The PRISM Approach to Mapping Climate in Complex Regions

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The PRISM Approach to Mapping Climatein Complex
Regions

• Christopher Daly, Ph.D., Director
• Spatial Climate Analysis Service
• Dept. of Geosciences, College of Science
• College of Oceanographic and Atmospheric Sciences
• Oregon State University
• Corvallis, Oregon, USA

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• Outline
• Rational behind PRISM approach
• How PRISM works
• Some useful PRISM data sets

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Oregon Annual Precipitation
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Oregon Annual Precipitation
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Oregon Annual Precipitation
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Oregon Annual Precipitation
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Oregon Annual Precipitation
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Rationale

• Observations are rarely sufficient to completely
  represent the spatial patterns of climate,
  requiring intelligent interpolation
• Human-expert mapping methods often produce the
  best products, but are slow, inconsistent, and
  non-repeatable
• Purely statistical mapping methods are fast and
  repeatable, but rarely provide the best accuracy,
  detail, and realism

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Rationale

• Therefore
• The best method may be a statistical approach
  that is fast and automated, but developed, guided
  and evaluated with expert knowledge

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Knowledge-Based System KBS

• Knowledge acquisition capability Elicit expert
  information
• Knowledge base Store of knowledge
• Inference Engine Infer solutions from stored
  knowledge
• User interface Interaction and explanation
• Independent verification Knowledge refinement

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PRISM
Parameter-elevation Regressions on Independent
Slopes Model

• Generates gridded estimates of climatic
  parameters
• Moving-window regression of climate vs. elevation
  for each grid cell
• Uses nearby station observations
• Spatial climate knowledge base weights stations
  by their physiographic similarity to the target
  grid cell

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Oregon Annual Precipitation
Interface
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PRISM
Knowledge Base

• Elevation Influence on Climate

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1961-90 Mean January Precipitation, Sierra
Nevada, CA, USA
Oregon Annual Precipitation
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1961-90 Mean August Max Temperature, Sierra
Nevada, CA, USA
Oregon Annual Precipitation
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1963-1993 Mean November Precipitation, Puerto Rico
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1963-95 Mean June Maximum Temperature, Puerto Rico
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1971-90 Mean February Precipitation, European Alps
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1961-90 Mean September Max Temperature, Qin Ling
Mountains, China
Oregon Annual Precipitation
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PRISM Moving-Window Regression Function
Oregon Annual Precipitation
1961-90 Mean April Precipitation, Qin Ling
Mountains, China
Weighted linear regression
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Governing Equation

• Moving-window regression of climate vs
  elevation
• y ?1x ?0
• Y predicted climate element
• x DEM elevation at the target cell
• ?0 y-intercept
• ?1 slope
• x,y pairs - elevation and climate observations
  from nearby climate stations

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Station Weighting

• Combined weight of a station is
• W f Wd , Wz , Wc , Wf , Wp , Wl , Wt , We

• Distance
• Elevation
• Clustering
• Topographic Facet (orientation)

• Coastal Proximity
• Vertical Layer (inversion)
• Topographic Index (cold air pooling)
• Effective Terrain Height (orographic profile)

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PRISM
Knowledge Base

• Terrain-Induced Climate Transitions (topographic
  facets, moisture index)

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Rain Shadow Mean Annual Precipitation Oregon
Cascades
Portland
Mt. Hood
Eugene
Mt. Jefferson
2500 mm/yr
2200 mm/yr
Sisters
Three Sisters
350 mm/yr
Redmond
N
Bend
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1961-90 Mean Annual Precipitation, Cascade Mtns,
OR, USA
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1961-90 Mean Annual Precipitation, Cascade Mtns,
OR, USA
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Olympic Peninsula, Washington, USA
Flow Direction
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Topographic Facets
? 4 km

? 60 km

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Mean Annual Precipitation, 1961-90
Oregon Annual Precipitation
Max 7900 mm
Full Model
3452 mm 3442 mm 4042 mm Streamflow
Max 6800 mm
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Mean Annual Precipitation, 1961-90
Max 4800 mm
3452 mm 3442 mm 4042 mm Streamflow
Facet Weighting Disabled
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Mean Annual Precipitation, 1961-90
Oregon Annual Precipitation
Max 3300 mm
3452 mm 3442 mm 4042 mm Streamflow
Elevation 0
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Mean Annual Precipitation, 1961-90
Oregon Annual Precipitation
Max 7900 mm
Full Model
3452 mm 3442 mm 4042 mm Streamflow
Max 6800 mm
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PRISM
Knowledge Base

