Rotated lon-lat grid
Added by praveen rai over 5 years ago
Hello all,
I have a Model output for which the coordinates are in rotated lon/lat format. I want to convert it to the regular lon/lat but I don't know how to change the rotated values to exact regular lon/lat value i.e. starting x and y values in regular coordinates. Once I have the regular regrid file, I think I can use setgrid command on my files. I want to regrid my data similar to my area of interest.
I am attaching the rotated regrid file here along with the figure showing the area of interest (this figure is generated using Panoply which automatically convert rotated values to lon/lat). I would also like to mask my data only over the land region, and any help related to all these queries will be highly appreciated.
Thanks
Praveen
| FIB_in_regrid_CAS-44_oro.png (153 KB) FIB_in_regrid_CAS-44_oro.png | |||
| regrid (469 Bytes) regrid | |||
| timmean_e031001m200002.nc (12.4 MB) timmean_e031001m200002.nc |
Replies (22)
RE: Rotated lon-lat grid - Added by Karin Meier-Fleischer over 5 years ago
Hi Praveen,
you can use the remap operators to remap the data of the curvilinear grid to lonlat grid. See https://code.mpimet.mpg.de/projects/cdo/embedded/cdo.pdf
For example, remap the data to global 1x1 degree rectilinear lonlat grid:
cdo -f nc -remapbil,r360x180 timmean_e031001m200002.nc ooo.nc
About masking see https://code.mpimet.mpg.de/projects/cdo/wiki/FAQ#How-can-I-create-a-1x1-degree-landsea-mask
How to mask a sub-region see maskregion operator https://code.mpimet.mpg.de/projects/cdo/embedded/cdo.pdf#subsection.2.6.11
-Karin
RE: Rotated lon-lat grid - Added by praveen rai over 5 years ago
Thanks for the reply Karin. The resolution of my data is 0.44 degree. And the remapbil will convert it to a global grid with 1 degree resolution. I am more interested in remapping it to the similar x and y values as in my data with 0.44 degree resolution. I hope it's possible.
RE: Rotated lon-lat grid - Added by Karin Meier-Fleischer over 5 years ago
You have to define it as you want, e.g. ~0.44 degrees
cdo remapbil,r818x409 timmean_e031001m200002.nc outfile.nc
cdo sinfon outfile.nc
File format : NetCDF2
-1 : Institut Source T Steptype Levels Num Points Num Dtype : Parameter name
1 : MPIMET REMO v instant 1 1 334562 1 F32 : QDB
2 : MPIMET REMO v instant 1 1 334562 1 F32 : QDBL
3 : MPIMET REMO v instant 1 1 334562 1 F32 : QDBW
4 : MPIMET REMO v instant 1 1 334562 1 F32 : QDBI
5 : MPIMET REMO v instant 1 1 334562 1 F32 : PS
6 : MPIMET REMO v instant 1 1 334562 1 F32 : TS
7 : MPIMET REMO v instant 1 1 334562 1 F32 : TSL
8 : MPIMET REMO v instant 1 1 334562 1 F32 : TSW
9 : MPIMET REMO v instant 1 1 334562 1 F32 : TSI
10 : MPIMET REMO v instant 1 1 334562 1 F32 : WS
11 : MPIMET REMO v instant 1 1 334562 1 F32 : SN
12 : MPIMET REMO v instant 1 1 334562 1 F32 : APRL
