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Validation of Satellite-Derived Rainfall Estimates andNumerical Model Forecasts of Precipitation over the US
John Janowiak Climate Prediction Center/NCEP/NWS
2nd Int’l Precipitation Working Group - October 26, 2004
Work is modeled after the pioneering effort of Dr. Beth Ebert (BMRC/Australian BOM)
www.bom.gov.au/bmrc/wefor/staff/eee/SatRainVal/dailyval_dev.html
U.S. Validation at:
www.cpc.ncep.noaa.gov/products/janowiak/us_web.shtml
Validation Data Set
- 7000+ station reports daily
- 06Z – 06Z accumulation period
- Data analyzed using a Cressman-type scheme
- Error characteristics of validation data are NOT known
- Validation area matched for all estimates
(if missing in one, made missing in all)
Typical Station Distribution
CPC gauge analysis ( Aug 2003)CPC gauge analysis ( Aug 2003)
CMORPH analysis ( Aug 2003)CMORPH analysis ( Aug 2003)
CMORPH with evap. adjustmentCMORPH with evap. adjustment
Contribution to June 2004 Total Rainfall by Daily Rainfall Amount
Heaviest 10% of daily rainfall events
CONCLUSIONS
1. Merging PMW & IR estimates provides more accurate estimates ofprecipitation than the separate components can
CONCLUSIONS
1. Merging PMW & IR estimates provides more accurate estimates ofprecipitation than the separate components can
2. Two major systematic biases are apparent in the satellite estimates:a. OVERestimation over snow-covered regionsb. OVERestimation in semi-arid regions during the warm season
CONCLUSIONS
1. Merging PMW & IR estimates provides more accurate estimates ofprecipitation than the separate components can
2. Two major systematic biases are apparent in the satellite estimates:a. OVERestimation over snow-covered regionsb. OVERestimation in semi-arid regions during the warm season
3. NWP forecasts generally outperform blended satellite estimates and radar during the winter season over the U.S.
CMORPH vs. gauge over ‘NAME*’ zones
*North American Monsoon Experiment (2004)
CPC gauge analysis ( Aug 2003)CPC gauge analysis ( Aug 2003)
CMORPH analysis ( Aug 2003)CMORPH analysis ( Aug 2003)
Distribution of Daily Precipitation Amounts for June 2004
45 50 55 60 65 70 75 80 85 90 >90
