TP 10820 E
WIND AND WAVE CLIMATE ATLAS
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VOLUME II - THE GULF OF ST. LAWRENCE
MacLaren Plansearch (1991) Limited
Suite 200, Park Lane Terraces
5657 Spring Garden Road
Halifax, Nova Scotia
Transportation Development Centre
Policy and Coordination Group
"The contents of this report reflect the views of the authors and not necessarily the official views or opinions of the Transportation Development Centre, Policy and Coordination Group, of Transport Canada."
The sponsorship and technical support given in the preparation of this work is acknowledged as follows:
- The sponsorship and technical support given in the preparation of this work is acknowledged as follows:
- Transport Canada - Transportation Development Centre
- Transport Canada - Canadian Coast Guard-Ship Safety
- Energy, Mines and - Program for Energy R & D
- Resources Canada
- Environment Canada - Canadian Climate Centre
- Fisheries and Ocean - Marine Environment Data Service
- Lloyd's Register of Shipping
Offshore exploration and shipping activities are affected by the climate conditions in the area. With an accurate description of the operating environment, ships and other marine structures can operate safely in these areas. This study was initiated by the Transportation Development Centre (TDC) on behalf of the Canadian Coast Guard, Transport Canada to develop a wind and wave climate atlas for the east coast of Canada, Gulf of St. Lawrence, and the Great lakes. The objective of this project is to collect, consolidate, and present the existing environmental data in a format which could be used to assess the strength and operational requirements of vessels and other marine structures for operation in these regions.
The atlas is divided into three volumes describing the following regions:
Volume I - The East Coast of Canada;
Volume II - The Gulf of St. Lawrence
Volume III - The Great Lakes.
Each region was divided into a number of subareas (or sites) to represent the various conditions within the region. The division of the subareas was based on the availability of data within the region, shipping lanes and fishing grounds, and the meteorological conditions within each sub area.
This volume presents the Gulf of St. Lawrence. In this volume, the region was divided into five sub areas as shown in Figure 1. These subareas also followed closely Environment Canada's marine forecasting areas.
An extensive database was compiled from all relevant data sources, which included both measured/observed data and hindcast studies. An extensive review and evaluation of these data sources, user requirements, analysis techniques, etc. is provided in a separate report (Phase I Report, MacLaren Plansearch Limited, 1989, Transport Canada publication # TP 10867E).
- North-East Gulf
- Central Gulf
- Cabot Strait
The data sets used to produce the climatological statistics presented herein were:
"ship-of-opportunity" wind data from COADS (Comprehensive Ocean-Atmospheric Data Set) and real-time buoy and rig data sets archived at Atmospheric Environment Service (AES), Downsview, Ontario, covering a time period from 1957-1988.
Waverider and The U.S. National Oceanic and Atmospheric Administration (NOAA) wave buoy data archived at Marine Environmental Data Service (MEDS), Ottawa, covering a time period from 1970- 1989.
Three-year ODGP wind/wave hindcast database, archived at MEDS, Ottawa, and at MacLaren Plansearch, Halifax, covering a time period from 1983-1986. This continuous three-year database provides a reliable description of the full directional wave spectra for the east coast and the Gulf of St. Lawrence, see Eid et al. (1989).
Extreme storm hindcasts using the ODGP wave model. The top 30 storms in each area were used to estimate the design values for a given recurrence interval or return period (e.g. 100 year or probability of exceedance of 0.01). See Canadian Climate Centre (1991) and Swail et al. (1989).
For the Gulf of St. Lawrence, a special version of the ODGP which includes Capes and Islands (CAIPS) was used to resolve the large islands effect.
For each sub-area, the maximum wind and wave values during three-hour time intervals were selected from each data set. The "ship-of-opportunity" wind data were used for providing the wind statistics, and the waverider/NOAA buoy wave data were used for providing the wave statistics. The three year ODGP hindcast data were used when data from the other two data sets were insufficient. Also for duration statistics, (e.g. persistence analysis) a continuous time series of the parameters considered is needed. The ODGP data set was used for this purpose and also for providing wave direction statistics.
Note: It should be emphasized that the ODGP model hindcasts used-- in this atlas represent deep water wave conditions, and therefore must be treated as such. Shallow water effects should be considered locally.
The three-hourly marine wind data were used in the analysis presented in this atlas. It presents one-hour mean winds. Following conversion factors (U.K. Department of Energy, 1977) may be used to convert wind speed to other averaging periods.
In the ship-of-opportunity data set, the anemometer height of the measured wind speeds varies with each ship, buoy or rig. For some ship call signs, the anemometer height was known and was used to adjust the wind speed to a height of 19.5 m (65 ft.) above mean sea level using the marine planetary boundary layer approach (Cardone, 1978). Most of the anemometer heights of the rigs and buoys were known and were used to adjust the wind to a standard 19.5 m level. However, not all ship anemometer heights were known. Since the average height of ship anemometers is approximately 20 m, most ship-reported wind speeds should be compatible with the adjusted wind speeds. The ODGP hindcast winds were determined for 19.5 m height.
All wind speed statistics were compiled using the "ship-of- opportunity" data except for the persistence analysis. Since the persistence analysis requires a continuous time series of data with no gaps, the "ship of opportunity" data were not appropriate. Therefore, the ODGP data base was used for this purpose.
