United States Average Annual Precipitation, 1961-1990

Frequently-anticipated questions:

• What does this data set describe?
  1. How should this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  3. What similar or related data should the user be aware of?
• How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

1. How should this data set be cited?

   Chris Daly, Spatial Climate Analysis Service, and George Taylor, the Oregon Climate Service at Orego, 200009, United States Average Annual Precipitation, 1961-1990: Spatial Climate Analysis Service, Oregon State University; USDA - NRCS National Water and Climate Center, Portland, Oregon; USDA - NRCS National Cartography and Geospatial Center, Fort Worth, Texas, Corvallis, OR, USA.

   Online Links:

   • <http://nationalatlas.gov/atlasftp.html?openChapters=chpclim#chpclim>
   • <http://www.ncgc.nrcs.usda.gov/products/datasets/climate/data/index.html>

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -124.762142

   East_Bounding_Coordinate: -66.957227

   North_Bounding_Coordinate: 49.371731

   South_Bounding_Coordinate: 24.545220

3. What does it look like?

4. Does the data set describe conditions during a particular time period?

   Beginning_Date: 19610101

   Ending_Date: 31-Dec-1990

   Currentness_Reference: Ground condition

5. What is the general form of this data set?

   Geospatial_Data_Presentation_Form: Map

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?

      This is a Vector data set. It contains the following vector data types (SDTS terminology):

      • GT-polygon composed of chains (6243)

   2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.02083333. Longitudes are given to the nearest 0.02083333. Latitude and longitude values are specified in Decimal degrees.

      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is GRS1980.
      The semi-major axis of the ellipsoid used is 6378137.0.
      The flattening of the ellipsoid used is 1/298.257222.
      

7. How does the data set describe geographic features?

   Area of equal average annual precipitation (described by prismp020.dbf)

   Each polygon represents an area with a constant value for the average annual precipitation, as determined by the PRISM model. (Source: Spatial Climate Analysis Service PRISM Project)

   Shape

   The representation of the entity in the data. (Source: U.S. Geological Survey)

   Value	Definition
   Polygon	A 2-dimensional element.

   Area

   The size of the shape in square coverage units. In the distributed file, coverage units represent square decimal degrees. (Source: Natural Resources Conservation Service)

   Range of values
   Minimum:	0.00000
   Maximum:	115.09402

   Perimeter

   The perimeter of the shape in coverage units. In the distributed file, coverage units represent decimal degrees. (Source: Natural Resources Conservation Service)

   Range of values
   Minimum:	0.00647
   Maximum:	874.33448

   Prism0p020

   Internal feature number. (Source: Natural Resources Conservation Service)

   Range of values
   Minimum:	2
   Maximum:	6244

   Range

   The average annual precipitation. (Source: Spatial Climate Analysis Service)

   Range of values
   Minimum:	0.000
   Maximum:	200.000
   Units:	Inches
   Resolution:	2.5

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • Chris Daly, Spatial Climate Analysis Service
   • George Taylor, the Oregon Climate Service at Oregon State University

2. Who also contributed to the data set?

3. To whom should users address questions about the data?
   Spatial Climate Analysis Service
   316 Strand Agricultural Hall, Oregon State University
   Corvallis, OR 97331-2202
   

   541-737-2531 (voice)
   541-737-5710 (FAX)
   [email protected]
   

Why was the data set created?

These data are intended for geographic display and analysis at the national level, and for large regional areas. The data should be displayed and analyzed at scales appropriate for 1:2,000,000-scale data. No responsibility is assumed by the Spatial Climate Analysis Service, the USDA - NRCS National Water and Climate Center, the USDA - NRCS National Cartography and Geospatial Center, or the U.S. Geological Survey in the use of these data.

How was the data set created?

1. From what previous works were the data drawn?

   PRISM (source 1 of 7)

   Spatial Climate Analysis Servic, Oregon State University, 1998, Parameter-elevation Regressions on Independent Slopes Model (PRISM): Spatial Climate Analysis Service, Corvallis, OR, USA.

   Type_of_Source_Media: Proprietary software

   Source_Contribution:

   PRISM was used to create gridded estimates of precipitation from point observations and digital elevation model data. For a more detailed description of the PRISM process, see: Daly, C., W.P. Gibson, G.H. Taylor, G.L. Johnson, P. Pasteris. 2002. A knowledge-based approach to the statistical mapping of climate. Climate Research, 22: 99-113, <http://www.ocs.orst.edu/pub/prism/docs/climres02-kb_approach>_ statistical_mapping-daly.pdf>.