13 : MPIMET REMO v instant 1 1 334562 1 F32 : APRC
14 : MPIMET REMO v instant 1 1 334562 1 F32 : APRS
15 : MPIMET REMO v instant 1 1 334562 1 F32 : VDIS
16 : MPIMET REMO v instant 1 1 334562 1 F32 : AHFS
17 : MPIMET REMO v instant 1 1 334562 1 F32 : AHFL
18 : MPIMET REMO v instant 1 1 334562 1 F32 : PSRED
19 : MPIMET REMO v instant 1 1 334562 1 F32 : USTAR3
20 : MPIMET REMO v instant 1 1 334562 1 F32 : RUNOFF
21 : MPIMET REMO v instant 1 1 334562 1 F32 : DRAIN
22 : MPIMET REMO v instant 1 1 334562 1 F32 : ACLCV
23 : MPIMET REMO v instant 1 1 334562 1 F32 : ACLCOV
24 : MPIMET REMO v instant 1 2 334562 1 F32 : U10
25 : MPIMET REMO v instant 1 2 334562 1 F32 : V10
26 : MPIMET REMO v instant 1 3 334562 1 F32 : TEMP2
27 : MPIMET REMO v instant 1 3 334562 1 F32 : DEW2
28 : MPIMET REMO v instant 1 1 334562 1 F32 : TSURF
29 : MPIMET REMO v instant 1 1 334562 1 F32 : TD
30 : MPIMET REMO v instant 1 2 334562 1 F32 : WIND10
31 : MPIMET REMO v instant 1 1 334562 1 F32 : AZ0
32 : MPIMET REMO v instant 1 1 334562 1 F32 : AZ0L
33 : MPIMET REMO v instant 1 1 334562 1 F32 : AZ0W
34 : MPIMET REMO v instant 1 1 334562 1 F32 : AZ0I
35 : MPIMET REMO v instant 1 1 334562 1 F32 : ALB
36 : MPIMET REMO v instant 1 1 334562 1 F32 : ALBEDO
37 : MPIMET REMO v instant 1 1 334562 1 F32 : ALSOL
38 : MPIMET REMO v instant 1 1 334562 1 F32 : ALSOW
39 : MPIMET REMO v instant 1 1 334562 1 F32 : ALSOI
40 : MPIMET REMO v instant 1 1 334562 1 F32 : SRADS
41 : MPIMET REMO v instant 1 1 334562 1 F32 : TRADS
42 : MPIMET REMO v instant 1 4 334562 1 F32 : SRAD0
43 : MPIMET REMO v instant 1 4 334562 1 F32 : TRAD0
44 : MPIMET REMO v instant 1 1 334562 1 F32 : USTR
45 : MPIMET REMO v instant 1 1 334562 1 F32 : USTRL
46 : MPIMET REMO v instant 1 1 334562 1 F32 : USTRW
47 : MPIMET REMO v instant 1 1 334562 1 F32 : USTRI
48 : MPIMET REMO v instant 1 1 334562 1 F32 : VSTR
49 : MPIMET REMO v instant 1 1 334562 1 F32 : VSTRL
50 : MPIMET REMO v instant 1 1 334562 1 F32 : VSTRW
51 : MPIMET REMO v instant 1 1 334562 1 F32 : VSTRI
52 : MPIMET REMO v instant 1 1 334562 1 F32 : EVAP
53 : MPIMET REMO v instant 1 1 334562 1 F32 : EVAPL
54 : MPIMET REMO v instant 1 1 334562 1 F32 : EVAPW
55 : MPIMET REMO v instant 1 1 334562 1 F32 : EVAPI
56 : MPIMET REMO v instant 1 1 334562 1 F32 : TDCL
57 : MPIMET REMO v instant 1 1 334562 1 F32 : TRAFS
58 : MPIMET REMO v instant 1 4 334562 1 F32 : TRAF0
59 : MPIMET REMO v instant 1 1 334562 1 F32 : TCLFS
60 : MPIMET REMO v instant 1 4 334562 1 F32 : TCLF0
61 : MPIMET REMO v instant 1 1 334562 1 F32 : WL
62 : MPIMET REMO v instant 1 1 334562 1 F32 : VGRAT
63 : MPIMET REMO v instant 1 1 334562 1 F32 : VLT
64 : MPIMET REMO v instant 1 3 334562 1 F32 : T2MAX
65 : MPIMET REMO v instant 1 3 334562 1 F32 : T2MIN
66 : MPIMET REMO v instant 1 4 334562 1 F32 : SRAD0U
67 : MPIMET REMO v instant 1 1 334562 1 F32 : SRADSU
