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Operational forecasts during the construction of the Fixed Link across the Öresund
Operational Oceanography: hnplementation at the European and Regional Scales edited by N.C. Flemming, S. Vallerga, N. Pinardi, H.W.A. Behrens, G. Manzella, D. Prandle, J.H. Stel 2002 Elsevier Science B.V.
149
O p e r a t i o n a l f o r e c a s t s d u r i n g the c o n s t r u c t i o n o f the F i x e d L i n k a c r o s s the Oresund Lennart Funkquist Swedish meteorological and Hydrological Institute S-602 36 Norrk6ping, Sweden lfunkqui @ smhi.se
The construction of the fixed link across the Oresund started in 1996 and will be finished in summer 2000. The link is a combination of a tunnel, an artificial island and a high bridge. The construction work at levels up to 200 m and the precise castings of both tunnel elements and foundations, bridge piers and pylons for the bridge mean sensitive operations at sea, where both the weather and the oceanographic conditions play an important role. SMHI (Swedish Meteorological and Hydrological Institute) together with DMI (Danish Meteorological Institute) supply the construction companies with daily forecasts.
1.
INTRODUCTION
The whole length of the fixed link across the Oresund is 15.4 kin, subdivided into a tunnel of 3.5 km, an artificial island of 4.1 km and a bridge of 7.8 kin. The bridge comprises an elevated bridge across the Flinte Channel and two approach bridges. The two-level high bridge has a main span of 490 m and a free sailing height of 57 m. The eastern pair of pylon pairs for the high bridge is now the highest building in Sweden (204 m). For an overview picture, see Figurel. As much of the construction work takes place at levels up to 200 m, detailed forecasts of wind and temperature profiles as well as visibility are of much value during the daily work. For both the preparations and the casting of the tunnel elements, foundations, bridge piers and pylons, forecasts and real-time data of oceanographic parameters like waves, currents and water level are crucial for successful operations. SMHI supplies the construction companies with both real-time data as well as oceanographic and meteorological forecasts twice a day.
2.
REAL-TIME MEASUREMENTS
Real-time measurements are important especially for sensitive operations like the casting of tunnel elements and pylons. Besides meteorological measurements of wind, temperature and precipitation, SMHI has an oceanographic monitoring system comprising the following elements:
150 9 9 9 9
Temperature and salinity profiles are transmitted with a combination of cable from the T/C string to a buoy and then by Inmarsat C. Waves are measured with a Datawell accelerometer buoy and the data are transmitted to the shore via radio-link. Currents are measured with a RD Acoustics Doppler profiler and the data are transmitted by cable to the Flinten Lighthouse and further to the shore by radio-link Water level is measured with an acoustic measure and transmitted by telecommunication
Figure 1. A schematic picture of the southem part of the 0resund and the fixed link.
3.
OPERATIONAL MODELS
For most of today's operations at sea, there is a need for information of both meteorological and oceanographic conditions. SMHI is in a unique position as being the governmental authority for operational forecasts of meteorology, oceanography and hydrology. For the Fixed Link across the Oresund, SMHI delivers forecasts from the ECMWF (European Centre for Medium-Range Weather Forecasting) model, the HIRLAM (High Resolution Limited Area Model) model, the HYPAS (Hybrid Parametric Shallow sea wave model) wave model and the HIROMB (High Resolution Operational Model for the Baltic Sea) ocean model. Although the wind up to 200 m height is the main limiting factor for the construction of the high-level bridge, both air temperature and visibility may disturb the work. The meteorological forecasts are taken from the HIRLAM (HIRLAM, 1993) model with a horizontal resolution of 22 km and 31 vertical levels. The forecast length is maximum 36 hours but a 48-hour forecast is also run with a 44 km resolution model. Longer forecasts (up to 5 or six days) are extracted from the ECMWF model. Although the wave conditions in the Oresund are rather modest compared to normal offshore conditions, wave forecasts are still of great value since much of the construction deals
151 with the careful casting and towing of big elements. The wave forecasts are valid for up to 48 hours and are done with a nested version of the 2 "d generation wave model HYPAS. A large grid with 22 km resolution covers the North Atlantic and the North Sea. This is coupled to an 11 km grid for the Skagerrak/Baltic Sea region. This grid is further resolved with a 5.5 km grid for the Kattegat/Arkona area and finally a 550 m grid for the southern part of the 0resund. Forecasts are given mainly for significant wave height and mean wave period. Figure 2 shows an example of a forecast of significant wave height for the construction area.
