XPRATE
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This is how precipitation was corrected to give XPRATE.

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Here's the correction of daily precipitation amounts.

1) COMPUTE MOISTURE SOURCE
  Compute the source of moisture due to the correction term in the diffusion
  of moisture.  This moisture source is assumed to be constant in time.
  [wne: spurious moisture sinks were ignored]

2)  ADJUST MOISTURE SOURCE
  Read in the daily precipitation rate and average daily two-meter temperature.
  The moisture source is zeroed out where the temperature is above 10 C;
  its full value is used where the temperature is below 0 C; and a fraction
  of its value is used where the temperature is between 0 and 10 C.

3)  REMOVE MOISTURE SOURCE
  The projection of the precipitation onto the adjusted moisture source
  is computed and removed from the precipitation rate.  Calibration runs
  indicated that the spurious precipitation was removed when
  70% of the moisture source term was removed from the precipitation rate.
  The precipitation rate is not allowed to become negative. 


                          Bob Kistler     (wd23bk@sun1.wwb.noaa.gov)
                          Mark Iredell    (wd20mi@sun1.wwb.noaa.gov)