WSR88D PRECIPITATION ESTIMATION FOR HYDROLOGIC APPLICATIONS

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WSR-88D PRECIPITATION ESTIMATION FOR HYDROLOGIC
APPLICATIONS DENNIS A. MILLER
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Enhancements to PPS

• Build 10 (Nov. 1998)
• Terrain Following Hybrid Scan
• Graphical Hybrid Scan
• Adaptable parameters appended to DPA
• Open Systems RPG
• Range Correction
• Mean Field Bias Correction

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Radar Precipitation Estimation Stage II and III
Processing
HDP 4 km res.
RFC
WFO
Stage II
Stage II
Rain gages
WHFS/FFMP
Stage III
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Stage II

• Processing for individual radars
• 4 km resolution on HRAP grid
• 131 x 131 array

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Stage II

• Mean field bias adjustment
• multisensor gage/radar merging
• gage only analysis

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Stage II processing

• Generally run once per hour at H15 mins for each
  radar using hourly rainfall ending at H00 min
• Updated every hour to incorporate late arriving
  gage data by (H115,H215 etc)

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Automated QC of HDP Data

• Removal of HRAP bin data that are consistently
  bad (e.g. Mountain blockage or ground clutter
  contamination)
• Removal of bin data contaminated by anomolous
  propagation (AP) though use of GOES IR satellite
  and surface temperature data
• Removal of outlier bin data (R gt threshold)

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Mean Field Bias Adjustment

• Attempts to account for uniform errors over the
  entire field such as radar calibration, improper
  Z-R relationship
• Bias is a function of current and previous hours
  bias
• Memory span parameter indicates how many hours to
  look into the past when determining the current
  bias

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Mean Field Bias Adjustment
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Single Optimal Estimation
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Stage II Multisensor Rainfall Field Generation
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Stage II
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Stage III

• Mosaics Stage II multisensor rainfall estimates
  on to larger HRAP grid
• Interactive Quality Control
• Can be used as main input into hydrologic models
  through (MAPX)

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Stage III Mosaic

• In areas that where more than one radar overlaps
  forecaster has choice
• mean value of overlapping bins
• maximum value of overlapping bins
• If multisensor field is not available for a given
  area, the gage only field is used

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Stage III interactive features

• Display geographic overlays
• Time Lapse
• Zoom
• Display and Edit Gages
• Add pseudo gages
• Delete AP
• Re-run Stage II and re-mosaic

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Important Adaptable Parameters

• Memory Span (1-1000)
• controls responsiveness of bias adjustment
• Indicator Cross Correlation Coefficient (0-1)
• controls how good radar verses gage is at
  indicating where it is raining
• Conditional Cross Correlation Coefficient (0-1)
• controls how good radar verses gage is at
  indicating amount of rainfall

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Case Study

• Site ABRFC
• Study impact of varying adaptable parameters
• Vary ICC (0-1)
• Vary CCC(0-1)
• Compare with 24 hour co-op gages
• Compare forecast with observed hydrograph

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Raw unadjusted Radar Estimate
Analysis of 24 hour co-op reports
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Bias Corrected Radar
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Multisensor
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WATTS RADAR ONLY WITH NO BIAS ADJUSTMENT
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WATTS GAGE ONLY
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WATTS RADAR ONLY WITH BIAS ADJUSTMENT
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WATTS MULTISENSOR ESTIMATE
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RFC-WIDE Multisensor Precipitation Estimation

• Mosaic of data from lowest available height
• Radar Climatology used to define blocked areas
• Optimal Estimation to fill missing areas using
  available gages and surrounding good radar data
• Satellite and Model Data to delineate clear air
  AP
• No radar data taken from above freezing level
  used
• PRISM data used to scale estimates in missing
  areas

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FCX frequency of rainfall
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FCX Coverage
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PBZ Total Rainfall Summer Months
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Summer Coverage
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PBZ Total Rainfall Winter Months
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Winter coverage
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HEIGHT OF COVERAGE
RADAR COVERAGE MAP
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RADAR COVERAGE MAP
PRECIPITATION MOSAIC
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BIAS ADJUSTMENT
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MULTISENSOR ESTIMATION FILLS MISSING AREAS
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MULTISENSOR ESTIMATION FILLS MISSING AREAS
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HURRICANE FLOYD RAINFALL
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SUMMARY AND CONCLUSIONS