68 : MPIMET REMO v instant 1 1 334562 1 F32 : TRADSU
69 : MPIMET REMO v instant 1 1 334562 1 F32 : TSN
70 : MPIMET REMO v instant 1 1 334562 1 F32 : TD3
71 : MPIMET REMO v instant 1 1 334562 1 F32 : TD4
72 : MPIMET REMO v instant 1 1 334562 1 F32 : TD5
73 : MPIMET REMO v instant 1 1 334562 1 F32 : SEAICE
74 : MPIMET REMO v instant 1 1 334562 1 F32 : SICED
75 : MPIMET REMO v instant 1 1 334562 1 F32 : TEFF
76 : MPIMET REMO v instant 1 1 334562 1 F32 : TSMAX
77 : MPIMET REMO v instant 1 1 334562 1 F32 : TSMIN
78 : MPIMET REMO v instant 1 2 334562 1 F32 : WIMAX
79 : MPIMET REMO v instant 1 1 334562 1 F32 : TOPMAX
80 : MPIMET REMO v instant 1 1 334562 1 F32 : SNMEL
81 : MPIMET REMO v instant 1 1 334562 1 F32 : TSLIN
82 : MPIMET REMO v instant 1 1 334562 1 F32 : AHFICE
83 : MPIMET REMO v instant 1 1 334562 1 F32 : QRES
84 : MPIMET REMO v instant 1 1 334562 1 F32 : DSNAC
85 : MPIMET REMO v instant 1 1 334562 1 F32 : QVI
86 : MPIMET REMO v instant 1 1 334562 1 F32 : ALWCVI
87 : MPIMET REMO v instant 1 1 334562 1 F32 : var456
88 : MPIMET REMO v instant 1 1 334562 1 F32 : BFLHSL
89 : MPIMET REMO v instant 1 1 334562 1 F32 : BFLHSW
90 : MPIMET REMO v instant 1 1 334562 1 F32 : BFLHSI
91 : MPIMET REMO v instant 1 1 334562 1 F32 : var457
92 : MPIMET REMO v instant 1 1 334562 1 F32 : BFLQDSL
93 : MPIMET REMO v instant 1 1 334562 1 F32 : BFLQDSW
94 : MPIMET REMO v instant 1 1 334562 1 F32 : BFLQDSI
95 : MPIMET REMO v instant 1 1 334562 1 F32 : QDBOXS
96 : MPIMET REMO v instant 1 1 334562 1 F32 : QWBOXS
97 : MPIMET REMO v instant 1 1 334562 1 F32 : EKBOXS
98 : MPIMET REMO v instant 1 1 334562 1 F32 : FHBOXS
99 : MPIMET REMO v instant 1 1 334562 1 F32 : FIBOXS
100 : MPIMET REMO v instant 1 1 334562 1 F32 : TLAMBDA
101 : MPIMET REMO v instant 1 1 334562 1 F32 : DLAMBDA
102 : MPIMET REMO v instant 1 1 334562 1 F32 : PORVOL
103 : MPIMET REMO v instant 1 1 334562 1 F32 : WI3
104 : MPIMET REMO v instant 1 1 334562 1 F32 : WI4
105 : MPIMET REMO v instant 1 1 334562 1 F32 : WI5
106 : MPIMET REMO v instant 1 1 334562 1 F32 : WI
107 : MPIMET REMO v instant 1 1 334562 1 F32 : WICL
108 : MPIMET REMO v instant 1 2 334562 1 F32 : var265
109 : MPIMET REMO v instant 1 2 334562 1 F32 : var266
110 : MPIMET REMO v instant 1 2 334562 1 F32 : var275
111 : MPIMET REMO v instant 1 1 334562 1 F32 : var271
112 : MPIMET REMO v instant 1 1 334562 1 F32 : var276
113 : MPIMET REMO v instant 1 1 334562 1 F32 : var1
114 : MPIMET REMO v instant 1 1 334562 1 F32 : var2
115 : MPIMET REMO v instant 1 1 334562 1 F32 : var3
116 : MPIMET REMO v instant 1 1 334562 1 F32 : var4
117 : MPIMET REMO v instant 1 1 334562 1 F32 : var5
118 : MPIMET REMO v instant 1 1 334562 1 F32 : var12
119 : MPIMET REMO v instant 1 1 334562 1 F32 : var13
120 : MPIMET REMO v instant 1 1 334562 1 F32 : var301
121 : MPIMET REMO v instant 1 1 334562 1 F32 : var302
122 : MPIMET REMO v instant 1 1 334562 1 F32 : var303
