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NetCDF Weather Data from Unidata By David Maidment, Tim Whiteaker and Cedric David Center for Research in Water Resources University of Texas at Austin
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NetCDF Weather Data from Unidata Using real-time weather data in ArcGIS Sphere to Spheroid transformations OpenMI system for model interfacing
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NetCDF Weather Data from Unidata Using real-time weather data in ArcGIS Sphere to Spheroid transformations OpenMI system for model interfacing
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Ocean Sciences Unidata Universities Corporation for Atmospheric Research is a large NSF-supported atmospheric science organization in Boulder, CO UCAR was formed in 1957 Unidata provides real-time atmospheric science data to academic institutions Unidata opened in 1983 Weather data and forecasts for the last 7 days on Motherlode Earth Sciences Atmospheric Sciences National Science Foundation Geosciences Directorate UCAR CUAHSI Unidata HIS
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Unidata NetCDF Files Catalog of Datasets –http://motherlode.ucar.edu:8080/thredds/catalog.htmlhttp://motherlode.ucar.edu:8080/thredds/catalog.html
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NCEP NAM 12km Data North American Model Continuous grid over the continental US Model runs are made at 06Z, 12Z, 18Z and 00Z Forecasts every 3 hours out to 84 hours Accessed With –OPENDAP –HTTPServer –WCS –NetcdfServer
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Netcdf Server Query for subset of data with Web Form Download netCDF file
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Query Via URL Format documented at –http://motherlode.ucar.edu:8080/thredds/docs/Netcdf Server.htmlhttp://motherlode.ucar.edu:8080/thredds/docs/Netcdf Server.html Example: –http://motherlode.ucar.edu:8080/thredds/ncServer/mo del/NCEP/NAM/CONUS_12km/NAM_CONUS_12km _20060803_1800.grib2? grid=Total_precipitation &north=35&south=30&west=-90&east=-85 &time_start=0.0&time_end=12.0 Data Type Bounding Box Start/End Time
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NDFD Data Also Available NWS National Digital Forecast Database Gridded forecasts of sensible weather elements 5km resolution over continental US http://motherlode.ucar.edu:8080/thredds/c atalog/model/NCEP/NDFD/CONUS_5km/c atalog.htmlhttp://motherlode.ucar.edu:8080/thredds/c atalog/model/NCEP/NDFD/CONUS_5km/c atalog.html
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Viewing NetCDF in ArcMap
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Unidata Weather in ArcMap Total Precipitation 7/21/06 – 7/24/06 Demo
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NetCDF Weather Data from Unidata Using real-time weather data in ArcGIS Sphere to Spheroid transformations OpenMI system for model interfacing
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Sphere – Spheroid Transformation We think of the earth as a sphere It is actually a spheroid, slightly larger in radius at the equator than at the poles Weather models are computed on a spherical earth Hydrologic models and data Are on a spheroidal earth
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Latitude and Longitude on a Sphere Meridian of longitude Parallel of latitude X Y Z N E W =0-90°S P O R =0-180°E =0-90°N Greenwich meridian =0° Equator =0° =0-180°W - Geographic longitude - Geographic latitude R - Mean earth radius O - Geocenter
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Definition of Latitude, (1) Take a point S on the surface of the ellipsoid and define there the tangent plane, mn (2) Define the line pq through S and normal to the tangent plane (3) Angle pqr which this line makes with the equatorial plane is the latitude , of point S O S m n q p r
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Geographic and Geodetic Latitudes N E W = 0 =0-90°S P O R =0-90°N On a spherical earth, the normal line always passes through the geocenter (O) of the earth – “geographic latitude” g O S n q p r On a spheroidal earth, the normal Line pq does not pass through the geocenter (O) of the earth – “geodetic latitude”,
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Application: hydrologic modeling using weather model data ArcGIS 9.2 is netCDF CF-1 compliant ? + = Watersheds on spheroid Weather data on sphere
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Sphere – spheroid transformations http://www.crwr.utexas.edu/gis/gishydro06/index.htm
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NetCDF Weather Data from Unidata Using real-time weather data in ArcGIS Sphere to Spheroid transformations OpenMI system for model interfacing
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Project sponsored by the European Commission to promote integration of water models Software standards for model linking Uses model core as an “engine” http://www.openMI.org
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OpenMI – Links Data and Simulation Models CUAHSI Observations Data Model as an OpenMI component Simple River Model Trigger (identifies what value should be calculated)
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Typical model architecture Application User interface + engine Engine Simulates a process – flow in a channel Accepts input Provides output Model An engine set up to represent a particular location e.g. a reach of the Thames Engine Output data Input data Model application Run Write Read User interface
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AcceptsProvides Rainfall (mm) Runoff (m 3 /s) Temperature (Deg C) Evaporation (mm) AcceptsProvides Upstream Inflow (m 3 /s) Outflow (m 3 /s) Lateral inflow (m 3 /s) Abstractions (m 3 /s) Discharges (m 3 /s) River Model Linking modelled quantities
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Data transfer at run time Rainfall runoff Output data Input data User interface River Output data Input data User interface GetValues(..)
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Models for the processes River (InfoWorks RS) Rainfall (database) Sewer (Mouse) RR (Sobek-Rainfall -Runoff)
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Data exchange 3 Rainfall.GetValues River (InfoWorks-RS) Rainfall (database) Sewer (Mouse) 2 RR.GetValues 7 RR.GetValues RR (Sobek-Rainfall -Runoff) 1 Trigger.GetValues 6 Sewer.GetValues call data 4 5 8 9
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Conclusions Use of NetCDF in ArcGIS permits direct access to real-time weather information from Unidata A sphere to spheroid transformation is required to bring the weather data into a regular map coordinate system OpenMI promises to be a good way to interconnect hydrologic data and models
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