Introduction to the PRISM Weather and Climate Mapping System Christopher Daly, Ph.D. Founder and Director, PRISM Climate Group Author, PRISM Climate Mapping System Northwest Alliance for Computational Science and Engineering Oregon State University

PRISM Climate Group Overview Applied research team since 1991, founded and directed by Dr. Christopher Daly Housed within the Northwest Alliance for Computational Science and Engineering, College of Engineering, Oregon State University Climate mapping center for the USDA; de facto climate mapping center for the US Federal sponsors cut across many departments and disciplines, including agencies within DOE, DOD, DOC, DOI, USDA, NSF, EPA

What is PRISM? There are many locations in the US for which no weather observations exist. To create a continuous weather or climate map across the country, station observations are fed into a sophisticated computer model called PRISM (Parameter-elevation Regressions on Independent Slopes Model). PRISM estimates weather and climate variables, such as temperature and precipitation, on a grid of millions of pixels, each measuring about 0.5 mile across the entire conterminous US, every day. Weather maps show what occurs from day to day. Climate maps show long-term averages of weather over a period of 10-30 years PRISM is used to produce both kinds of maps.

How Does PRISM Work? For grid cells where no observations exist, PRISM mimics the thinking an expert meteorologist would follow. The model simulates how weather and climate varies with elevation, and accounts for coastal effects, temperature inversions, and terrain barriers that can cause rain shadows. Grand Canyon temperature map: PRISM incorporates the effects of elevation PRISM Station Grid Cell

High Quality Station Data Each day, the PRISM Climate Group collects data from over 20,000 precipitation and 6,000 temperature stations. These include all of NOAA’s major networks; those operated by the US Forest Service, Bureau of Reclamation, and USDA; the large CoCoRaHS precipitation network; state and regional systems operating in California, Colorado, Florida, Minnesota, North Dakota, and Oklahoma; and Environment Canada stations. More networks are being added all the time. The quality of the station observations is a key factor in the accuracy of the datasets. PRISM’s comprehensive quality control system ensures that only the most accurate observations are used. PRISM personnel have close relationships with many data providers, and alert them to issues as they arise. Automated Colorado Ag Weather Network Station Manned CoCoRaHS rainfall station Photos: Colorado State University

Reporting Precipitation on 1 July 2014 PRISM Stations Reporting Precipitation on 1 July 2014

Reporting Precipitation on 1 July 2014 PRISM Stations Reporting Precipitation on 1 July 2014

PRISM daily rainfall map for the SE US on July 1, 2003 PRISM-Radar Mapping East of the Rockies, PRISM uses NOAA weather radar to provide detailed rainfall information between stations, resulting in a more precise and accurate picture of rainfall patterns than would be possible with station data alone. PRISM daily rainfall map for the SE US on July 1, 2003 = Station Heavy rain cell Stations Only Stations + Radar

Accepted Technology PRISM climate mapping technology has been continuously developed, and repeatedly peer-reviewed, since 1991. Seminal paper introducing PRISM (1994) has been cited in over 2,200 peer-reviewed journal articles; 6,700 PRISM citations in the scientific literature The impact of PRISM on the scientific community and the public good was recognized in 2004 when Daly was awarded “Outstanding Contribution to the Advance of Applied Meteorology” by the American Meteorological Society.

PRISM Data Usage PRISM data are available via public website http://prism.oregonstate.edu PRISM gridded data packages are downloaded about 35,000 times per day (1 million/month), making PRISM the most heavily used weather & climate mapping service in the country NOAA, NASA, USGS and USDA are among the US government’s largest PRISM data users PRISM data are used in a broad range of applications in agriculture, hydrology, engineering, ecology, economics, retail, and many, many more.

2012 USDA Plant Hardiness Zone Map The PRISM Climate Group was chosen to author the 2012 USDA Plant Hardiness Zone map, which receives about ½ million visits per month. It is likely the most heavily used climate map in the world.

Spatial Weather Forecasts Guided by PRISM PRISM datasets have been trusted by the National Weather Service and the Weather Channel, two of the county’s largest weather forecast providers, to guide the spatial patterns of their forecasts.

NOAA Extreme Precipitation Atlas The PRISM Climate Group is the mapping partner for the new NOAA Atlas 14 on extreme precipitation. The atlas is the official source for major storm precipitation data and is consulted by engineers in projects involving hydraulic design and drainage systems. PRISM map of the greatest 60-minute rainfall expected to occur once every 2 years, SE US