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Oceangraphy
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Study of Oceanographic Environments of sea of Harima during Red Tides period by means of Multi Platform Remote Sensing
Data used for analysis and methods
- NOAA AVHRR data
Cloud free NOAA AVHRR data obtained during the summer of 1987 (Red tides occurred) and 1985 (not occurred) were used to compare SST distribution and a horizontal extent of mixing area in the surface layer around naruto Channel due to the ebb and flow. The data used for this study are listed on table 1. IN order to compare the difference between oceanic environments during two periods, 23 images of NOAA AVHRR data from 15 JUL to AUG 1985, and 14 from 8 JUL to 30 AUG 1987, were analyzed.
- Airborne MSS data
The mixing water body formed around the Naruto Channel due to the ebb and flow affects to SST distribution in Sea of Harima. As each SST distribution estimated from NOAA AVHRR data shows oceanic feature in different tide stage, the maximum extent of mixing area is difficult to know.
- Eather observation data
Nutrients and benthic C. antique cells are often supplied into the photic zone form the bottom by upwelling which is one of the major mechanisms supporting the high productivity of coastal waters. YANAGI ( 1981) and IOI et al., (1981) discussed that upwelling especially due to wind blows is one of the most important factor for occurence of Red tides. So, the weather condition around Sea of Harima (hours of sunlight, precipitation, wind speed and wind direction) were compared during the summer (July-August ) of 1987 with those of 1985.
These data had been observed at Tokushima (see Fig. 1)
Comparison of data and its results
- The relationship between SST distribution and
its change due to the ebb and flow
The maximum extent of mixing area due to the ebb and flow is shown in Table 3. According to ariborne MSS, the front the maximum mixing area is located in 15km north and 22km south around the Naruto Channel.
This result means that mixing area due to the ebb and flow around Naruto Channel doesn't so much affect to the oceanic environment at the center of Sea of Harima.
- Difference of SST distribution during two
periods, the summer of 1987 (Red tides occurred ) and 1985 ( not
occurred)
Comparing SST distribution obtained from NOAA AVHRR data during
to periods, the summer of 1987 with 1985, the following were emphasized:
- Pattern of SST distribution during the summer
of 1987 was more homogeneous than that the 1985. During July of 1987,
minimum and maximum SST in Sea of Harima were approximately 24. c and
26. c respectively. And at the beginning of August, 26. c and 29. c.
At the end of August , 25. c and 28. c. Namely, the range of
difference was approximately from 2. c to 3. c. In 1985, minimum and
maximum SST were 24. c and 29. c and the range of difference was from
4. c to 5. c.
- During the summer of 1985, the clockwise
moving pattern of warm water body was observed, while it was not in
1987,
- An extent of mixing area around Naruto Channel
during the summer of 1987 was almost the same as 1985.
- Difference between weather condition during two periods, the summer of 1987 and 1985.
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