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ID 23451
本文ファイル
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別タイトル
Seasonal variation of solar radiation and underwater irradiance in the Seto Inland Sea
著者
遠藤 拓郎
松田 治
今林 博道
NDC
水産業
抄録(英)
The recent rapid eutrophication of the coastal seas of Japan has had a remarkable effect on the turbidity and transparency of the sea water, hence on the attenuation of underwater irradiance, which in turn influences the phytoplankton communities and primary productivity of the area.

The present study deals with the continuous three years observation of the total short-wave radiation, direct short-wave radiation, diffused short-wave radiation and photosynthetically active radiation of tlle Seto Inland Sea. Along with these observations, reflected short-wave radiation from the sea and transmitted short-wave radiation into the sea were determined. The availability of solar radiation for primary production, vertical distribution of spectral irradiance and attenuation coefficient were also discussed in relation to the optical water type of the region.

1. A typical seasonal variation in the monthly mean daily solar radiation (total short-wave radiation) was observed, with a maximal value of 17.0 MJ・m⁻² in July and minimal values of 7.4 to 7.5 MJ・m⁻² through November to January.

2. Seasonal variation of direct short-wave radiation was nearly identical to that of total short-wave radiation, with 9.3 MJ・m⁻² at maximum and 4.1MJ・m⁻² at minimum. Diffused short-wave radiation increased in June and decreased in January. The ratio of diffused short-wave radiation to total short-wave radiation ranged from 394000 62% with an average of 49%.

3. Seasonal variation of photosynthetically active radiation was very similar to that of direct short-wave radiation, with values of 7.3 MJ・m⁻² in July and of 3.3 MJ・m⁻² in December.

4. The albedo at the sea surface changed according to the incidence angle and surface conditions. Average daily values ranged from 2.9% on a fine summer day to 10% on an overcasted day in winter.

5. Underwater irradiance at a depth of 50cm varied widely according to such parameters as turbidity and the surface condition of the water. Observation revealed a remarkable decrease of irradiance in the upmost 50cm of the water column showing an inverse relationship between the intensity of underwater irradiance and turbidity.

6. From data on the vertical distribution of underwater irradiance, the attenuation coefficient for lux was calculated at 0.53 to 0.70, while that for quanta at 0.37 to 0.52.

7. As a result of spectral irradiance determination, a characteristic decrease in the longwave range was observed, especially in polluted areas. The optical water type of the region, as proposed by Jerlov, was classified into the Type 3 to Type 7 class for coastal waters.

8. From the simultaneous determination of net primary production by the phytoplankton community, average availability of total short-wave radiation and that of photosynthetically active radiation for primary production were estimated to be only 0.11% and 0.25%, respectively.
掲載誌名
広島大学生物生産学部紀要
22巻
2号
開始ページ
241
終了ページ
253
出版年月日
1983-12
出版者
広島大学生物生産学部
農林水産研究情報センター
ISSN
0387-7647
NCID
SelfDOI
言語
日本語
NII資源タイプ
紀要論文
広大資料タイプ
学内刊行物(紀要等)
DCMIタイプ
text
フォーマット
application/pdf
著者版フラグ
publisher
部局名
生物圏科学研究科
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