Variability of near-surface total suspended matter concentrations in the Dutch coastal zone of the North Sea: Climatological study on the suspended matter concentrations in the North Sea
Suijlen, J.M.; Duin, R.N.M. (2001). Variability of near-surface total suspended matter concentrations in the Dutch coastal zone of the North Sea: Climatological study on the suspended matter concentrations in the North Sea. Rapport RIKZ = Report RIKZ, 2001.150X. Rijkswaterstaat. Rijksinstituut voor Kust en Zee: The Hague. 85 pp.
Deel van: Rapport RIKZ = Report RIKZ. Rijksinstituut voor Kust en Zee (RIKZ): s-Gravenhage. ISSN 0927-3980, meer
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| Author keywords |
kustgebieden; mariene ecologie; troebelheid; waterkwaliteit |
| Auteurs | | Top |
- Suijlen, J.M.
- Duin, R.N.M.
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| Abstract |
Observed total suspended matter concentrations (TSM) in the upper layer of the water column in the Dutch coastal zone are statistically analysed. A correlation between TSM and seasonal wave climate is established. A winter and a summer season are defined on the basis of the wave climate. Winter and summer charts of the mean, median and mode of the TSM distribution are presented. The three-parameter lognormal distribution gives a good approximation of the observed probability distribution.
The investigated area is divided in a southern and a northern region, mainly on the basis of observed TSM ranges. The southern region contains the transects W, S and G (Fig. 1.1) and the northern region all transects north of Hook of Holland up to Terschelling. In each region also a near-coast part is defined (less than 6 km off-shore) and an open-sea part (at least 15 km from the coast). The underlying rationale for this subdivision is the strong cross-shore TSM gradient in the first 6 km from the coast and the very small cross-shore gradient at the larger distances. The 4 specially identified regions are called South<6, South>15, North<6, North>15. The mean concentrations in North>15 are about 3.7 mg/l in summer and 4.6 mg/l in winter, while those in South>15 are about 5 mg/l in summer and 9 mg/l in winter. The mean concentrations in North<6 are about 12 mg/l in summer and 30 mg/l in winter, while those in South<6 are about 18 mg/l in summer and 55 mg/l in winter. The ratio between the mean winter and summer concentrations equals about 2.5 and 1.3 in the regions North<6 and North>15, respectively. The ratio equals about 3 and 1.7 in the regions South<6 respectively South>15. The coefficient of variation roughly lies in the range 0.8- 1.2, with the smallest values in the near-coast part during winter. The ratio between the mean and mode (most frequently occurred concentration) is about 2.5 for all seasons and regions. The modes of TSM roughly fall in the range 0.9- 1.2 mg/l in North>15 during the summer period. During winter the modes in North>15 equal some 2-2.5 mg/l.
Probability graphs of TSM are presented for the winter and summer periods for each selected region. The role of TSM in the under-water light climate is discussed. All information is based on ship surveys that yielded no data during storms with wind forces > 8 Bft. Some preliminary results of recent in-situ measurements under such storm conditions show that TSM then may be strongly enhanced due to waves. |
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