[gradsusr] NAM and APCPSFC data

[Mark Sponsler]

Hi,I'm trying to display variable 'apcpsfc' from the 3 hr and 1 hr NAM.  The resulting images appear to pulsate/accumulate precip every few images then reset only to accumulate again.I've seen the threads in the archive on this issue with HD GFS data, but I'm trying to understand 2 things:1) What is the accumulation period for NAM 1 hr and 3 hr data.  I was thinking it was every 3 time steps (i.e. excluding time step 1 / 00 hr), it is 2, 3, 4 then reset and start accumulating again for the next 3 time steps 5, 6 and 7).  But that doesnt seem to be the case. 2) What does it mean to 'normalize' the data? Westly did something in wgrib2 for HD GFS data to normalize it and I was wondering if that was also applicable to NAM data.  What is done to mathmatically to get the data to be valid for just a single timestep?.  Can I write something in GRDADS to perform the normalization rather than having to use WGRIB2. Assuming the accumulation theory is correct (that apcpsfc accumulates every three time steps), I've been trying to write code to remove the accumulation by:Display Time = 2Time 3 = Time 3 - Time 2Display Time 3Time 4 = Time 4 - Time 3Display Time 4But it doesnt work. Any help would be appreciated.Thanks,Mark        


Thanks,Mark
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