The Evaluation of a Passive MicrowaveBased Satellite Rainfall Estimation Algorithm with an IRBased A

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CPC Morphing Technique
The Evaluation of a Passive Microwave-Based
Satellite Rainfall Estimation Algorithm with an
IR-Based Algorithm at Short time Scales
Robert Joyce RS Information Systems John
Janowiak Climate Prediction Center/NCEP/NWS Philli
p Arkin ESSIC University of
Maryland Pingping Xie Climate Prediction
Center/NCEP/NWS
2nd International Precipitation Working Group
October 25-28, 2004
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Outline

• 1. CMORPH concept
• 2. CMORPH methodology
• 3. Validation
• 4. Improvement potential and future work
• 5. Conclusions

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CMORPH is not a precipitation estimation
technique but rather a method that creates
spatially temporally complete information using
existing precipitation products that are derived
from passive microwave observations.
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TMI rainfall estimates from NASAs 2A12 algorithm
(Kummerow et al., 1996) Goddard Profiling (GPROF)
version 5, soon version 6 AMSR-E precipitation
estimates from GPROF-6 rainfall algorithm run at
NOAA/NESDIS/ORA. SSMI precipitation estimates
from NOAA/NESDIS/ORA GPROF-6 SSMI rainfall
algorithm. AMSU-B rainfall estimates from new
NESDIS/ORA AMSU-B rainfall algorithm (Weng et
al., 2003)
Half hourly, 0.0727 lat/lon (8 km at equator)
resolution arrays (separate for each sensor type)
are assigned the nearest rainfall estimate within
swath regions Averaging of retrieval estimates
within same grid points (AMSR-E and TMI only)
Anomalous microwave estimated rainfall screened
with NESDIS Satellite Services Division (SSD)
daily Interactive Multi-sensor Snow and Ice
Mapping System (IMS) product
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• PMW rainfall gridded to 8km resolution

3-hr mosaic good coverage but time of obs.
varies by 3 hrs
MANY thanks to NESDIS/OSDPD R. Ferraro
(NESDIS/ORA)
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• PMW rainfall gridded to 8km resolution

3-hr mosaic good coverage but time of obs.
varies by 3 hrs
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IR Data

• All 5 geostationary meteorological satellites
• Obtained via McIDAS
• Merged into ½ hr global (60N-60S), 4 km maps
• Corrections for limb darkening parallax
  applied

Refs Janowiak et al., Bull. Amer. Meteor. Soc.,
Feb 2001) Joyce et al., J. Appl.
Meteor., Apr 2001 Most recent 8 days (each ½ hr
period) available at ftpprd.noaa.gov
pub/precip/global_full_res_IR
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Advection Vector Components
Zonal
Meridional
20Z March 7, 2004
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Hourly Rainfall during 06UTC to 23UTC on Oct 5,
2003
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Satellite - CPC gauge analysis Merged PMW
only Radar Difference from gauge analysis
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Satellite - CPC gauge analysis CMORPH
Radar Difference from gauge analysis
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Comparison with U.S. Gauge Analyses
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• DJF 2003-2004 statistics using Australian Bureau
  of Meteorology 0.25 degree lat/lon daily rain
  gauge analyses for validation
• Red line CMORPH
• Blue line Merged PMW
• Black gauge analyses

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Limitations

• Present estimation algorithms cannot retrieve
  precip. over snow or
• ice covered surfaces
• - New algorithms being developed (Liu, Ferraro)
• Data Latency 18 hours past real-time
• Will not presently detect precip. that develops,
  matures decays
• between microwave scans
• Limits on how far back data can be processed
  early 1990s?

