Identification_Information: Citation: Citation_Information: Originator: Chris Daly of PRISM Services, George Taylor of the Oregon Climate Service Publication_Date: 199707 Title: Wyoming Average Annual Precipitation, 1961-1990 Publication_Information: Publication_Place: Corvallis, Oregon, USA Publisher: Oregon Climate Service, Oregon State University Online_Linkage: Online_Linkage: Description: Abstract: Spatially gridded precipitation, 4 km2 cell size. Weather stations were used as points to interpolate the precipitation contours based on averages of annual precipitation from 1961-1990. Interpolation was done using the PRISM model, developed by Chris Daly of PRISM Services/Oregon State University. Care should be taken in estimating precipitation values at any single point on the map. Precipitation estimated for each grid cell is an average over the entire area of that cell; thus, point precipitation can be estimated at a spatial precision no better than half the resolution of a cell. For example, the Oregon precipitation data was distributed at a resolution of approximately 4km. Therefore, point precipitation can be estimated at a spatial precision no better than 2km. However, the overall distribution of precipitation features is thought to be accurate. Purpose: Display the spatial distribution of annual average precipitation Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 1961 Ending_Date: 1990 Currentness_Reference: publication date Status: Progress: complete Maintenance_and_Update_Frequency: as needed Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -111 East_Bounding_Coordinate: -103.8 North_Bounding_Coordinate: 45 South_Bounding_Coordinate: 41 Keywords: Theme: Theme_Keyword: precipitation Theme_Keyword: contours Theme_Keyword: kriging Theme_Keyword_Thesaurus: None Place: Place_Keyword: Wyoming Place_Keyword_Thesaurus: None Access_Constraints: none Use_Constraints: Acknowledgement of PRISM Services and the Oregon Climate Service required in products derived from these data. See dataset_credit for more contact information. Point_of_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Data Manager Contact_Organization: Spatial Data and Visualization Center Contact_Address: Address_Type: mailing address Address: Box 3355 University Station City: Laramie State_or_Province: Wyoming Country: USA Postal_Code: 82071 Contact_Voice_Telephone: 307-766-2735 Contact_Electronic_Mail_Address: n/a Hours_of_Service: 8 AM to 5 PM MST Native_Data_Set_Environment: The data was created in and is stored in Arc/Info 7.0.4 software for Unix operating system. The dataset is in raster format (GRID) Data_set_Credit: George Taylor, State Climatologist, Oregon Climate Service Strand Ag Hall 326, Oregon State U., Corvallis, OR 97331-2209 (541)737-5705 taylor@oce.orst.edu Chris Daly, Oregon State University, Forestry sciences Lab 3200 SW Jefferson Way, Oregon State U., Corvallis OR 97331-2209 (541)750-7436 daly@fsl.orst.edu Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: Attributing is dependent on the PRISM model, please see Process Steps for more information about the model and its limitations. Quantitative_Attribute_Accuracy_Assessment: Attribute_Accuracy_Value: n/a Attribute_Accuracy_Explanation: n/a Completeness_Report: Point estimates of precipitation originated from the following sources: 1)National Weather Service Cooperative (COOP) stations, 2) Natural Resource Conservation Service (NRCS) SNOTEL, 3) local networks. As better data or additional stations become available, PRISM model runs may be made to improve this data set. All COOP stations were run through quality control checks by the National Climatic Data Center(NCDC). SNOTEL data was quality control checked by the NRCS and Oregon Climate Service. The validity of data from local networks was compared with COOP and SNOTEL data. Logical_Consistency_Report: does not apply to raster data Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: Accuracy of this data set is based on the original specification of the Defense Mapping Agency 1 degree digital elevation models (DEM). The stated accuracy of the original DEMs are 130m circular error with 90% probability. Lineage: Source_Information: Source_Citation: Citation_Information: Originator: Oregon Climate Service Publication_Date: 1997 Title: Parameter-elevation regressions on independent slopes model (PRISM) Type_of_Source_Media: computer program Source_Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 1997 Source_Currentness_Reference: date of publication Source_Citation_Abbreviation: PRISM Source_Contribution: used to interpolate precipitation from point data Process_Step: Process_Description: There are many methods of interpolating precipitation from monitoring stations to grid points. Some provide estimates of acceptable accuracy in flat terrain, but few have been able to adequately explain the extreme, complex variations in precipitation that occur in mountainous regions. Significant progress in this area has been achieved through the development of PRISM (Parameter-elevation Regressions on Independent Slopes Model). PRISM is an analytical model that uses point data and a digital elevation model (DEM) to generate gridded estimates of monthly and annual precipitation (as well as other climatic parameters). PRISM is well suited to regions with mountainous terrain, because it incorporates a conceptual framework that addresses the spatial scale and pattern of orographic precipitation. The primary effect of orography on a given mountain slope face is to cause precipitation to vary strongly with elevation. Orographic effects operate at a hierarchy of spatial scales. For example, a large mountain barrier can enhance precipitation over a broad area windward of the crest through forced uplift of moist air flow. Imbedded within this major effect are minor, smaller-scale precipitation perturbations caused by, say, vertical air motion associated with river valleys carved into the barrier. Orographic effects caused by the large- scale (>10 km) terrain features typically explain most of the spatial variation in climatological precipitation in mountainous terrain. In addition, the density of most routine precipitation networks is sufficient to resolve only the larger-scale orographic effects at best. Therefore, it is not surprising that relationships between observed precipitation and elevation are generally strengthened when the elevation of each data point is given in terms of its height on a smoothed