Precipitation Climatology and Mapping in the United States

1. Precipitation Climatology and Mapping in the United States Christopher Daly Director Spatial Climate Analysis Service Oregon State University Corvallis, Oregon

2. Outline • Precipitation climatology • PRISM overview • PRISM map products

3. Issues of Scale(Spatial and Temporal) • Over long averaging times (say, the 30 year normal maps), only the most important and consistent meteorological factors are evident • Progressively shorter time spans reveal ever-increasing nuances of the atmospheric system

4. Instantaneous

7. Characteristics of the Mean Precipitation Climate • The principal controlling factors are the availability of atmospheric moisture and lifting mechanisms • Moisture controlled by flow from and proximity to large water bodies • Propensity for lifting influenced by topography, convergence zones (seabreeze, etc.), preferred storm tracks (jet dynamics)

8. Orographic Precipitation Enhancement Factors • Atmospheric Moisture • Precipitable water • Vertical distribution of moisture • Terrain blocking capability • “Footprint” • Steepness • Orientation

27. PRISM Spatial Climate Modeling System • PRISM (Parameter-elevation Regressions on Independent Slopes Model) • Knowledge-based system using point data, digital elevation model, & other spatial data sets • Generates gridded estimates of climatic parameters (such as precipitation & temperature) • Accounts for rain shadows, inversions, coastal proximity, and others

29. Form of Grid Cell Prediction • Y = 1X + 0 , where Y is the predicted climate element and X is the DEM elevation at the target cell. 0 and 1 are regression slope and intercept, and are determined by x,y pairs of elevation and climate observations from nearby climate stations

30. Station Weighting • Combined weight of a station is: W = f {Wd, Wz, Wc, Wl, Wf, Wp, We} , where Wd, Wz, Wc, Wl, Wf, Wp, We are the distance, elevation, cluster, vertical layer, topographic facet, coastal proximity and effective terrain height weights.

33. Olympic Mtns Annual Precipitation Facets On + Vertical Extrapolation On Inches

34. Olympic Mtns Annual Precipitation Facets On + Vertical Extrapolation Off Inches

35. Olympic Mtns Annual Precipitation Facets Off + Vertical Extrapolation Off Inches

36. Olympic Mtns Annual Precipitation No elevation Inches

37. Olympic Mtns Annual Precipitation Facets On + Vertical Extrapolation On Inches

39. Some SCAS Projects Project US Precip & temp US Climate Atlas - 40 elements US 103-yr precip & temp Canada precip & temp China/Mongolia precip & temp WA, OR, CA, BC precip intensity BC PMP analysis PNW flood analysis SW and OH Precip frequency US R-factor and EI10 Client USDA NRCS NOAA NCDC NASA & NOAA OGP Environment Canada, BC USDA, OR WA DOT, OR WRD, BC Hydro BC Hydro USDA Forest Service NWS-HDSC USEPA

41. Cartographic-quality Map of Mean Annual Precipitation for Idaho Produced at the USDA-NRCS NCGC

42. PRISM Product Dissemination • Hardcopy maps Cartographic-quality, walls-size maps of mean annual precipitation for each state Available from the NRCS Climate Data Liaison in each state or OSU SCAS **Sign-up sheet

43. PRISM Precipitation Product Dissemination • Compact Discs All precipitation layers for all of the U.S. 3 CD’s (East, Central, West) of the lower 48 states. Includes Arc Explorer viewing software, and all documentation. Available from the NRCS-NCGC: 800-672-5559

44. PRISM Precipitation Product Dissemination • Digital via Web Sites SCAS: www.ocs.orst.edu/prism/ NRCS: www.ftw.nrcs.usda.gov/prism/prism.html

45. Oregon Annual Precipitation

48. All PRISM gridded products to date available on CD from:

49. Hydrometeorological Design Studies Center (HDSC) of the NWS:http://www.nws.noaa.gov/oh/hdsc/index.html

50. Oregon Annual Precipitation