[gradsusr] using fwrite

[Alauda arvensis]

Dear GrADS users,

I wish to open a GrADS file (test.ctl) and save one variable to a different
file (out4.ctl).  For this purpose I type the following:


open test.ctl

set fwrite out4.dat

set gxout fwrite
d var130

I now have a binary file called "out4.dat" which contains my variable
"var130". To open it in GrADS I need to create the respective .ctl-file. I
copy it from test.ctl and make a few changes (see both test.ctl and out4.ctl
below). I can open "out4" in GrADS and display "var130". Unfortunately the
data does not display correctly: all longitude values are displayed
correctly but all latitude values are upside down, comparible to the effect
of a mirrow.

My questions:


(1) Why is my data not displaying correctly and what do I need to do to fix
this?

(2) Is it possible to save more than 1 variable in a binary file? I tried
this by applying the steps above and typing after "d var130" also "d
var157". I then apply the respective changes in the .ctl-file (i.e. VARS 2
and var157 14 157,100 var157). However, I can only display "var130" and not
"var157".
(3) Is this methodology (fwrite) the best way to save changes after the
manipulation of a GrADS file?


Thank you very much in advance.



With kind regards,

Chris

###################################
test.ctl


* Generated by CDO version 1.4.0

*

DSET ^test.grb

DTYPE GRIB

INDEX ^test.gmp

XDEF 55 LINEAR 270.000000 1.125000

YDEF 47 LEVELS -40.934 -39.813 -38.691 -37.570 -36.448 -35.327

-34.205 -33.084 -31.962 -30.841 -29.719 -28.598

-27.476 -26.355 -25.234 -24.112 -22.991 -21.869

-20.748 -19.626 -18.505 -17.383 -16.262 -15.140

-14.019 -12.897 -11.776 -10.654 -9.533 -8.411

-7.290 -6.168 -5.047 -3.925 -2.804 -1.682

-0.561 0.561 1.682 2.804 3.925 5.047

6.168 7.290 8.411 9.533 10.654

ZDEF 14 LEVELS 1000 925 850 700 500 400 300 250 200 150

100 70 50 30

TDEF 4 LINEAR 00:00Z01jan1960 1dy

TITLE test.grb T31 grid

OPTIONS yrev

UNDEF -9e+33

VARS 5

var130 14 130,100 var130

var157 14 157,100 var157

var129 14 129,100 var129

var131 14 131,100 var131

var132 14 132,100 var132
ENDVARS

###################################

out4.ctl


* Generated by CDO version 1.4.0

*

DSET ^out4.dat

XDEF 55 LINEAR 270.000000 1.125000

YDEF 47 LEVELS -40.934 -39.813 -38.691 -37.570 -36.448 -35.327

-34.205 -33.084 -31.962 -30.841 -29.719 -28.598

-27.476 -26.355 -25.234 -24.112 -22.991 -21.869

-20.748 -19.626 -18.505 -17.383 -16.262 -15.140

-14.019 -12.897 -11.776 -10.654 -9.533 -8.411

-7.290 -6.168 -5.047 -3.925 -2.804 -1.682

-0.561 0.561 1.682 2.804 3.925 5.047

6.168 7.290 8.411 9.533 10.654

ZDEF 14 LEVELS 1000 925 850 700 500 400 300 250 200 150

100 70 50 30

TDEF 4 LINEAR 00:00Z01jan1960 1dy

TITLE out4.dat

OPTIONS yrev

UNDEF -9e+33

VARS 1

var130 14 130,100 var130

ENDVARS
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