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• Hourly, 0.25 degree lat/lon CMORPH timestamp 1
  (30 minutes from nearest PMW scan) correlation
  with Stage II radar rainfall (top panel)
• Hourly, 0.25 degree lat/lon IR-based PMW/IR
  combined frequency matching rainfall estimation
  (IRFREQ) correlation with Stage II radar rainfall
  (2nd from top)
• CMORPH radar rainfall correlation minus IRFREQ
• Correlation pair counts

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• Hourly, 0.25 degree lat/lon CMORPH timestamp 2
  (60 minutes from nearest PMW scan) correlation
  with Stage II radar rainfall (top panel)
• Hourly, 0.25 degree lat/lon IRFREQ correlation
  with Stage II radar rainfall (2nd from top)
• CMORPH radar rainfall correlation minus IRFREQ
• Correlation pair counts

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• Hourly, 0.25 degree lat/lon CMORPH timestamp 3
  (90 minutes from nearest PMW scan) correlation
  with Stage II radar rainfall (top panel)
• Hourly, 0.25 degree lat/lon IRFREQ correlation
  with Stage II radar rainfall (2nd from top)
• CMORPH radar rainfall correlation minus IRFREQ
• Correlation pair counts

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• Hourly, 0.25 degree lat/lon CMORPH timestamp 4
  (120 minutes from nearest PMW scan) correlation
  with Stage II radar rainfall (top panel)
• Hourly, 0.25 degree lat/lon IRFREQ correlation
  with Stage II radar rainfall (2nd from top)
• CMORPH radar rainfall correlation minus IRFREQ
• Correlation pair counts

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• The cumulative percentage of half hourly periods
  sampled for an eight day period, in 30 minute
  increments to nearest past/future scan,
  instantaneous (timestamp 0, top)
• cumulative sampled within 30 minutes of half
  hourly frame (timestamp
• cumulative sampled within 60 minutes of half
  hourly frame (timestamp

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• Half hourly, 0.25 degree lat/lon CMORPH
  correlation against withheld MWCOMB rainfall 23
  June 6 August 2004. Temporal distance of
  CMORPH to nearest PMW scan 30 minutes
  (timestamp 1, top)
• Half hourly, 0.25 degree lat/lon IRFREQ
  correlation against withheld MWCOMB rainfall
  (timestamp 1, 2nd from top)
• CMORPH correlation minus IRFREQ (3rd from top)
• of correlation pairs (bottom)

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• Half hourly, 0.25 degree lat/lon CMORPH
  correlation against withheld MWCOMB rainfall,
  temporal distance of CMORPH to nearest PMW scan
  60 minutes (timestamp 2, top)
• Half hourly, 0.25 degree lat/lon IRFREQ
  correlation against withheld MWCOMB rainfall
  (timestamp 2, 2nd from top)
• CMORPH correlation minus IRFREQ (3rd from top)
• of correlation pairs (bottom)

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• Half hourly, 0.25 degree lat/lon CMORPH
  correlation against withheld MWCOMB rainfall,
  temporal distance of CMORPH to nearest PMW scan
  90 minutes (timestamp 3, top)
• Half hourly, 0.25 degree lat/lon IRFREQ
  correlation against withheld MWCOMB rainfall
  (timestamp 3, 2nd from top)
• CMORPH correlation minus IRFREQ (3rd from top)
• of correlation pairs (bottom)

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• Half hourly, 0.25 degree lat/lon CMORPH
  correlation against withheld MWCOMB rainfall,
  temporal distance of CMORPH to nearest PMW scan
  120 minutes (timestamp 4, top)
• Half hourly, 0.25 degree lat/lon IRFREQ
  correlation against withheld MWCOMB rainfall
  (timestamp 4, 2nd from top)
• CMORPH correlation minus IRFREQ (3rd from top)
• of correlation pairs (bottom)

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Daily times series of correlation comparing
IRFREQ, CMORPH, and CMORPH-IR 0.25 degree lat/lon
rainfall estimates with same high-quality rain
gauge and radar analyses over the U.S. for the 7
May 27 July 2004 period. IRFREQ blue
lines CMORPH green lines CMORPH-IR red
lines
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FUTURE WORK

• Improve accuracy of CMORPH PMW rainfall vectors
• Continue to investigate model winds GMORPH
• Continue investigation into the development of
  CMORPH IR

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Further Information
The End Thank You