123 : MPIMET REMO v instant 1 1 334562 1 F32 : var336
124 : MPIMET REMO v instant 1 1 334562 1 F32 : var287
125 : MPIMET REMO v instant 1 1 334562 1 F32 : var288
Grid coordinates :
1 : lonlat : points=334562 (818x409)
lon : 0 to 359.5599 by 0.4400978 degrees_east circular
lat : -90 to 90 by 0.4411765 degrees_north
Vertical coordinates :
1 : surface : levels=1
2 : height : levels=1
height : 10 m
3 : height : levels=1
height_2 : 2 m
4 : hybrid : levels=1
lev : 1 level
available : vct
Time coordinate : 1 step
YYYY-MM-DD hh:mm:ss YYYY-MM-DD hh:mm:ss YYYY-MM-DD hh:mm:ss YYYY-MM-DD hh:mm:ss
2000-02-00 00:00:00
RE: Rotated lon-lat grid - Added by praveen rai over 5 years ago
Thanks Karin. I have managed to convert rotated lon/lat. Now after doing the the cdo griddes I am getting something like,
53.33745 53.06757 52.79612 52.52316 52.24871 51.97282 51.69551 51.41683
51.13681 50.85549 50.57288 50.28905 50.00401 49.71778 49.43042 49.14193
48.85236 48.56172 48.27007 47.9774 47.68375 47.38915 47.09362 46.7972
46.49989 46.20173 45.90274 45.60295 45.30236 45.00103 44.69894
gridtype = projection
gridsize = 25929
xsize = 201
ysize = 129
xname = x
xlongname = "index_of_lon"
yname = y
ylongname = "index_of_lat"
xfirst = 0
xinc = 1
yfirst = 0
yinc = 1
grid_mapping = Projection
cdo sinfo timmean_FIB_CAS-44_frac.nc
File format : NetCDF
-1 : Institut Source T Steptype Levels Num Points Num Dtype : Parameter ID
1 : unknown unknown v instant 1 1 25929 1 F32 : -1
Grid coordinates :
1 : curvilinear : points=25929 (201x129)
lon : 7.678206 to 147.9288 degrees_east
lat : -0.9850898 to 65.10996 degrees_north
mapping : undefined
x : 0 to 200 by 1
y : 0 to 128 by 1
Vertical coordinates :
1 : surface : levels=1
Time coordinate : 1 step
YYYY-MM-DD hh:mm:ss YYYY-MM-DD hh:mm:ss YYYY-MM-DD hh:mm:ss YYYY-MM-DD hh:mm:ss
0000-00-00 00:00:00
I think it has lon and lat as a normal variable now not as a coordinate variables. Is there any way i can now convert it to coordinate variables??
Thanks for your help.
Praveen
RE: Rotated lon-lat grid - Added by Karin Meier-Fleischer over 5 years ago
The lon and lat variables are 2D-variables and are used as dimension/coordinate variables via the coordinates attribute ascociatted to the data variables.
RE: Rotated lon-lat grid - Added by Cat Fitz about 5 years ago
Dear Karin,
I also tried your suggestion of: cdo remapbil,r360x180 filein.nc fileout.nc
This created the grid as expected, but this is not exactly what I need.
My file is a European Cordex file (cdo sinfo below). I am using the data within the files to create a new .nc file for ingestion to another program, which requires a vector of Lat and a vector of Lon (regular). Is is possible to convert the rlat and rlon to regular lat lon coordinates, so I end up with a Lon vector of 106 length and a Lat vector of 103 length (as opposed to a grid)?