• Coastal Effects

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Coastal Effects 1971-00 July Maximum
Temperature Central California Coast
Sacramento
Stockton
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San Francisco
Oakland
Fremont
San Jose
Preferred Trajectories
Santa Cruz
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Pacific Ocean
Hollister
Monterey
Salinas
N
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1961-90 Mean July Maximum Temperature, Central
California, USA
Coastal Proximity Weighting OFF
Coastal Proximity Weighting ON
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PRISM
Knowledge Base

• Two-Layer Atmosphere and Topographic Index

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1971-2000 January Temperature, HJ Andrews Forest,
Oregon, USA
TMAX-Elevation Plot for January
Layer 1 Layer 2
TMIN-Elevation Plot for January
Layer 1 Layer 2
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Mean Annual Precipitation, Hawaii
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United States Potential Winter Inversion
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Western US Topographic Index
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Central Colorado Terrain and Topographic Index
Gunnison
Gunnison
Terrain
Topographic Index
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January Minimum Temperature Central Colorado
Gunnison
Gunnison
Valley Bottom Elev 2316 m Below Inversion Lapse
5.3C/km T -16.2C
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January Minimum Temperature Central Colorado
Gunnison
Mid-Slope Elev 2921 m Above Inversion Lapse
6.9C/km T -12.7C
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January Minimum Temperature Central Colorado
Gunnison
Ridge Top Elev 3779 m Above Inversion Lapse
6.0C/km T -17.9C
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Inversions 1971-00 January Minimum Temperature
Central Colorado
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Dominant PRISM KBS Components Elevation
Topographic Index Inversion Layer
Taylor Park Res.
Crested Butte
-18
Gunnison
-13
-18C
Lake City
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PRISM 1971-2000 Mean January Minimum Temperature,
800-m
Banana Belt
Cold air drainage
Snake Plain
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Inversions 1971-00 July Minimum Temperature
Northwestern California
Pacific Ocean
N
Willits
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Dominant PRISM KBS Components Elevation
Inversion Layer Topographic Index Coastal
Proximity
Ukiah
Lake Pilsbury.
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Cloverdale
Lakeport
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Clear Lake
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PRISM
Knowledge Base

• Orographic Effectiveness of Terrain

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United States Effective Terrain
United States Orographically Effective Terrain
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Oregon Annual Precipitation
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PRISM
Knowledge Base

• Explanatory power of climatic patterns, or
  climatologically-aided interpolation (CAI)

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Oregon Annual Precipitation
Leveraging Information Content of High-Quality
Climatologies to Create New Maps with Fewer Data
and Less Effort
Climatology used in place of DEM as PRISM
predictor grid
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PRISM Regression of Climate vs Climate or
Weather vs Climate
20 July 2000 Tmax vs 1971-2000 Mean July Tmax
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Official USDA 1961-90 Precipitation and
Temperature Maps for the US (NRCS)
1971-2000 hi-res update
4 km
Seamless coverage
0.8 km
Each state peer-reviewed
Used in thousands of applications
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1961-90 US Climate Atlas (NOAA NCDC)
Over 1,000 SCAS Maps
Built upon NRCS mapping project
PRISM Mean Annual Precipitation Hawaiian
Islands, 1961-90
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1895-Present Near Real-Time Monthly Climate Time
Series Updates (USFS, NOAA OGP, NASA)
Built upon NRCS, Atlas, and NOAA time series
projects
New maps created 7-14 days after end of month

• Wildfire Risk Assessment
• and Prediction
• Drought
• Water supply
• Climate variability

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Upcoming Products

• Updated 1971-2000 mean monthly P, Tmax, Tmin maps
  for the US at 800-m resolution (USDA-NRCS, NPS,
  USFS)
• Spatial-Probabilistic QC system for SNOTEL
  observations (USDA-NRCS)
• Targeted climatologies for NWS River Forecast
  Centers (NWS Western Region)
• Extreme precipitation frequency maps for regions
  in US (NWS HDSC)

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Future Directions

• Engage in collaborative projects to develop the
  use of PRISM and PRISM climatologies for
  downscaling weather analyses and predictions
• Continue to develop technology to move to smaller
  time steps and higher resolution
• Explore using remotely-sensed data to improve
  PRISM accuracy in under-sampled areas (and
  vice-versa)
• Continue to develop PRISMs Spatial Climate
  Knowledge Base

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PRISM Info and Data Set Access

www.ocs.oregonstate.edu/prism/www.climatesource.
com