Overview of Tides and Water Levels

Transcription

1 Overview of Tides and Water Levels New Orleans, Baton Rouge, Lafayette, LA March 2009 Gerald Hovis, NOAA - National Ocean Service William Sweet, NOAA - National Ocean Service Chenglin Gan, NOAA - National Ocean Service

2 NOAA s National Ocean Service Center for Operational Oceanographic Products and Services Provide the National infrastructure, science, and technical expertise to monitor, assess, and distribute tide, current, water level, and other coastal oceanographic products and services necessary to support NOAA s mission.

3 CO-OPS Program Elements Physical Oceanographic Real-Time System (PORTS TM ) National Water Level Observation Network (NWLON) National Current Observation Program (NCOP)

4 NATIONAL OCEAN SERVICE WATER LEVEL AND CURRENT PROGRAMS SUPPORTING COASTAL MANAGERS NAVIGATION HABITAT Real-time tides/currents Hydrography Nautical Charting Monitor long-term sea level change Wetlands monitoring/restoration HAZARDS COASTAL COMMUNITIES Real-time tides/currents/meteorological for HAZMAT response Storm surge warnings Tsunami warnings data Tidal datums for shoreline delineation and marine boundaries Coastal environmental monitoring

5 Sea Level Monitoring Sea Levels Online Stephen Gill Dr. Chris Zervas

6 National Water Level Program National Water Level Observation Network Tom Landon Water Level Plus: Wind Speed/Direction Barometric Pressure Air/Water Temp. Conductivity/Temp Tsunami/Storm Surge Data Transmission

7 Tide Station Upgrades Storm Tide Monitoring NOAA Sentinels Tom are Landon designed to withstand wind and wave action from a Category 4 hurricane Elevated frame storm surge platforms: Lake Charles, LA Freshwater Bayou Locks, LA NOAA Sentinels Bay Waveland, MS, Shell Beach, LA, Amerada Pass, LA, Calcasieu Pass, LA. Shell Beach and Amerada Pass are the two sites planned for co-located CORS sites.

8 Storm QuickLook Storm Tide Monitoring Lori Fenstermacher The CO-OPS Storm QuickLook The product provides a synopsis of near real-time oceanographic and meteorological observations at locations affected by a tropical cyclone.

9 CO-OPS Website Overview Data Dissemination / Access User Services tide.predictions@noaa.gov

10 Tidal and Geodetic Datums Tidal and Geodetic Relationships Tidal Datums Team

11 Tidal Theory Tide Producing Forces Stephen Gill

12 Operation of Tide Gauges Tide Gauges and Benchmark Networks Operational Engineering Team

13 Observed Data to Tidal Datums Data to Datums Tidal Datums Team RAW SIX- MINUTE WATER LEVEL Verified Monthly Means Verified HI / LO ACCEPTED Datums Verified SIX-MINUTE WATER LEVEL Verified WATER LEVEL HOURLY ation_retrieve.shtml?type=datums

14 COASTAL Coastal Oceanographic Applications and Services of Tides And Lakes (COASTAL) Existing Elevations Allison Allen Variations in Relative Mean Sea Level Seattle, WA Elevation relative to local bench mark (meters) Linear trend: mm/yr Time 1950 (years)

15 Tidal Datum Computations Methods for Computing Tidal Datums Tidal Datums Team Primary Determination Average of 19-year data series defined by the National Tidal Datum Epoch to obtain Accepted Values Secondary or Tertiary Determination Comparison of means or tides to obtain an 19-year equivalent mean Modified Range Ratio Method Standard Method Direct Methods

16 Support of Hydro and Photo Observed Data, Zoning and TCARI Hydrographic Planning Team Discrete Tidal Zoning Tidal Constituent and Residual Interpolation (TCARI) TCARI Weighting TCARI Grid

