GIS and Drought Applications

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GIS and Drought Applications

• Keith Stellman
• Senior Hydrologist
• Lower Mississippi River Forecast Center
• Slidell, LA

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Outline

• Overview of CPC products
• History/Background info/Examples
• Validity of the Data
• Gridded Normals?
• Compositing
• Possibilities

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Normal CPC Drought Graphics
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CPC Graphics Cont
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CPC Graphics Cont.
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Overview / History

• Stage III
• 4 x 4 km resolution
• Gridded PRISM data
• ABRFC
• Computed daily average from PRISM data
• Posted output images to web
• LMRFC
• Converted prism grids to HRAP projection in GIS
• Computed monthly images on 1st of the month

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CPC Percent of Normal
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RFC Graphics1 Month Stage III
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RFC Graphics
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WGRFC/ABRFC/OHRFC Examples
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Detailed RFC Images
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Details, Details

• County to county rainfall surplus/deficits
• Grid to grid comparisons
• Water supply issues from county to county

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RFC Observed Analysis

• Daily rain gage analysis in GIS using IDW method
  of interpolation on 4x4 km grid
• Grids are archived
• Grids are summed for monthly totals
• Rain gage analysis can then be used for percent
  of normal

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Observed Analysis1 Month Totals
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LMRFC Observed Analysis
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Comparisons
Minimums
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How Accurate is the Data?1 month totals for
October 2002
ASOS ID Stage III Estimate Gage Analysis Estimate ASOS Monthly Total
LCH 21.02 21.45 21.27
LFT 17.43 18.27 18.35
AEX 14.19 12.49 13.37
LIT 5.14 5.09 5.07
MEM 8.49 8.28 8.41
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What is Normal?

• 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

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Orographic Enhancement
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PRISM Maps
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Where Can I Find PRISM Data?

• Digital via Web Sites
• SCAS www.ocs.orst.edu/prism/
• NRCS www.ftw.nrcs.usda.gov/prism/prism.html
• Contact Info
• Christopher Daly
• Director
• Spatial Climate Analysis Service
• Oregon State University
• Corvallis, Oregon

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How do we get the results

• PRISM data is on a 4x4 km grid
• Stage III data is on a 4x4 km grid
• ((((StageIII-Prism)/Prism)1)100) of Normal
  Precipitation
• GIS Software does grid calculations and exports
  result as a JPEG
• Program is automatically run on 1st of the month
  for previous 1,2,3 and 6 months

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Who is doing what?

• ABRFC,WGRFC,LMRFC,OHRFC,CBRFC
• Utilize gridded datasets
• CBRFC lists under water supply in form of pdf
  document
• MBRFC,NERFC and MARFC
• Utilize observed datasets on larger scale
• MBRFC uses pdf document under water supply

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Composite

• Southern Region RFC Web Team
• Goal is to composite graphics with levels of zoom
• Each SR RFC (SERFC,WGRFC,LMRFC,ABRFC) sends daily
  StageIII totals to WGRFC
• Data is summed into monthly totals and compared
  to PRISM data

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Coming Very Soon!
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Future Possibilities

• Providing each monthly calculation as a shapefile
  or ascii grid
• Incorporating more than SR RFCs into the
  datasets
• Utilizing gage only datasets across SR