Dear ferret users.
I want to calculate temporal
correlation between two datasets. Both datasets are area average values with equal number of time
steps but ferret is giving error when I tried to compute correlation between the two. My guess is there is inconsistency in unit of time dimension between the dataset which is causing the problem. But how can I overcome this?
==========
Below is my commands and ferret messages:
use HCIyear17.nc, j4pranom2.nc
sh d/f
currently SET data sets:
1> ./HCIyear17.nc
name title I J
K L
HCI V850ANOM-V200ANOM 1:1 1:1 1:1 1:17
on grid GTL1 with -1.000000E+34 for missing data
X=90.2E:91.2E Y=19.8N:20.8N Z=849.5:850.5
time range: 15-SEP-1989 21:00 to 15-SEP-2005 21:00
2> ./j4pranom2.nc (default)
name title
I J K L
J4PRANOM2
PRECIP[D=3]-J4PRCLM2 ... ... ... 1:17
(X=70E:90E@AV4, Y=6.2N:25N@AV4)
on grid GPA1 with -1.000000E+34 for missing data
time range: 30-SEP-1989 00:00 to 30-SEP-2005 00:00
let p=hci[d=1]; let q=j4pranom2[d=2]
go variance
...
list correl
...
**ERROR: illegal limits: Q is not in the range T=04-JAN-1971 03:22:19-SEP-1971 20:22
Axis extremes are T=31-MAR-1989 12:00:31-MAR-2006 12:00
=========
Then I found from the mailing archieve that the one variables can be regridded to the
other grid, with a regridding transformation. I tried that
and apparently it worked but upon close inspection I found that during
transfermation the values differs from the original and one value at
the edge was flagged as bad so my guess is this will affect the correlation
computated.This is what I mean: continuing from above
stat j4pranom2
PRECIP[D=3]-J4PRCLM2
X=70E:90E@AV4, Y=6.2N:25N@AV4
X: N/A
Y: N/A
Z: N/A
TIME: 31-MAR-1989 12:00 to 31-MAR-2006 12:00
DATA SET: ./j4pranom2.nc
Total # of data points: 17 (1*1*1*17)
# flagged as bad data: 0
Minimum value:
-1.722
Maximum value: 4.0644
Mean value: 0.00030241 (unweighted average)
Standard deviation: 1.2375
let q=j4pranom2[d=2,gt=p]
stat q
J4PRANOM2[D=j4pranom2,GT=P]
X: N/A
Y: N/A
Z: N/A
TIME: 17-MAR-1989 09:00 to 17-MAR-2006 09:00
DATA SET: N/A
Total # of data points: 17
(1*1*1*17)
# flagged as bad data: 1
Minimum value: -1.6715
Maximum value: 3.8625
Mean value: -0.0095812 (unweighted average)
Standard deviation: 1.2196
============
I look forward to your advice.
Best regards,
Jagadish
=====
Below is the ncdump output of the files:
ncdump -h HCIyear17.nc
netcdf HCIyear17 {
dimensions:
LON = 1 ;
LAT = 1 ;
LEV2_2 = 1 ;
TIME = UNLIMITED ; // (17 currently)
bnds = 2 ;
variables:
double LON(LON) ;
LON:units = "degrees_east"
;
LON:modulo = 360. ;
LON:point_spacing = "even" ;
LON:axis = "X" ;
double LAT(LAT) ;
LAT:units = "degrees_north" ;
LAT:point_spacing = "even" ;
LAT:axis = "Y" ;
double LEV2_2(LEV2_2) ;
LEV2_2:units = "Pa"
;
LEV2_2:point_spacing = "even" ;
LEV2_2:axis = "Z" ;
double TIME(TIME) ;
TIME:units = "days since 1989-01-01 00:00:00" ;
TIME:time_origin = "01-JAN-1989 00:00:00" ;
TIME:axis = "T" ;
TIME:bounds = "TIME_bnds" ;
double TIME_bnds(TIME, bnds) ;
float HCI(TIME,
LEV2_2, LAT, LON) ;
HCI:missing_value = -1.e+34f ;
HCI:_FillValue = -1.e+34f ;
HCI:long_name = "V850ANOM-V200ANOM" ;
HCI:history = "From HCI" ;
// global attributes:
:history = "FERRET V6.5 5-Aug-11" ;
:Conventions = "CF-1.0" ;
ncdump -h
j4pranom2.nc
netcdf j4pranom2 {
dimensions:
TIME = UNLIMITED ; // (17 currently)
bnds = 2 ;
variables:
double TIME(TIME) ;
TIME:units = "hours since 1971-01-01 00:00:00" ;
TIME:time_origin = "01-JAN-1971 00:00:00" ;
TIME:axis = "T" ;
TIME:bounds = "TIME_bnds" ;
double TIME_bnds(TIME, bnds) ;
float J4PRANOM2(TIME) ;
J4PRANOM2:missing_value = -1.e+34f ;
J4PRANOM2:_FillValue = -1.e+34f
;
J4PRANOM2:long_name = "PRECIP[D=3]-J4PRCLM2" ;
J4PRANOM2:long_name_mod = "X=70E:90E@AV4, Y=6.2N:25N@AV4" ;
// global attributes:
:history = "FERRET V6.5 5-Aug-11" ;
:Conventions = "CF-1.0" ;
}