   FILTER (source 2 of 7)

   Spatial Climate Analysis Servic, Oregon State University, 1998, Gaussian Filter: Spatial Climate Analysis Service, Corvallis, OR, USA.

   Type_of_Source_Media: Proprietary software

   Source_Contribution:

   The Gaussian filter was used to change the resolution of raster data from 4 km to 2 km. The Gaussian filter was implemented as custom software written in FORTRAN. For information about Gaussian filters see: Barnes, Stanley L., 1964; A Technique for Maximizing Details in Numerical Weather Map Analysis. Journal of Applied Meteorology, 3, 396- 409.

   CLIM81 (source 3 of 7)

   National Climatic Data Center (NCDC), 1991, U.S. National 1961-1990 Climate Normals, Climatography of the United States No. 81 - Monthly Normals: National Climatic Data Center, Asheville, NC, USA.

   Other_Citation_Details:

   For more information on this source, please see <http://www.ncdc.noaa.gov/oa/climate/normals/usnormalshist.html#clim81>.

   Type_of_Source_Media: Online database

   Source_Contribution: Location and values of known average annual precipitation.

   SNOTEL (source 4 of 7)

   Natural Resources Conservation Service (NRCS), 1991, Cooperative Snow Survey Data of Federal-State-Private Cooperative Snow Surveys (SNOTEL): Cooperative Snow Survey Data of Federal-State-Private Cooperative Snow Surveys Annual issue for Western US states, Natural Resources Conservation Service, Portland, OR, USA.

   Other_Citation_Details:

   For more information on this source, please see <http://www.wcc.nrcs.usda.gov/snow/>.

   Type_of_Source_Media: Database, paper, and online

   Source_Contribution:

   Location and values of known average monthly and annual precipitation.

   LOCAL (source 5 of 7)

   Natural Resources Conservation , National Water and Climate Center, Unpublished material, Local precipitation monitoring networks.

   Type_of_Source_Media: Digital files

   Source_Contribution: Location and values of known average annual precipitation.

   DEM (source 6 of 7)

   Agency, Defense Mapping , 1985, 1:250,000-scale Digital Elevation Models (DEM): U.S. Geological Survey, Washington, DC.

   Online Links:

   • <http://edc.usgs.gov/geodata/>

   Type_of_Source_Media: Digital files

   Source_Contribution:

   Terrain surface input to the PRISM model for estimation of precipitation between known points.

   Atlas-ST (source 7 of 7)

   U.S. Geological Survey, 1999, State Boundaries of the United States: U.S. Geological Survey, Reston, VA.

   Online Links:

   • <http://nationalatlas.gov/atlasftp.html?openChapters=chpbound#chpbound>

   Type_of_Source_Media: Online

   Source_Contribution:

   This file was used to determine the boundary of the data included.

2. How were the data generated, processed, and modified?

   Date: Apr-1998 (process 1 of 7)

   The DEM resolution was changed to 4 km using the Gaussian filter.

   Data sources used in this process:

   • DEM
   • FILTER

   Date: Apr-1998 (process 2 of 7)

   All the station data was combined into one master data set.

   Data sources used in this process:

   • CLIM81
   • SNOTEL
   • LOCAL

   Date: Apr-1998 (process 3 of 7)

   Data from CLIM81, SNOTEL, and LOCAL were incorporated into the PRISM model and combined with the DEM to produce the initial 4 km-resolution PRISM model output.

   Data sources used in this process:

   • PRISM
   • DEM
   • CLIM81
   • SNOTEL
   • LOCAL

   Date: Apr-1998 (process 4 of 7)

   The PRISM model output was converted from 4 km to 2 km using a Gaussian filter.

   Data sources used in this process:

   • FILTER

   Date: Apr-1998 (process 5 of 7)

   The 2 km raster data was contoured using Arc/INFO.

   Date: Apr-1998 (process 6 of 7)

   Adjacent isohyets were converted to areas or polygons using a custom- designed macro (AML) in Arc/INFO.

   Date: Feb-2000 (process 7 of 7)

   The coverage was created by the Spatial Climate Analysis Service using custom software. The Natural Resources Conservation Service, National Cartography and Geospatial Center edited the file in Arc/INFO to match the coastlines and boundaries (Atlas-ST) from the National Atlas of the United States. The data were converted to shapefile format for inclusion in the National Atlas of the United States.

