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Uninodal, binodal, trinodal, and quadrinodal seic_65 map

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Uninodal (bimodal, trinodal and quadrinodal)

seiche oscillations

Seiches are standing waves in an enclosed or partially enclosed water body. Seiche oscillations in Lake Baikal are observed almost continuously throughout the whole year. Some characteristics of these oscillations were obtained from in-situ observations, laboratory experiments on a spatial hydraulic model and from appropriate theoretical calculations. The results of these studies have been published in the works (References). However, available information on Baikal seiches is scarce due to the difficulties of in-situ measurements and rather crude data on bottom topography. Sophisticated instrumental tools and advanced techniques for in-situ measurements were used to perform calculations of seiche oscillations in Lake Baikal based on a spectral difference model using specified bathymetric data obtained by researchers from Limnological Institute SB RAS. All these data are included in this atlas. The main aim of this study was to investigate solutions corresponding to oscillations with the periods of 277, 152, 84, 67, and 59 min, which were identified during in-situ observations.

The spectral difference model is based on the linearized system of equations for shallow water in the spherical coordinate system. Difference approximation is based on irregular triangular spatial mesh. The side length of the calculation mesh is 30 m near the shoreline and about 1 km for the rest of the model area. The numerical model includes solution of the eigenvalues problem. It allows the researchers to get a set of frequencies and corresponding forms of seiche oscillations.

The calculations were obtained taking into consideration the Earth’s rotation. Complex solutions were normalised in such a way that imaginary component was minimal, whereas true components of solutions for the rest of the model area were within the range of -10 to 10. The values in the nodes with the depth less than 10 m and in the nodes within the contour of Maloye More (Small Sea) were not taken into account. Spatial distribution of seiche oscillations with the periods of 276.96; 151.58; 84.25; and 67.38 min corresponds to uninodal, binodal, trinodal, and quadrinodal longitudinal seiche modes of Lake Baikal. The level distribution along the centreline is shown for the enumerated modes in Figure. It should be noted that it is necessary to use other approaches for specification of solutions in shallow areas of Lake Baikal, such as Mukhor and Proval Bays and Cherkalovsky and Posolsk Sors, where the bottom friction is likely to play a significant role. The results for the first mode are consistent with the data on distribution of seiche oscillation height along the Baikal length in [Sudolsky, 1991, Fig. 5.2], in which the data on calculations and survey results from the spatial hydraulic model are compared.

Amplitudes of seiche oscillations in Lake Baikal and their seasonal variability were analysed from the data obtained at 3 stations located in the southern basin of the lake. Well-defined maxima for the oscillations with the periods of 277, 152, 84, and 67 min are observed within the range of density spectrum derived from the annual level record. No significant differences were recorded between the amplitudes for a uninodal seiche and amplitudes during the rest of the year when the lake is covered with ice and protected from wind. It was established that a seiche with the period of 67 min is observed in different seasons of the year. At three stations, level changes for the oscillation with the 277 min period differ in significantly. For the 152 min period they have slight differences, and for the 84 and 67 min periods they are similar only at those sites with relatively high amplitudes of oscillations. This is attributed to the effect of wind and atmospheric pressure. Measured and calculated periods for the first four seiche modes are given in Table.

References

Arsenyeva, N. M., Davydov, L. K., Dubrovina, L. N., & Konkina, N. G. (1963). Seiches in lakes of the USSR. Leningrad: LSU Publishing. p 184.

Verbolov, V. I. (1970). On Baikal seiches. In Seiches in lakes: Surface and internal. Leningrad: Nauka. p 50-52.

Solovyev, V. N. (1925). Method of models and its application in seiche survey at Lake Baikal. News of the Institute of Biology and Geography, 2. p 9-26.

Solovyev, V. N., Shostakovich, V. B. (1926). Seiches in Lake Baikal. Proceedings of Magnetic and Meteorological Observatory, 1.

Sudolsky, A. S. (1991). Dynamic phenomena in water bodies. Leningrad: Hydrometeoizdat. p 263 p.

Sudolsky, A. S. (1968) Laboratory experiments and calculations of Baikal seiches. Proceedings of GGI, 155. p 109-123.

Timofeev, V. Y., Ardyukov, D. G., Granin, N. G., Zhdanov, A. A., Kucher, K. M., Boiko, E. V., & Timofeev, A.V.  (2010). Deformation of ice cover, tidal and true level fluctuations of Lake Baikal. Phys. Mesomech: Special Issue, 13, p 58-71.

Timofeev, V. Y., Granin, N. G., Ardyukov, D. G., Zhdanov, A. A., Kucher, K. M., & Ducarme, B. (2009). Tidal and seiche signals on Baikal Lake level. Bulletin of Inf. MareesTerrestres, 145. p 11635—11658.

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