File format : NetCDF4 classic
-1 : Institut Source T Steptype Levels Num Points Num Dtype : Parameter ID
1 : unknown unknown v instant 1 1 10918 1 F32 : -1
Grid coordinates :
1 : curvilinear : points=10918 (106x103)
lon : -44.13997 to 64.41475 degrees_east
lat : 22.20309 to 72.42257 degrees_north
mapping : rotated_latitude_longitude
rlon : -28.21 to 17.99 by 0.44 degrees
rlat : -23.21 to 21.67 by 0.44 degrees
Vertical coordinates :
1 : surface : levels=1
Time coordinate : 60 steps
RefTime = 1949-12-01 00:00:00 Units = days Calendar = standard Bounds = true
YYYY-MM-DD hh:mm:ss YYYY-MM-DD hh:mm:ss YYYY-MM-DD hh:mm:ss YYYY-MM-DD hh:mm:ss
2006-01-16 12:00:00 2006-02-15 00:00:00 2006-03-16 12:00:00 2006-04-16 00:00:00
2006-05-16 12:00:00 2006-06-16 00:00:00 2006-07-16 12:00:00 2006-08-16 12:00:00
2006-09-16 00:00:00 2006-10-16 12:00:00 2006-11-16 00:00:00 2006-12-16 12:00:00
2007-01-16 12:00:00 2007-02-15 00:00:00 2007-03-16 12:00:00 2007-04-16 00:00:00
2007-05-16 12:00:00 2007-06-16 00:00:00 2007-07-16 12:00:00 2007-08-16 12:00:00
2007-09-16 00:00:00 2007-10-16 12:00:00 2007-11-16 00:00:00 2007-12-16 12:00:00
2008-01-16 12:00:00 2008-02-15 12:00:00 2008-03-16 12:00:00 2008-04-16 00:00:00
2008-05-16 12:00:00 2008-06-16 00:00:00 2008-07-16 12:00:00 2008-08-16 12:00:00
2008-09-16 00:00:00 2008-10-16 12:00:00 2008-11-16 00:00:00 2008-12-16 12:00:00
2009-01-16 12:00:00 2009-02-15 00:00:00 2009-03-16 12:00:00 2009-04-16 00:00:00
2009-05-16 12:00:00 2009-06-16 00:00:00 2009-07-16 12:00:00 2009-08-16 12:00:00
2009-09-16 00:00:00 2009-10-16 12:00:00 2009-11-16 00:00:00 2009-12-16 12:00:00
2010-01-16 12:00:00 2010-02-15 00:00:00 2010-03-16 12:00:00 2010-04-16 00:00:00
2010-05-16 12:00:00 2010-06-16 00:00:00 2010-07-16 12:00:00 2010-08-16 12:00:00
2010-09-16 00:00:00 2010-10-16 12:00:00 2010-11-16 00:00:00 2010-12-16 12:00:00Any advice would be appreciated.
RE: Rotated lon-lat grid - Added by Ralf Mueller about 5 years ago
hi Cat!
remapbil does exactly what you discribed - sorry, I don't understand what's missing
cheers
ralf
RE: Rotated lon-lat grid - Added by praveen rai about 5 years ago
Hi Catriona,
Apart from CDO, you can take a look at this ncl script which exactly does what you are trying to do, and maybe after generating one regular lon-lat file, you can use remapbil. I hope it helps.
https://www.dkrz.de/up/news-and-events/workshops-and-trainings/ncl-workshops/rotated-grid
Greetings,
Praveen
RE: Rotated lon-lat grid - Added by Cat Fitz about 5 years ago
Hi Ralf,
Thanks for the quick response. Apologies, I should have been more clear. The command currently provide 'Lon' as 360 long and 'Lat' as 180 long. Is it possible to just extract the lat/lon coordinates for the Cordex area of interest with this command?..so I end up with 'Lon' as 106 long and 'Lat' as 103 long (representing only the European region)? i.e. Can that data be subsequently 'pulled' from the 'Lon' of 360 length and the 'Lat' of 180 length provided by the remapbil command?
I understand that remapbil provides the coordinates for the entire globe, so it is not a case of specifying the size of the original dataset with: cdo remapbil,r106x103 filein.nc fileout.nc
Best wishes.
RE: Rotated lon-lat grid - Added by Cat Fitz about 5 years ago
Thanks for the suggestion Praveen,
I'm going to take a look at it now.
Best wishes.
RE: Rotated lon-lat grid - Added by Cat Fitz about 5 years ago
@Praveen, did you get that ncl script to work for you before?
