Fourth Study Conference on BALTEX Scala Cinema Gudhjem

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- 92 - On Variability of the Riverine Waters in the Gulf of Gdansk - a Model <strong>Study</strong> Andrzej Jankowski Institute of Oceanology of PAS., Powstańców Warszawy 55, 81-712 Sopot, Poland, e-mail: jankowsk@iopan.gda.pl 1. Introduction A three−dimensional baroclinic σ-coordinate model was used to investigate the development and evolution of buoyant river plumes in the Gulf of Gdansk (Gdansk Basin). Situated in the southern part of the Gdansk Basin, the Gulf of Gdansk, is one of the Baltic's open gulfs. Its hydrological regime is formed by atmospheric forcing and, due to wide and deep connection with the open sea, under influence of the Baltic proper (Majewski 1990). Its surface waters are influenced by riverine inflows among which the greater significance has those of the Vistula River (with mean annual discharge about 1000 m3/s Cyberski 1997), the biggest river in the region. The mixed river waters can be observed at the open boundary of the Gulf of Gdansk or even futher after the strong flood events. The inflow of riverine waters substantially modifies the environmental conditions in the surface water of the Gulf by reducing its salinity as well as contaminating it with their pollution load (Andrulewicz 1996, Cyberska and Krzyminski 1988, 1996). The purpose of this study is to obtain more detailed information on fate of riverine water as it mixes and moves around with the currents and winds in the Gulf of Gdansk and to test the capabilities of the model to simulate the characteristic features of the spreading of the riverine waters during summer flood event. 2. Model The model is based on the Princeton Ocean Model (POM) - code of Blumberg and Mellor 1987 adapted to the Baltic Sea conditions (Jankowski 2002a). POM is based on a standard formulation of the conservation equations for momentum and mass, utilizing the hydrostatic and the Boussinesq approximation. The model uses Smagorinsky (1963) parameterization for the horizontal mixing (turbulent exchange). To calculate the vertical eddy viscosity and diffusion coefficients a second turbulence closure scheme (Mellor and Yamada 1974, 1982) is applied. The model domain comprises the whole Baltic Sea with the Gulf of Bothnia, the Gulf of Finland and the Gulf of Riga as well as the Danish Straits and Kattegat and Skagerrak. At the open boundary in the Skagerrak simplified radiation-type boundary conditions are applied. The bottom topography of the Baltic Sea used in the model is based on data from Seifert and Kayser (1995). A “C” numerical grid (Mesinger and Arakawa 1976) is applied. With a horizontal resolution of ≈ 5 km and with 24 σ-levels in vertical, the model enables variability as well as mesoscale features of the order of 10 km of currents and thermohaline fields in the Baltic Sea to be investigated. To date, the model has been investigated to simulate major features of the coastal area of the Southern Baltic (Jankowski, 2002a, 2002b). 3. Model experiments The climatological forcings were coupled to the model by means of the so-called method of ’relaxation towards climatology’ ( cf. Lehmann 1995). Wind field is estimated from atmospheric surface pressure charts and surface heat fluxes at the sea surface are calculated with standard bulk formulae. In order to simulate the characteristic features of wind- and river inflow-induced variability of hydrodynamic conditions in the Gdansk Basin, the prognostic hindcast calculations were performed for summer period of 1980 (summer flood event in the Vistula catchment). Model runs, starting with climatological montly means of temperature and salinity were carried out for the period of 1 st July to 31 st August 1980. For this simulation the model was forced by realistic forcing estimated on 3-hourly atmospheric data (pressure, air temperature, relative humidity and the wind - field) taken from (BED, 2000) and by climatological forcings. A comparison of computed and measured temperature and salinity shows that the model reproduces the vertical structure of seawater temperature and salinity in a good agreement to the in situ observations. Besides the realistic meteorological forcing the spatially uniform winds from 8 directions and without wind were also considered. The winds from 8 directions: SE, S, SW, W, NW, N, NE and E, of constant speed over the whole Baltic area. The wind stress was assumed to be in a range from 0.025 to 0.1 N/m2. 4. Results and comments The sea water salinity was used as a natural tracer for visualization of spreading of riverine waters in the Gulf of Gdansk. The numerical experiments visualize the patterns of weak saline surface water (riverine plume) propagation on their way from the Vistula mouth toward the open boundary of the Gulf of Gdansk. The results show that local hydrodynamics near the river mouth, and consequently the spreading of the river plume, are highly dependent on the driving river discharge and wind field characteristics. In the absence of wind forcing the modeled river plumes typically consist of an offshore bulge and a alongshore currents in the counterclockwise direction. In the presence of wind forcing the favorable conditions for offshore removal of coastal low-salinity waters include favorable wind stress and circulation pattern highly dependent on open sea hydrodynamic conditions. The results of simulations with space uniform winds showed that the surface water plume can be particularly sensitive to the wind stress because it is thin. Its extent is influenced by the wind stress and varied depending on the orientation of the wind stress. The values of area of mixing zone (salinity < 7 PSU) vary from 1100-1200 km˛ (wind from E and NE) to 400-500 km2 (winds from W and SW). Under stronger winds the area of mixing zone decrease almost twice. These findings and general response of surface waters to river run-off and winds are in agreement with in situ measurements(e.g.