   Data sources used in this process:

   • Atlas-ST

3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

1. How well have the observations been checked?

   Point estimates of precipitation from the U.S. National 1961-1990 Climate Normals were subjected to manual quality control checks by the National Climatic Data Center (NCDC). PRISM precipitation estimates were reviewed by the PRISM Evaluation Group, a panel of climatologists, meteorologists, and hydrologists. The task of this group was to assess the assumptions made by the model and compare model output with the best available precipitation maps from several western States. The group found that the PRISM maps equaled or exceeded the accuracy of the best maps available.

2. How accurate are the geographic locations?

3. How accurate are the heights or depths?

4. Where are the gaps in the data? What is missing?

   This data set includes observations and interpolated values for the 48 contiguous United States and the District of Columbia, for the climatological period 1961-1990. This data set is a compilation of the best available data from the various data sources.

5. How consistent are the relationships among the observations, including topology?

   Precipitation data were derived from two main sources, NCDC Climate Normals and NRCS Cooperative Snow Survey Data (SNOTEL). In general, NCDC stations are located at low elevations and in valley bottoms, and encompass the entire United States. SNOTEL stations are located primarily at high elevations in the western United States.

   Polygon and chain-node topology are present. Checks were made to ensure that no two adjacent polygons are labeled with the same precipitation value. A manual spot check was made of peaks, depressions, and islands.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: None.

Use_Constraints:

None. Acknowledgement of the PRISM model, the Spatial Climate Analysis Service at Oregon State University, the Natural Resources Conservation Service (NRCS) Water and Climate Center, the NRCS National Cartography and Geospatial Center (NCGC), and (or) the National Atlas of the United States would be appreciated in products derived from these data.

1. Who distributes the data set? (Distributor 1 of 2)
   USDA - NRCS National Cartography and Geospatial Center
   501 W Felix, PO Box 6567
   Ft. Worth, TX 76115
   USA
   

   817-509-3366 (voice)
   [email protected]
   

2. What's the catalog number I need to order this data set?

3. What legal disclaimers am I supposed to read?

   These spatial datasets, associated metadata and documentation are provided at media cost, without restriction or restraint of use, from the USDA- Natural Resources Conservation Service and the Spatial Climate Analysis Service. The project was directed and sponsored by the NRCS National Water and Climate Center in Portland, Oregon. None of the agencies involved, nor any of their employees, make any warranty, expressed or implied, or assume any legal liability or responsibility for the accuracy, completeness, or misuse of the data, nor represent that its use would not infringe privately owned rights. The agencies involved are not responsible for damage, transmission of viruses, or computer contamination through the distribution of this data set. Neither do they assume any responsibility for the usefulness of any information, apparatus, product, or process disclosed in this metadata. Reference in this metadata to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government, the State of Oregon, or any agency thereof. Any views and opinions of authors expressed in this metadata do not necessarily state or reflect those of the United States Government, the State of Oregon, or any agency thereof.

4. How can I download or order the data?
   • Availability in digital form:

     Data format:	ESRI Shapefile
     Network links:	<http://www.ncgc.nrcs.usda.gov/products/datasets/climate/data/index.html>

   • Cost to order the data: None

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1. Who distributes the data set? (Distributor 2 of 2)
   Earth Science Information Center, U.S. Geological Survey
   507 National Center
   Reston, VA 20192
   

   1-888-ASK-USGS (1-888-275-8747) (voice)
   

   Contact_Instructions:

   In addition to the address above there are other ESIC offices throughout the country. A full list of these offices is at <http://ask.usgs.gov/esic_index.html>.

2. What's the catalog number I need to order this data set?

3. What legal disclaimers am I supposed to read?

   Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made by the U.S. Geological Survey regarding the utility of the data on any other system, nor shall the act of distribution constitute any such warranty. No responsibility is assumed by the U.S. Geological Survey in the use of these data.

4. How can I download or order the data?
   • Availability in digital form:

     Data format:	ESRI Shapefile
     Network links:	<http://nationalatlas.gov/atlasftp.html?openChapters=chpclim#chpclim>

     Data format:	SDTS
     Network links:	<http://nationalatlas.gov/atlasftp.html?openChapters=chpclim#chpclim>

   • Cost to order the data: There is no charge for the map layer.

Who wrote the metadata?

Dates:

Last modified: 07-Jun-2006

Metadata author:

Peg Rawson
U.S. Geological Survey
12201 Sunrise Valley Drive
Reston, VA 20192
USA

703-648-4183 (voice)
[email protected]

Metadata standard:

FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)