Hi Ferret users
I am using a mask at 15" resolution and I calculate the area in km2 with @DIN operator
use mask_15s ! variable=mask with 0 and 1
set var/bad=0 mask ! 0 is defined as missing value
list mask[x=@din, y=@din] / 1.E06 ! surface in km2
the result is correct : 15805. km2
Now I regrid the mask to 1mn:
let ma0 = mask[gxy=GIN1]
and re-compute integral:
list ma0[x=@din, y=@din] / 1.E06
the result is: 1.695E-06 , so the surface is not the same.
What happens during the regriding % @DIN operator ?
Thanks
characteristics of variable mask:
GRID GAP1
name axis # pts start end
LONGITUDE LONGITUDE 1020mr 75.502E(75.502) 79.748E(79.748)
LATITUDE LATITUDE 480 r 41.419N 43.415N
LEVEL2 Z (level) 1 r- 0 0
TIME3 T (time) 1 r 0 0
normal E
normal F
stat mask
MASK
LONGITUDE: 75.5E(75.5) to 79.8E(79.8)
LATITUDE: 41.4N to 43.4N
Z (level): 0
T (time): 0
E: N/A
F: N/A
DATA SET: mask_15s.nc
Total # of data points: 489600 (1020*480*1*1*1*1)
# flagged as bad data: 389847
Minimum value: 1
Maximum value: 1
Mean value: 1 (unweighted average)
Standard deviation: 0
characteristics of variable ma0
GRID GIN1
name axis # pts start end
LON X 206 r 75.917 79.333
LAT Y 76 r 41.75 43
LEVEL Z 1 r 0 0
M2 TIME 168 r 16-JAN-2001 05:14 17-DEC-2014 04:14
normal E
normal F
stat ma0
MASK[GXY=GIN1]
X: 75.9 to 79.3
Y: 41.7 to 43
Z (level): 0
T (time): 0
E: N/A
F: N/A
DATA SET: mask_15s.nc
Total # of data points: 15656 (206*76*1*1*1*1)
# flagged as bad data: 9555
Minimum value: 1
Maximum value: 1
Mean value: 1 (unweighted average)
Standard deviation: 0
> Francois DELCLAUX> ------------------------------------------------------------> UMR HydroSciences - CC 57> Université Montpellier> 163 rue Auguste Broussonnet> 34090 Montpellier FRANCE> > http://www.hydrosciences.org/> mailto: francois.delclaux@xxxxxxxxxxxxxxxxxxx> Tel : (33) (0)4 67 14 90 11 Fax : (33) (0)4 67 14 47 74> ------------------------------------------------------------
--
François DELCLAUX
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UMR HydroSciences - CC 57
Université Montpellier
163 rue Auguste Broussonnet
34090 Montpellier FRANCE
http://www.hydrosciences.org/
mailto: francois.delclaux@xxxxxxxxxxxxxxxxxxx
Tel : (33) (0)4 67 14 90 11 Fax : (33) (0)4 67 14 47 74
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