Cyberska 1989, Cyberska and Krzyminski 1988) as well as with theoretical and numerical investigations (cf. Fennel and Mutzke 1997). It is believed that the results of numerical simulation help to understand the distribution and temporally changes of the surface waters as well as the hydrodynamics of the Vistula river plume during the flood events in summer period. References Andrulewicz G., Regional characteristics of the Gdansk Basin, [in:] An Assesment of the Effects of Pollution in the Polish Marine Area of the Baltic Sea, 1989-1993, Oceanoogical. Studies, 25, No. 1-2, 11-16, 1996 BED, Atmospheric inputs, [in:] The BED database, http://data.ecology.su.se//Models//bedcontent.htm, 2000 Blumberg, A. F., Mellor G. L., A description of a threedimensional coastal ocean circulation model, [in:] Three-Dimensional Coastal ocean Models, edited by N. Heaps, 208 pp., American Geophysical Union , 1987 Bock K.-H. Monatskarten des Salzgehaltes der Ostsee, dargestellt fuer verschiedene Tiefenhorizonte. Dt. hydrogr. Z., Erg.-H. R. B., No.12, Hamburg. 148 pp. , 1971 Cyberska B., Krzyminski W.,Extention of the Vistula Water in the Gulf of Gdansk, Proc. 16th CBO, Kiel, vol. 1, 290-304, 1988 Cyberska B., Thermohaline conditions in the Gdansk Basin, Oceanological Studies, 25, No. 1-2, 17-39, 1996 Cyberski J., Riverine water outflow into the Gulf of Gdansk, Oceanological Studies, 26, No. 4, 1997, 65-75, 1997 Fennel W., Mutzke A., The initial evolution of a buoyant plume, J. Mar. Sys., 12 (1-4), 53-68, 1997 Jankowski A., Application of the σ-coordinate baroclinic model to the Baltic Sea, Oceanologia, 44, No. 1, 59-80, 2002a Jankowski A., Variability of coastal water hydrodynamics in the Southern Baltic hindcast modelling of an upwelling event along the Polish coast, Oceanologia, 44, No. 4, 395-418, 2002b Lehmann A., A three-dimensional baroclinic eddyresolving model of the Baltic Sea., Tellus, vol. 47A, No. 5:2, 1013 – 1031, 1995 Lenz W., Monatskarten der Temperatur der Ostsee, dargestellt fuer verschiedene Tiefenhorizonte. Dt. hydrogr. Z., Erg.-H. R. B., No.11, Hamburg, 148 pp. , 1971 Majewski A. (ed.), , The Gulf of Gdansk, Wydawnictwa Geologiczne, Warszawa, 1990, pp. 501 (in Polish) Mesinger F., Arakawa A., Numerical models used in atmospheric models, GARP Publications Series, No. 17, 1, WMO - ICSU, 64 pp., 1976 Mellor G. L., Yamada, T., A hierarchy of turbulence closure models for planetary boundary layers, J. Atmos. Sci., 13, 1791-1806 , 1974 Mellor G. L., Yamada T., 1982, Development of a turbulent closure model for geophysical fluid problems, Rev. Geophys., 20, 851-875 , 1982 - 93 - Oey, L.-Y., Chen P., A model simulation of circulation in the northeast Atlantic shelves and seas, J. Geophys. Res., 97, 20087-20115 , 1992 Seifert T., Kayser, B., A high resolution spherical grid topography of the Baltic Sea, Meereswissenschaftliche Berichte, No. 9, Institut für Ostseeforschung, Warnemünde, 72-88., 1995
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Fourth Stu
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Preface The 4 th Study</str
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- I - Table of Abstracts Title Auth
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- III - Sensitivity in Calculation
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- V - Parameter Estimation of the S
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- VII - The Realism of the ECHAM5.2
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Adam, W. K. .......................