terrain (e.g., at 10-km resolution), which we might term its effective "orographic" elevation. The relationship between precipitation and orographic elevation varies from one slope face to another, depending on location and orientation. Thus, a mountainous landscape can be thought of as a mosaic of smoothed topographic faces, or "facets," each experiencing a different orographic regime. Each topographic facet is a contiguous area over which the slope orientation is reasonably constant. Topographic facets are best delineated by using a DEM at a resolution that closely matches the smallest orographic scale supported by the data, thereby reducing the number of facets delineated at terrain scales too small to be resolved by the data. In operation, PRISM 1) estimates the "orographic" elevation of each precipitation station using a smoothed DEM; and 2) assigns each DEM grid cell to a topographic facet by assessing slope orientation. PRISM then estimates precipitation at each DEM cell by 3) using a windowing technique to develop a weighted precipitation/DEM-elevation regression function from nearby rainfall stations, favoring those on the cell's topographic facet; and 4) predicting precipitation at the cell's DEM elevation with this regression function. Whenever possible, PRISM calculates a prediction interval for the estimate, which is an approximation of the uncertainty involved. By using many precipitation/DEM-elevation relationships developed within local windows and on individual topographic facets, rather than a single domain-wide relationship, PRISM continually adjusts its frame of reference to accommodate local and regional changes in orographic regime. Development of state analysis by Oregon Climate Service began with collection of precipitation data from locations within the state and nearby stations within contiguous states/provinces. Two primary data sets were used: National Climatic Data Center (NCDC) cooperative stations and Natural Resources Conservation Service (NRCS) SNOTEL stations. The period 1961-90 was used for the analysis. Mean monthly values for stations which had at least 27 years of data were used without modification. Data sets for those with at least 15 but less than 27 years of data were modified by applying a least-squares fit to data from a representative nearby station, yielding a 30-year average. PRISM was run for each month, and the months summed to obtain an annual map. Output consisted of precipitation values for each grid cell on a 2.5-minute latitude/longitude DEM. The gridded output was then imported into GRASS for plotting and evaluation. Hard copies of the annual map were circulated to experts familiar with the state's climate, and comments, suggestions, and additional data points were solicited. The annual map was revised repeatedly to reflect this expert input. This analysis is thought to be of quality and accuracy comparable to that of manual isohyetal methods. In addition, the PRISM analysis incorporates the latest station data with easy updating capabilities, and uses a reasonably objective method that is reproducible and GIS-compatible. Also refer to : Daly, C., R.P. Neilson, and D.L. Phillips, 1994: A Statistical-Topographic Model for Mapping Climatological Precipitation over Mountainous Terrain. J. Appl. Meteor., 33,140-158. Process_Date: 199707 Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: Raster Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Map_Projection: Map_Projection_Name: Lambert Conformal Conic Lambert_Conformal_Conic: Standard_Parallel: 33 Standard_Parallel: 33 Longitude_of_Central_Meridian: -107.5 Latitude_of_Projection_Origin: 41 False_Easting: 0.00000 False_Northing: 0.00000 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: coordinate pair Coordinate_Representation: Abscissa_Resolution: 1.0 Ordinate_Resolution: 1.0 Planar_Distance_Units: METERS Geodetic_Model: Horizontal_Datum_Name: North American Datum of 1983 Ellipsoid_Name: GRS1980 Semi-major_Axis: 6378137 Denominator_of_Flattening_Ratio: 298.257 Entity_and_Attribute_Information: Overview_Description: Entity_and_Attribute_Overview: Each grid cell contains estimated precipitation in millimeters (VALUE attribute) and in inches (INCHES attribute) Entity_and_Attribute_Detail_Citation: Not Available Distribution_Information: Distributor: Contact_Information: Contact_Person_Primary: Contact_Person: Data Manager Contact_Organization: Spatial Data and Visualization Center Contact_Address: Address_Type: mailing address Address: Box 3355 University Station City: Laramie State_or_Province: Wyoming Country: USA Postal_Code: 82071 Contact_Voice_Telephone: 307-766-2735 Contact_Electronic_Mail_Address: n/a Distribution_Liability: The distributor shall not be held liable for improper or incorrect use of this data, based on the description of appropriate/inappropriate used described in this metadata document. The distributor makes no claims for the data's suitability for other purposes. Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Format_Name: ARCE (Arc/Info export) Format_Version_Number: 7.0.4 Format_Version_Date: 1995 File_Decompression_Technique: Export file was created using defaults, no compression Digital_Transfer_Option: Online_Option: Computer_Contact_Information: Network_Address: Network_Resource_Name: ftp.sdvc.uwyo.edu or http://www.sdvc.uwyo.edu/clearinghouse Access_Instructions: The data can be accessed online two different way: by anonymous ftp or by the world wide web. The anonymous ftp server is ftp.sdvc.uwyo.edu, and the data is stored in the /pub/gis directory. The WWW page is http://www.sdvc.uwyo.edu/clearinghouse. Instructions are provided on-line for downloading and importing the data. Online_Computer_and_Operating_System: Both the ftp and WWW server which this data is available from is a Silicon Graphics Challenge server, running the IRIX 6.2 UNIX operating system. Fees: No fees are required for downloading the data that is on-line. Some fees may be required to cover costs of tapes if data is required on tape media. Metadata_Reference_Information: Metadata_Date: 199806 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Margo Herdendorf Contact_Address: Address_Type: mailing address Address: Box 3355 University Station City: Laramie State_or_Province: Wyoming Postal_Code: 82071 Country: USA Contact_Voice_Telephone: 307-766-2735 Contact_Electronic_Mail_Address: meh@uwyo.edu Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata Metadata_Standard_Version: 19940608