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This dataset contains the real time daily gridded precipitation analysis over 
the US. The analysis began on April 7, 1997 and continues to the present time.
The following information pertains to the dataset:


(1)Data Sources: River Forecast Center: ~6000 gauge stations per day and
                 Climate Anomaly Data Base: ~several hundred gauge stations 
                 per day 

(2) Resolution:  From April 7, 1997 to March 3, 1998, the resolution of the 
                 data is 1 degree longitude by 1 degree latitude, and the
                 file naming convention is "yyyymmdd.ll_stdqc".
		 Since March 4, 1998, the resolution of the analysis is 0.25
                 degree longitude by 0.25 degree latitude, and the file naming
                 convention is changed to "yyyymmdd.ll_stdqc_new".

(3) Domain:      The domain of the analysis is (140W-60W, 20N-60N). The first 
		 grid point is (140W, 20N), the second one is (139.75W, 20N), 
                 ... , and the last one is (60W, 60N).

(4) Window:	 Day 1 analysis is valid for the window from 12Z on day 0 to
                 12Z on day 1.

(5)Anal. Scheme: Modified Cressman (1959) Scheme (Glahn et al. 1985; Charba 
                 et al. 1992). 

(6)Quality Control: A. Duplicate Station Check
                    B. Data Check ( buddy check, standard deviation check 
                       against climatology )
                    C. NEXRAD Radar check for spurious zeros

(7) 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.


Users who use GrADS will also find the file "usdp.ctl" very useful because it 
contains all information about the data. 

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The file "usdp.ctl" is provided below.

dset ^19980712.ll_stdqc_new
title Real Time Daily Precipitation/Temperature Analysis and Monitoring
options sequential big_endian
undef 9999. 
xdef   321 linear   -140.000  0.25
ydef    161 linear  20.000  0.25 
zdef 1 linear  1 1
tdef 1 linear 01jan97 1dy
vars 1
p   0 0 daily precip  (inch)
ENDVARS