Figure 2. An example of a forecast of significant wave height for the southern part of the Oresund. The Oresund is one of the main channels between the Baltic Sea and the North Sea. There is a large variation in transport through the Oresund on the time scale of days related to the meteorological meso-scale activity, i.e. passing of cyclones. The maximum current velocity is about 2 m/s, which is of enough strength to sometimes stop part of the construction work. Although the ocean model, HIROMB (Funkquist and Kleine, 1999), has a relatively coarse resolution (3 nautical miles), experience has shown that its forecasts of transport are of enough quality to be used in the planning of the work.
4.
MARINE FORECASTING SMHI has since the start of the pre-investigation and during the construction delivered detailed forecasts twice a day. The service is operating 24 hours a day and also includes information on the real-time conditions, which affect the construction work. The marine forecasting department is a special section at SMHI in close contact with but separated from the meteorological department.
152
Its main customers are 9 9 9 9 9 9
Shipping companies and ferry lines Harbours/stevedoring Construction companies Coast Guard Towing companies Ice service
ACKNOWLEDGMENTS Information on real-time measurements and operational marine forecasting has been provided by Kjell Wickstr6m and Torbj6rn Grafstr6m, SMHI.
REFERENCES L. Funkquist and E. Kleine, 1999. HIROMB, an Introduction to an Operational Baroclinic Model for the North Sea and Baltic Sea. Manuscript available from SMHI, S 60176 Norrk6ping, Sweden. HIRLAM, editor. Nils Gustafsson, 1993. The HIRLAM 2 Final Report. HIRLAM Tech Rept. 9, Available from SMHI, S-60176 Norrk6ping, Sweden
149
O p e r a t i o n a l f o r e c a s t s d u r i n g the c o n s t r u c t i o n o f the F i x e d L i n k a c r o s s the Oresund Lennart Funkquist Swedish meteorological and Hydrological Institute S-602 36 Norrk6ping, Sweden lfunkqui @ smhi.se
The construction of the fixed link across the Oresund started in 1996 and will be finished in summer 2000. The link is a combination of a tunnel, an artificial island and a high bridge. The construction work at levels up to 200 m and the precise castings of both tunnel elements and foundations, bridge piers and pylons for the bridge mean sensitive operations at sea, where both the weather and the oceanographic conditions play an important role. SMHI (Swedish Meteorological and Hydrological Institute) together with DMI (Danish Meteorological Institute) supply the construction companies with daily forecasts.
1.
INTRODUCTION
The whole length of the fixed link across the Oresund is 15.4 kin, subdivided into a tunnel of 3.5 km, an artificial island of 4.1 km and a bridge of 7.8 kin. The bridge comprises an elevated bridge across the Flinte Channel and two approach bridges. The two-level high bridge has a main span of 490 m and a free sailing height of 57 m. The eastern pair of pylon pairs for the high bridge is now the highest building in Sweden (204 m). For an overview picture, see Figurel. As much of the construction work takes place at levels up to 200 m, detailed forecasts of wind and temperature profiles as well as visibility are of much value during the daily work. For both the preparations and the casting of the tunnel elements, foundations, bridge piers and pylons, forecasts and real-time data of oceanographic parameters like waves, currents and water level are crucial for successful operations. SMHI supplies the construction companies with both real-time data as well as oceanographic and meteorological forecasts twice a day.
2.