RE: Rotated lon-lat grid - Added by Ralf Mueller about 5 years ago
Catriona Duffy wrote:
Hi Ralf,
Thanks for the quick response. Apologies, I should have been more clear. The command currently provide 'Lon' as 360 long and 'Lat' as 180 long. Is it possible to just extract the lat/lon coordinates for the Cordex area of interest with this command?..so I end up with 'Lon' as 106 long and 'Lat' as 103 long (representing only the European region)? i.e. Can that data be subsequently 'pulled' from the 'Lon' of 360 length and the 'Lat' of 180 length provided by the
remapbilcommand?
check the operator sellonlatbox
I understand that
remapbilprovides the coordinates for the entire globe, so it is not a case of specifying the size of the original dataset with:cdo remapbil,r106x103 filein.nc fileout.nc
remapbil like all other interpolation operators take the target grid as a parameter. It doesn't matter, if the grid is global or regional. There are 3 ways to describe a grid
- a built-in shortcut like: global_1, r360x180 or others mentioned on the official documentation (chapter 1.3)
- a text representation formated in a way like the output of
cdo griddes <ifile>
For a regular grid this would be just a couple of linescdo griddes -sellonlatbox,20,40,-20,40 -topo,global_2 # # gridID 1 # gridtype = lonlat gridsize = 300 xsize = 10 ysize = 30 xname = lon xlongname = "longitude" xunits = "degrees_east" yname = lat ylongname = "latitude" yunits = "degrees_north" xfirst = 21 xinc = 2 yfirst = -19 yinc = 2
- a datafile that used the target grid - CDO will read the grid from it and use it
In you case (Europe only), you might use this eastlimit=-10.8; southlimit=35.7; eastlimit=69.4; northlimit=72.3
- create the target grid with (set the resolution with the parameter of
topo)cdo -sellonlatbox,-11,70,35,75 -topo,global_2 targetEuropeGrid.nc
- perform the remapping on the original data with the method you need
cdo -remapbil,targetEuropeGrid.nc cordex_input.nc europe_output.nc
hth
ralf
RE: Rotated lon-lat grid - Added by Ralf Mueller about 5 years ago
direct link to the docu i referred to https://code.mpimet.mpg.de/projects/cdo/embedded/index.html#x1-130001.3
RE: Rotated lon-lat grid - Added by Cat Fitz about 5 years ago
Thanks for your help Ralf.
I used your command line and topo wasn't recognised for some reason:
@cdo -sellonlatbox,-11,70,35,75 -topo,global_2 EuropeGrid.nc
cdo(1) topo: Process started
ECCODES ERROR : concept: no match for shortName=topo
ECCODES ERROR : concept: input handle edition=1
!!! grib_set_string( grib_handle* h, "shortName", "topo") !!!
Warning (gribapiDefParam): grib_api: No match for shortName=topo@
I can see that 'topo' is supposed to create a half degree regular grid. When I type cdo --operators, it shows up in the list.
Best wishes.
RE: Rotated lon-lat grid - Added by Karin Meier-Fleischer about 5 years ago
Hi Catriona,
which version are you using? Current version is 1.9.9
cdo -V
RE: Rotated lon-lat grid - Added by Ralf Mueller about 5 years ago
try adding the option '-f nc' right after 'cdo'
RE: Rotated lon-lat grid - Added by Cat Fitz about 5 years ago
Karin, I am using version 1.9.9 (cdo -V returned)Climate Data Operators version 1.9.9rc1 (https://mpimet.mpg.de/cdo)
Ralf Adding the '-f nc' worked a treat. One final question if you don't mind?
I identified the max and min lat and lon from the regular Lat Lon grids in my Cordex file and used them to set the outer bounds of the latlon box selected. I also used 'Global_1 to increase the resolution:cdo -f nc -sellonlatbox,-45,65,22,73 -topo,global_1 test.nc
Then I used as you suggested, the following:cdo -remapbil,test.nc myinputfile.nc europe_output.nc
Is there another option rather than '-topo,global_1' to specify the number of Lon and Lat cells in the grid while simultaneously keeping the latlon box specified? I see from the documentation link you sent that it is possible to use the grid description from another datafile ('1.3.2.2. Grids from data files') or alternatively, can I simply specify the 'xsize*ysize' of the curvilinear grid (which refers to 'ncell' in '1.3.2.4. CDO grids')? I tried:
cdo -f nc -sellonlatbox,-45,65,22,73 -topo,r106x103 test.nc but this is referring to degrees as opposed to the number of cells/gridbox length.
