Metadata for Precipitation Yearly Normal for 1981-2010 from PRISM Metadata for Precipitation Yearly Normal for 1981-2010 from PRISM

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Identification Information:

Citation:

Originator: Montana Climate Office
Publication date: 02/11/2015
Title: Precipitation Yearly Normal for 1981-2010 from PRISM
Online linkage: ftp://mco.cfc.umt.edu/prcp/PRISM/yearly_normals/Readme.html

Browse graphic file name: http://mco.cfc.umt.edu/images/MCOPrecipNormalThumbnail.jpg
Browse graphic file description: Montana Climate Office PRISM precipitation yearly normal graphic
Browse graphic file type: JPEG

Abstract:

This raster dataset shows the yearly normal precipitation (rain plus melted snow) in millimeters with a grid cell resolution of 5151-meters (~5-kilometers). The normal is defined as the arithmetic mean of the annual sum of daily precipitation over a 30-year period. The current 30-year interval for calculating normals is 1980 to 2010. The standard deviation is also provided for calculating daily or annual z-score departures or similar statistics. Normals serve as a reference point for comparing current climatological trends to that of the past. A 30-year period is long enough to filter out any inter-annual variation or anomalies, but sufficiently short enough to reflect longer term climatic trends. The 30-year interval was selected by international agreement, based on the recommendations of the International Meteorological Conference in Warsaw in 1933.

Purpose:

Gridded topographic-climatic datasets are increasingly used to drive many ecological and hydrological models and assess climate change impacts. These datasets can be an invaluable tool for spatially explicit ecological and hydrological modelling, for facilitating better end-user understanding, and for advancing community-driven model improvements. The PRISM (Parameter-elevation Regressions on Independent Slopes Model) spatially gridded precipitation dataset provides modeled estimates of daily total precipitation (rain plus melted snow) for the conterminous United States. PRISM data products are produced by the PRISM Climate Group of the the Northwest Alliance for Computational Science and Engineering at Oregon State University (http://prism.oregonstate.edu). PRISM products are distributed in a licensed 800-meter grid format and a public 4-kilometer format in a North American 1983 (NAD83) projection. The Montana Climate Office redistributes this product in Montana State Plane NAD83 projection with a 5151-meter grid in both geotiff and Esri geodatabase format. The PRISM interpolation method was used to develop data sets that reflected, as closely as possible, the current state of knowledge of spatial climate patterns in the United States. PRISM calculates a climate–elevation regression for each digital elevation model (DEM) grid cell, and stations entering the regression are assigned weights based primarily on the physiographic similarity of the station to the grid cell. Factors considered are location, elevation, coastal proximity, topographic facet orientation, vertical atmospheric layer, topographic position, and orographic effectiveness of the terrain. Station data were spatially quality controlled. This grid was initially modelled with PRISM at 30-arc-second (~800-m) resolution to produce the source . This source grid was then upscaled to 2.5-arc-minute (~4-km). During the process of re-projecting the grid from NAD83 to Montana State Plane the nominal grid size for the re-sampling is ~5 km.

Supplemental information:

Processed from .bil raster file source using Python 2.7 code maintained by the Montana Climate Office.

Time period of content:

Beginning date: 01/01/1981
Beginning time: 000000
Ending date: 12/31/2010
Currentness reference:: The bounding rectangle for all 4th-code NRCS hydrologic units that intersect with the boundary of the State of Montana.

Status:

Progress: Complete
Maintenance and update frequency: As needed

Access constraints: None

Use constraints:

The Montana Climate Office (MCO) provides this product/service for informational purposes only. The MCO did not produce it for, nor is it suitable for legal, engineering, or surveying purposes. Consumers of this information should review or consult the primary data and information sources to ascertain the viability of the information for their purposes. The MCO provides these data in good faith but does not represent or warrant its accuracy, adequacy, or completeness. In no event shall the MCO be liable for any incorrect results or analysis; any direct, indirect, special, or consequential damages to any party; or any lost profits arising out of or in connection with the use or the inability to use the data or the services provided. The MCO makes these data and services available as a convenience to the public, and for no other purpose. The MCO reserves the right to change or revise published data and/or services at any time.

Point of contact:

State Climatologist
Director of Montana Climate Office
Montana Climate Office
32 Campus Drive
Missoula, Montana 59812-0576
Telephone: 406.243.6793
E-Mail: state.climatologist@umontana.edu

Point of contact:

Michael D. Sweet
Research and Information Systems Specialist
Montana Climate Office
32 Campus Drive
Missoula, Montana 59812-0576
Telephone: 406.243.5265
E-Mail: michael.sweet@umontana.edu

Data set credit:

PRISM Climate Group, Oregon State University, http://prism.oregonstate.edu and the Montana Climate Office (http://climate.umt.edu/)

Data Quality Information:

Logical consistency report:

Value range resulting from bilinear transformation to Montana State Plane projection is within expected range. NoData values are assigned where they existed in the source representation.

Completeness report:

Number of NoData items with respect to the total number of NoData that should have been present

Lineage:

Process step:: Source at ftp://prism.nacse.org/daily/ppt/is programmatically downloaded and projected from NAD83 geographic cooridinates to Montana State Plane NAD83 using the Esri ArcGIS ProjectRaster_management method. The method uses a bilinear transformation, with a raster cell size of 5151.31156123134 meters, and registers the grid cell boundary at Montana State Plane coordinates [538267.150, 308212.258]. PRISM data projected to Montana State Plane NAD83 is extracted to an area-of-interest (ftp://mco.cfc.umt.edu/resources/MCO/Area-of-Interest/BoundariesMSP.gdb/area-of-interest) defined by the Montana Climate Office to encompass all major sub-basins that intersect with Montana's border. The Esri ArcGIS Spatial Analyst ExtractByMask_sa method is used. For the extract method, the source is used as a snap raster to maintain alignment of the grid cells. Pyramids are built for the result using Esri ArcGIS BuildPyramids_management method.
Process step:: Daily precipitation data is summed by year, the metadata updated, and published as yearly totals.
Process step:: An average is calculated for all years across the time period.