Distribution of the climatological data in the western North Pacific.

2. Statistic Test

3. Results

3.1 Areas fir statistic test


Fig. 2: Distribution of the seasonal data in the studied subtropical region. The light-blue, red, blue, and yellow circles represent the data observed in winter, spring, summer, and autumn, respectively. The stars and circles at the lower left corners show the region where the seasonal variations exist in deep layers or not, respectively.


Fig. 3: Same as Fig. 2 but for the Mixed Water Region.

3.2 Subtropic regions


Fig. 4: Results of the statistic test for 1214_8h region. See text for the details.


Fig. 5: Horizontal distribution of the potential density at 25 m depth in winter.


Fig. 6: Same as Fig. 4 but for 1213_6h.

3.3 Mixed water region


Fig. 7: Same as Fig. 4 but for 1314_Eh.


Fig. 8: Same as Fig. 4 but for 1314_Bh.

4. Discussions

4.1 Criterious of statistic test

4.2 Details of the check in each region

4.2.1 Area of 1213_6h


Fig. 9: Horizontal distribution and T-S diagram of the seasonal data in 1213_6h area. @ The light-blue, red, blue, and yellow circles represent the data observed in winter, spring, summer, and autumn, respectively.


Fig. 10: Horizontal distribution and T-S diagram of the autumn@data in 1213_6h area. The red and orange represent the data observed by R/V Priboy (USSR) in Oct. 1980. The light-blue represents the other autumn data.


Fig. 11: Horizontal distribution and T-S diagram of the winter/summer data in 1213_6h area. Blue and light-blue represent the winter data, and red and orange represent the summer data. The blue and red is the observation by R/V Ryofu (JMA).

4.2.2 Area of 1314_Bh

B


Fig. 12: Same as Fig. 9 but for 1314_Bh area.


Fig. 13: Time-series of the number of salinity data in 1314 area. The red, green, and blue represent the data whose resolution are 0.1, 0.01, and 0.001 psu, respectively.