Many thanks for your advice.
RE: Rotated lon-lat grid - Added by Ralf Mueller about 5 years ago
Catriona Duffy wrote:
Is there another option rather than '-topo,global_1' to specify the number of Lon and Lat cells in the grid while simultaneously keeping the latlon box specified? I see from the documentation link you sent that it is possible to use the grid description from another datafile ('1.3.2.2. Grids from data files') or alternatively, can I simply specify the 'xsize*ysize' of the curvilinear grid (which refers to 'ncell' in '1.3.2.4. CDO grids')? I tried:
cdo -f nc -sellonlatbox,-45,65,22,73 -topo,r106x103 test.ncbut this is referring to degrees as opposed to the number of cells/gridbox length.
-topo is a global topography field. so the parameter of topo set the global resolution.
If you have a data file that already has the target grid you are looking for, you can use is for remapping your input data:
cdo -remapbil,dataOnTargetGrid.nc <ifile> <ofile>
you can also setup the target grid as a textfile like I showed before
gridtype = lonlat gridsize = 80000 xsize = 200 ysize = 400 xname = lon xlongname = "longitude" xunits = "degrees_east" yname = lat ylongname = "latitude" yunits = "degrees_north" xfirst = -45 xinc = 0.05 yfirst = 22 yinc = 0.001
you have to adopt the yinc and xinc to set the corners of the area correctly.
Many thanks for your advice.
RE: Rotated lon-lat grid - Added by Cat Fitz almost 5 years ago
Hi Ralf,
If you have a data file that already has the target grid you are looking for, you can use is for remapping your input data:
I don't want to copy the grid exactly, as it is in rotated Lat Lon, but the nc file also has the regular grid on it.
you can also setup the target grid as a textfile like I showed before
I have a textfile called:gridtest.txt in which I have included the following information:
gridtype = lonlat
xsize = 106
ysize = 103
xfirst = -44.75
xinc = 0.5
yfirst = 21.75
yinc = 0.5
I then used this command:cdo griddes -sellonlatbox,-45,65,21.5,73.5 -topo,gridtest.txt
I tweaked the Lat Lons specified in the above command, as the grid being output wasn't 106x103 like I wanted, but rather 106x102 when I used the exact Maximum and Minimum Lat and Lon from the regular grid in the original .nc file. This command created the grid, but now I'm not entirely sure how to use it? I think I need to apply it to an nc file (i.e. test.nc), which I can then use in this command: cdo -remapbil,test.nc myinputfile.nc europe_output.nc Or, can I refer to the grid in another way (i.e. not assign it to 'test.nc', but rather just use the name of the grid directly?)
Perhaps I'm missing something obvious here? Apologies, as I'm new to cdos.
Many thanks.
RE: Rotated lon-lat grid - Added by Cat Fitz almost 5 years ago
I tried adding the 'test.nc' at the end:cdo -f nc -sellonlatbox,-45,65,21.5,73.5 -topo,gridtest.txt test.nc
and then:
cdo -remapbil,test.nc input.nc europe_output.nc
But in Panoply, the Longitude only ranges from -44.75 to 7.75 (Image won't attach for some reason). The latitudes were correct.
RE: Rotated lon-lat grid - Added by Ralf Mueller almost 5 years ago
hi Cat!
Instead of using test.nc you can also use the gridtest.txt as a parameter for remapbil.
created with
cdo -f nc topo,grid t.ncwhere grid is a text file with the content from above. does this look ok for your with respect to the region it covers?
| topo_in_t.png (115 KB) topo_in_t.png |
RE: Rotated lon-lat grid - Added by Ralf Mueller almost 5 years ago
for showing an uploaded image, you need to mention it with exclamation marks around like
!image.png!