PRISM Approach to Producing Analysis of Record Christopher Daly, Ph.D., Director Spatial Climate Analysis Service Oregon State University Corvallis, Oregon, USA

Spatial Climate Analysis Service Mission Service Provide innovative, state-of-the science spatial climate products and services to clients worldwide Research Maintain scientific research and development programs that provide the basis for products and services Education Advance “geospatial climatology” as an emerging discipline

SCAS and PRISM are Unique SCAS is the only center in the world dedicated solely to the mapping of climate PRISM climate mapping technology has been continuously developed, and repeatedly peer-reviewed, since 1991 PRISM climate maps are the “gold standard” by which others are evaluated SCAS has become a leader in climate mapping products and technology worldwide

- -Generates gridded estimates of climatic parameters (e.g., P, T, DP) - -Moving-window regression of climate vs. elevation for each grid cell -Uses nearby station observations - - Spatial climate knowledge base weights stations in the regression function by their climatological similarity to the target grid cell PRISM Parameter-elevation Regressions on Independent Slopes Model

PRISM KBS accounts for spatial variations in climate due to: -Elevation -Terrain orientation – rain shadows -Terrain profile – orographic enhancement -Moisture regime – trajectory model -Coastal proximity – trajectory model -Two-layer atmosphere – inversion layer, free atmosphere -Topographic position – susceptibility to cold air pooling PRISM Parameter-elevation Regressions on Independent Slopes Model

PRISM Moving-Window Regression Function Mean April Precipitati on, Qin Ling Mountains, China Weighted linear regression

Rain Shadows: Mean Annual Precipitation Oregon Cascades Portland Eugene Sisters Redmond Bend Mt. Hood Mt. Jefferson Three Sisters N 350 mm/yr 2200 mm/yr 2500 mm/yr Dominant PRISM KBS Components Elevation Terrain orientation Terrain profile Moisture Regime

Coastal Effects: July Maximum Temperature Central California Coast Monterey San Francisco San Jose Santa Cruz Hollister Salinas Stockton Sacramento Pacific Ocean Fremont N Preferred Trajectories Dominant PRISM KBS Components Elevation Coastal Proximity Inversion Layer 34 ° 20 ° 27 ° Oakland

Inversions – January Minimum Temperature Central Colorado Dominant PRISM KBS Components Elevation Topographic Index Inversion Layer Gunnison Lake City Crested Butte Taylor Park Res. -18°C -13 ° -18 ° N

US and W Canada mean monthly climate grids (NRCS, EC) Used in thousands of applications NWS RFC Mountain Mapper NWS MDL/MOS Experimental Gridded Forecasts Heavily peer-reviewed Official USDA digital climate layers All 50 states, plus YT,BC,AB,SK,MB Tmin, Tmax, Precip ( update for CONUS) 4-km resolution Relevant PRISM Datasets Available Now

Sequential monthly climate grids (NOAA, USFS) “Monthly version of Analysis of Record” Jan 1895 – present (ongoing project) CONUS Tmin, Tmax, Precip, Dew Pt 4-km resolution Current methodology uses mean monthly grids as predictors Relevant PRISM Datasets Available Now

Hi-res mean monthly climate grids (NRCS, NPS, USFS) All states/territories but Alaska (not funded) Tmin, Tmax, Precip m resolution or better Expected completion 2005 Relevant PRISM Datasets Under Development 800m 4 km

Suggested Methods “PRISM Climatologically Aided Interpolation” (CAI)  Most spatial patterns are repeatable, no need to construct them from scratch every time  Uses a high-quality mean climatology as the predictor grid, rather than a DEM  Highly robust to varying data density  Method is proven and operational Variant of CAI: “PRISM Model Aided Interpolation” (MAI) Not attempted, yet  High-resolution numerical model output used as predictor grid  PRISM acts as a sophisticated data assimilation tool

Suggested Improvements  Use climatologies that are “targeted” to better match current pattern  Use forecast or analysis model grids output to identify large-scale pattern  Select predictor grid with best pattern match  NWS Western Region is interested in developing targeted climatologies for Mountain Mapper  In central and eastern US, use radar and satellite precip estimates as ancillary predictive data for PRISM

Q & A What basic met variables have been mapped with PRISM?  Temp, Precip, Dew Pt, Solar Radiation  Wind speed and direction have not been mapped 12-day accumulated precip, Dec 1-12, 1999, western Oregon Is a daily or sub-daily Analysis of Record feasible with PRISM? Generally, yes Daily mapping of T,P,DP,SR performed successfully for western Oregon Biggest problem is variable time of obs (COOP) for precip. In plains and eastern US, using radar and satellite precip estimates as ancillary predictive data for PRISM would be helpful

Q & A Can daily or sub-daily observations be QC’ed with PRISM technology?  Yes, we are developing a spatial, probabilistic QC system for NRCS’ daily SNOTEL data What is a ballpark cost for developing a daily retrospective Analysis of Record using current PRISM methods?  $ K  Tmax, Tmin, Ppt, Dew Pt  Jan Dec 2003 (or more recent)  CONUS, 4-km grid resolution  Enhancements and scheduled updates extra

OSU SCAS Web Site Near real time monthly maps for US Long-term average maps Graphics, map server, and data