17 IPET / CEPD / PDT Interagency Performance Evaluation Task Force Engineering and Design COMPREHENSIVE EVALUATION OF PROJECT DATUMS Guidance for Datum Evaluation IPET Vertical Datum Principal Findings Spatial and temporal variations of 0.2 to 3 ft were found between the geodetic datums and water level reference datums Vertical Control Project Delivery Team (PDT) Updating the reference elevation points for the region was not completed

18 VDatum Converting Tidal and Geodetic Datums Geoid Model Tidal Model Ellipsoid Model Ed Myers Bathy/Topo Digital Elevation Model USGS Topography NOAA Bathymetry VDatum ( Vertical Datum Transform Tool ) Resolve NOAA- USGS shoreline inconsistencies Consistently defined Shoreline from LIDAR data GIS users in the Coastal Community Charting and Other Applications Marine Boundaries and Legal Issues USGS Topo Sheet NOAA Shoreline MHW Shoreline Produced from LIDAR User-friendly utilization of DEM with new hi-res data in a GIS environment National Bathymetric Database

19 Overview of Tides and Water Levels New Orleans, Baton Rouge, Lafayette, LA March 2009 Gerald Hovis, NOAA - National Ocean Service William Sweet, NOAA - National Ocean Service Chenglin Gan, NOAA - National Ocean Service

20 NATIONAL TIDAL DATUM EPOCH (NTDE) A common time period to which tidal datums are referenced A specific 19 year period that includes the longest periodic tidal variations caused by the astronomic tide-producing forces. Averages out long term seasonal meteorological, hydrologic, and oceanographic fluctuations. Provides a nationally consistent tidal datum network (bench marks) by accounting for seasonal and apparent environmental trends in sea level that affects the accuracy of tidal datums. The NWLON provides the data required to maintain the epoch and make primary and secondary determinations of tidal datums.

21 SEATTLE, PUGET SOUND, WA VARIATIONS IN MEAN RANGE OF TIDE: Due to the 19-year cycle of Regression of the Moon s Nodes mean range (meters) 2.5 annual mean range monthly mean range

22 0.2 AVERAGE DIFFERENCES IN 19-YEAR MSL BETWEEN EPOCHS USING 32 LONG TERM STATIONS ELEVATION DIFFERENCE (meters) m m m TIME (years)

23 Anomalous Sea Level Trends

24 Use of 19 Year and 5 Year Tidal Epochs Deliver Meaningful Tidal Datums to User Communities

25 VERTICAL DATUM: A base elevation used to determine heights or depths. TIDAL DATUM Defined by a certain phase of the tide (ex. MHW) Are local datums In order that they may be recovered and updated when needed, such datums are referred to fixed points on land known as Bench Marks GEODETIC DATUM Is a set of reference points on the earth's surface against which position / elevation measurements are made.

26 MHHW

27 NATIONAL SPATIAL REFERENCE SYSTEM The National Spatial Reference System (NSRS): All geodetic control contained in the National Geodetic Survey (NGS) Data Base. A, B, First, Second and Third-Order horizontal and vertical control, Geoid models such as GEOID 03, precise GPS orbits and Continuously Operating Reference Stations (CORS), observed by NGS. Data submitted by other Federal, State, and local agencies, academic institutions and the private sector

28 GEODETIC DATUMS The National Geodetic Vertical Datum of 1929 (NGVD29): Vertical control datum established for vertical control in the United States by the general adjustment of Mean sea level held fixed at the sites of 26 tide gauges, 21 in the U.S.A. and 5 in Canada. The datum was defined by the observed heights of mean sea level at the 26 tide gauges The datum (was) not mean sea level, the geoid, or any other equipotential surface. The North American Vertical Datum of 1988 (NAVD 88): Vertical control datum established in 1991 by the minimum-constraint adjustment of the Canadian-Mexican-U.S. leveling observations. Held fixed the height of the primary tidal bench mark, referenced to the new International Great Lakes Datum of 1985 local mean sea level height value, at Father Point/Rimouski, Quebec, Canada. Additional tidal bench mark elevations were not used due to the demonstrated variations in sea surface topography,