Waverider and NOAA buoy data were used for non-directional wave spectral analysis and significant wave height and wave period statistics in areas where a sufficient number of measurements were available. The three.year ODGP hindcast data base was used for the remaining areas, and for directional statistics such as wave roses and percent frequency of occurrence by direction tables.
The following data bases were used for the wave statistics:
|Gulf of St. Lawrence||Non-directional Statistics||Directional Statistics|
where WR is measured wave data, and ODGP is the ODGP model hindcast data. It should be noted that due to the use of these two different data sources, slightly different wave statistics would be expected for a given sub-area (e.g. Pages 3-12 to 14 and 3-16).
Extreme value statistics were calculated by using the method of moments (MOM) to fit a Gumbel distribution to peak storm wind and wave values. The criteria for selecting wind storms were winds surpassing a threshold of 35 knots for a minimum duration of 12 hours and storm peaks at least 24 hours apart. From this, a preliminary list of potential storms was obtained and verified. The peak wind speed for each storm was then identified and used in the extreme analysis.
The significant wave height extreme statistics were based on the hind cast of the top severe wave-generating storms in the study area using the ODGP model. See Canadian Climate Centre (1991).
The presence of sea ice in the Gulf of St. Lawrence during January through April affects the wave statistics, since little or no data are available during this period. This is noted on the affected items. It should be noted that the actual ice edge was incorporated into the ODGP model hindcasts.
Many marine engineering applications require knowledge of the shape of the wave spectra. The analysis used in this atlas is based on the six-parameter model of Ochi and Hubble (1976). To generate the representative spectrum for a given sea-state value, the model function was fitted to the measured or hindcast data. Statistical analysis of the fitted parameters leads to a family of spectra, i.e. most probable spectrum and a set of 95% confidence spectra. Six sea-state classes were considered: Hs=0.5-2 m, 2-3 m, 3-4 m, 4-5 m, 5- 6 m, and greater than 6 m.
LIST OF PARAMETERS & ANALYSIS PERFORMED
The following is a list of statistics provided for area xx (and the corresponding page number):
|Wind Speed Statistics|
|Annual Percentage Occurrence||xx-1|
|Annual Percentage Exceeding||xx-1|
|Annual Frequency of Occurrence by Direction (Wind Rose)||xx-1|
|Annual Percentage Exceeding for Given Time Durations (Persistence)||xx-1|
|Monthly Frequency of Occurrence by Direction (Wind Rose)||xx-2,3|
|Monthly Percentage Occurrence||xx-4,5|
|Monthly Percentage Exceeding||xx-6,7|
|Monthly Statistics (mean, maximum, minimum, 95% limits, etc.)||xx-8|
|Annual Percent Frequency of Occurrence by Direction (Table)||xx-8|
|Significant Wave Height Statistics|
|Annual Percentage Occurrence||xx-9|
|Annual Percentage Exceeding||xx-10|
|Annual Frequency of Occurrence by Direction (Wave Rose)||xx-9|
|Annual Percentage Exceeding for Given||xx-10|
|Time Durations (Persistence)||xx-10|
|Monthly Frequency of Occurrence by Direction (Wave Rose)||xx-11,12|
|Monthly Percentage Occurrence||xx-13,14|
|Monthly Percentage Exceeding||xx-15,16|
|Monthly Statistics (mean, maximum, minimum, 95% limits, etc.)||xx-19|
|Annual Percent Frequency of Occurence by Direction (Table)||xx-19|
|Most Probable Spectra||xx-21|
|Wave Spectral Coefficients (Table)||xx-22|
|Wave Peak Period Statistics|
|Annual Percentage Occurrence||xx-9|
|Annual Percentage Exceeding for Given Time Durations (Persistence)||xx-10|
|Monthly Percentage Occurrence||xx-17,18|
|Joint Probability Statistics|
|Annual Occurrence of Significant Wave Height and Wind Speed||xx-20|
|Annual Occurrence of Significant Wave Height and Peak Period||xx-20|
Cardone, V.J., 1978. Specifications and Prediction of the Vector Wind on the United States Continental Shelf for Applications to Oil Slick Trajectory Forecast Program. Final Report, Contract T-35430, NOAA, U.S. Department of Commerce, Silver Spring, Maryland.
Eid, B.M., C.M. Morton, V.J. Cardone and J.A. Greenwood, 1989. Development and Evaluation of a Wave Climate Database. Proceedings of the 2nd International Workshop on Wave Hind casting and Forecasting, Vancouver, B.C., April 25-28, 1989.
Canadian Climate Centre, 1991. Wind/Wave Hindcast Extremes for the East Coast of Canada. Report prepared by MacLaren Plansearch Limited and Oceanweather Inc. under DSS contract #KM169-7-6678.
MacLaren Plansearch Limited, 1989, Preparation of a Wind and Wave Climate Atlas, Phase I Interim Report - Initialization, Planning, Data Compilation, and Methodology, Report submitted To Transportation Development Centre, Transport Canada, Montreal, Quebec, March 89, TP 10867E.
Orchi, M.K. and E.N. Hubble, 1976. Six Parameter Wave Spectra. Proceedings of the 15th Coastal Engineering Conference. Honolulu, pp. 301-328.
Swail V.R., V.J. Cardone and B.M. Eid, 1989. Wind/Wave Hindcast Extremes for the East Coast of Canada. Proceedings of the 2nd International Workshop on Wave Hindcasting and Forecasting, Vancouver, B.C., April 25-28, 1989.