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- 1 - Activities of the GEWEX Hydro
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eference site archive (Cabauw, Neth
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- 5 - Remote Sensing of Atmospheric
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minute averages around the satellit
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- 9 - Precipitation Type Statistics
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- 11 - Assimilation of New Land Sur
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Multichannel Microwave Radiometer f
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output has been processed in an equ
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height dependence of the Z-R-relati
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- 19 - CERES and Surface Radiation
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- 21 - Coastal Wind Mapping from Sa
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- 23 - Clouds and Water Vapor over
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- 25 - Broadband Cloud Albedo from
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- 27 - Observation of Clouds and Wa
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shows a ground-track of the vessel
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- 31 - Determination and Comparison
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- 33 - Spatial Variability of Snow
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- 35 - EVA-GRIPS: Regional Evaporat
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- 37 - LITFASS-2003 - A Land Surfac
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-39- Calibrated Surface Temperature
Page 57 and 58: - 41 - The Marine Boundary Layer -
Page 59 and 60: - 43 - Characteristics of the Atmos
Page 61 and 62: Figure 2. Surface stress from two d
Page 63 and 64: During the experiment the water was
Page 65 and 66: While the number of smallest drops
Page 67 and 68: SCANDIA will not be supported any l
Page 69 and 70: - 53 - Relationships Between Precip
Page 71 and 72: - 55 - Analysis of the Role of Atmo
Page 73 and 74: - 57 - Meteorological Peculiarities
Page 75 and 76: Baltic Sea Inflow Events Jan Piechu
Page 77 and 78: - 61 - The Different Baltic Inflows
Page 79 and 80: - 63 - Observations of Turbulent Ki
Page 81 and 82: - 65 - The Influence of Synoptic Si
Page 83 and 84: -67- Improved Method for the Determ
Page 85 and 86: -69- The Helicopter-Borne Turbulenc
Page 87 and 88: - 71 - CEOP Reference Site Data fro
Page 89 and 90: - 73 - The BALTEX Hydrological Data
Page 91 and 92: - 75 - Hydrological and Hydrochemic
Page 93 and 94: -77- Sea-level Monitoring at MARNET
Page 95 and 96: 1 0.8 0.6 0.4 0.2 GO(CLD-M) ERA40 S
Page 97 and 98: Figure 2. Monhly mean values of lat
Page 99 and 100: In the case of an ideal fit, the co
Page 101 and 102: - 85 - Influence of Atmospheric For
Page 103 and 104: The largest inter-annual variabilit
Page 105 and 106: References Andrejev, O, Sokolov, A.
Page 107: On the other hand, if the stratific
Page 111 and 112: - 95 - Continental-Scale Water-Bala
Page 113 and 114: - 97 - ICTS (Inter-CSE Transferabil
Page 115 and 116: The subsurface flow calculation is
Page 117 and 118: functions only data with higher qua
Page 119 and 120: - 103 - Modelling the Impact of Ine
Page 121 and 122: - 105 - Objective Calibration of th
Page 123 and 124: - 107 - Validation of Boundary Laye
Page 125 and 126: - 109 - Simulated Dynamical Process
Page 127 and 128: spreads along isobaths (fig.2). As
Page 129 and 130: than the precipitation pattern of J
Page 131 and 132: Figure 2. Long-term variability in
Page 133 and 134: obvious from temperature charts. Ho
Page 135 and 136: shortening of the winter seasons by
Page 137 and 138: Maximum 5 day precipitation (mm) Nu
Page 139 and 140: scale parameters the correlation be
Page 141 and 142: similar: the locations of main mini
Page 143 and 144: - 127 - Storminess on the Western C
Page 145 and 146: - 129 - Trends in Wind Speed over t
Page 147 and 148: - 131 - Wind Energy Prognoses for t
Page 149 and 150: - 133 - Detection of Climate Change
Page 151 and 152: Figure 3. Cross section of salinity
Page 153 and 154: of 35 m/s up to 3 hours. Data on wi
Page 155 and 156: Figure 2. Time series of Mean Sea L
Page 157 and 158: - 141 - Calculation and Forecast of
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- 143 - An Overview of Long-Term Ti
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- 145 - Baltic Sea Saltwater Inflow
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- 147 - Significance of Feedback in
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Lindström, G., Johansson, B., Pers
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- 151 - Air-Sea Fluxes Including Mo
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- 153 - The Realism of the ECHAM5.2
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- 155 - Figure 3. Accumulated total
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Figure 2. Example for Fourier decom
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Figure1. Modeled percent volume cha
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conditions even more challenging th
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surface heat fluxes close to zero.
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- 165 - Figure 1. Modeled seasonal
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- 167 - Present-Day and Future Prec
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- 169 - Extreme Precipitation on a
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at the stations Pärnu (Estonia) an
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6. Results There are many possible
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and vegetation, and to derive the h
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The structure of water bodies cadas
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Figure 1. The area of Gdańsk subje
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- 181 - Climate and Water Resources
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- 183 - Generating Synthetic Daily
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The evapotranspiration is affected
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Model parameters and coefficients:
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3. Hydrodynamic model of nutrient l
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No. 15: Minutes of 8 th Meeting of
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Fourth Study Conference on BALTEX Scala Cinema Gudhjem

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