gis and drought applications keith stellman senior hydrologist lower mississippi river forecast...
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GIS and Drought GIS and Drought ApplicationsApplications
Keith StellmanKeith StellmanSenior HydrologistSenior Hydrologist
Lower Mississippi River Forecast CenterLower Mississippi River Forecast CenterSlidell, LASlidell, LA
OutlineOutline
• Overview of CPC products
• History/Background info/Examples
• Validity of the Data
• Gridded Normals?
• Compositing
• Possibilities
Overview / HistoryOverview / 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
Details, DetailsDetails, Details
• County to county rainfall surplus/deficits
• Grid to grid comparisons
• Water supply issues from county to county
RFC Observed AnalysisRFC 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
How Accurate is the Data?How Accurate is the Data?1 month totals for October 20021 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
What is Normal?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
Where Can I Find PRISM Data?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 DalyDirectorSpatial Climate Analysis ServiceOregon State UniversityCorvallis, Oregon
How do we get the resultsHow 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
Who is doing what?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
CompositeComposite
• 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