REAL-TIME MEASUREMENTS
Real-time measurements are important especially for sensitive operations like the casting of tunnel elements and pylons. Besides meteorological measurements of wind, temperature and precipitation, SMHI has an oceanographic monitoring system comprising the following elements:
150 9 9 9 9
Temperature and salinity profiles are transmitted with a combination of cable from the T/C string to a buoy and then by Inmarsat C. Waves are measured with a Datawell accelerometer buoy and the data are transmitted to the shore via radio-link. Currents are measured with a RD Acoustics Doppler profiler and the data are transmitted by cable to the Flinten Lighthouse and further to the shore by radio-link Water level is measured with an acoustic measure and transmitted by telecommunication
Figure 1. A schematic picture of the southem part of the 0resund and the fixed link.
3.
OPERATIONAL MODELS
For most of today's operations at sea, there is a need for information of both meteorological and oceanographic conditions. SMHI is in a unique position as being the governmental authority for operational forecasts of meteorology, oceanography and hydrology. For the Fixed Link across the Oresund, SMHI delivers forecasts from the ECMWF (European Centre for Medium-Range Weather Forecasting) model, the HIRLAM (High Resolution Limited Area Model) model, the HYPAS (Hybrid Parametric Shallow sea wave model) wave model and the HIROMB (High Resolution Operational Model for the Baltic Sea) ocean model. Although the wind up to 200 m height is the main limiting factor for the construction of the high-level bridge, both air temperature and visibility may disturb the work. The meteorological forecasts are taken from the HIRLAM (HIRLAM, 1993) model with a horizontal resolution of 22 km and 31 vertical levels. The forecast length is maximum 36 hours but a 48-hour forecast is also run with a 44 km resolution model. Longer forecasts (up to 5 or six days) are extracted from the ECMWF model. Although the wave conditions in the Oresund are rather modest compared to normal offshore conditions, wave forecasts are still of great value since much of the construction deals
151 with the careful casting and towing of big elements. The wave forecasts are valid for up to 48 hours and are done with a nested version of the 2 "d generation wave model HYPAS. A large grid with 22 km resolution covers the North Atlantic and the North Sea. This is coupled to an 11 km grid for the Skagerrak/Baltic Sea region. This grid is further resolved with a 5.5 km grid for the Kattegat/Arkona area and finally a 550 m grid for the southern part of the 0resund. Forecasts are given mainly for significant wave height and mean wave period. Figure 2 shows an example of a forecast of significant wave height for the construction area.
Figure 2. An example of a forecast of significant wave height for the southern part of the Oresund. The Oresund is one of the main channels between the Baltic Sea and the North Sea. There is a large variation in transport through the Oresund on the time scale of days related to the meteorological meso-scale activity, i.e. passing of cyclones. The maximum current velocity is about 2 m/s, which is of enough strength to sometimes stop part of the construction work. Although the ocean model, HIROMB (Funkquist and Kleine, 1999), has a relatively coarse resolution (3 nautical miles), experience has shown that its forecasts of transport are of enough quality to be used in the planning of the work.
4.
MARINE FORECASTING SMHI has since the start of the pre-investigation and during the construction delivered detailed forecasts twice a day. The service is operating 24 hours a day and also includes information on the real-time conditions, which affect the construction work. The marine forecasting department is a special section at SMHI in close contact with but separated from the meteorological department.
152
Its main customers are 9 9 9 9 9 9
Shipping companies and ferry lines Harbours/stevedoring Construction companies Coast Guard Towing companies Ice service
ACKNOWLEDGMENTS Information on real-time measurements and operational marine forecasting has been provided by Kjell Wickstr6m and Torbj6rn Grafstr6m, SMHI.
REFERENCES L. Funkquist and E. Kleine, 1999. HIROMB, an Introduction to an Operational Baroclinic Model for the North Sea and Baltic Sea. Manuscript available from SMHI, S 60176 Norrk6ping, Sweden. HIRLAM, editor. Nils Gustafsson, 1993. The HIRLAM 2 Final Report. HIRLAM Tech Rept. 9, Available from SMHI, S-60176 Norrk6ping, Sweden