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About the Analyses
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DATA SOURCE: River Forecast Centers ~5000 stations per day,
including ~1500 stations from the Hydrologic Automated Data System, and Climate Anomaly Data Base ~several hundred stations per day
RESOLUTION: 0.5 degree x 0.5 degree
DOMAIN: 20N - 60N; 140W - 60W
FORMAT: The format is sequential 32-bit IEEE floating point created on a big_endian platform
(e.g. cray, sun, sgi and hp). The undefined (missing) value is 9999.
WINDOW: Day 1 analysis is valid for the window from 12Z on day 0 to 12Z on day 1; because of
report receipt timing, daily minima are available 1 day earlier than the maxima and the means.
ANALYSIS SCHEME: Modified Cressman (1959) scheme (Glahn et al. 1985; Charba et al. 1992).
Minimum stations for analysis: 350. If the number of stations is fewer than the minimum, the analysis is
not performed for that day.
QUALITY CONTROL: Climatological standard deviation check. If a reported value is more than 4
standard deviations removed from the historical distribution, the value is omitted from the analysis.
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www.nws.noaa.gov 
