Land
Surface
Parameters
LDAS Precipitation Weighting Mask
A blended precipitation product is used to force LDAS LSMs. This product is derived by combining 3 hourly ETA model precipitation with hourly StageIV doppler radar precipitation and daily rain gauge preciptiation. Rain gauge and doppler radar coverage i
s sparse over Canada and Mexico, so it was decided that ETA model precipitation (without StageIV and Gauge information) would be used in these regions. Rather than have an abrupt cutoff at the United States border, a two degree wide blending area was set
tled upon. In this region, precipitation forcing consists of a weighted combination of pure ETA precipitation, and the merged ETA/StageIV/Gauge product mentioned above. The mask available below can be used to produce the final precipitation forcing fiel
d taking into account this 1 degree blending area.
LDAS Precipitation Blending Mask (Ascii)
* Use Right Mouse Button to Download *
The following mask file contains one weighting value per 1/8th degree grid box, with gridpoint (1,1) located at the lower left of the LDAS grid. A value of 0 indicates that you should only use ETA precipitation and should not use any StageIV or Ga
uge data. A value of 16 indicates that you should only use the blended ETA/StageIV/Gauge product. Values between 16 and 0 indicate that a combination of ETA and ETA/StageIV/Gauge data should be used. For example:
If the mask file has a value of 16 then....
Final Precip Forcing Field = 16/16*ETA/StageIV/Gauge + 0/16*ETA precipitation
If the mask file has a value of 5 then....
Final Precip Forcing Field = 5/16*ETA/StageIV/Gauge + 11/16*ETA precipitation
If the mask file has a value of 0 then....
Final Precip Forcing Field = 0/16*ETA/StageIV/Gauge + 16/16*ETA precipitation
The files can be read with the following statements:
real precipmask(464,224)
open (unit=10,file='precipmask.1deg.txt',status='old')
do j=1,224
do i=1,464
read(10,40) precipmask(i,j)
enddo
enddo
40 format(f4.1)
end
Precipitation Blending Mask (precipmask.1deg.txt)
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