Hi David,
I am just following on a previous posted topic related to Lambert Conformal
Conic grid, I plan to re-project (or regrid) a grid data which has the
following information:
dimensions:
x = 189 ;
y = 227 ;
time = 365 ;
nv = 2 ;
variables:
short lambert_conformal_conic ;
lambert_conformal_conic:grid_mapping_name = "lambert_conformal_conic" ;
lambert_conformal_conic:longitude_of_central_meridian = -100. ;
lambert_conformal_conic:latitude_of_projection_origin = 42.5 ;
lambert_conformal_conic:false_easting = 0. ;
lambert_conformal_conic:false_northing = 0. ;
lambert_conformal_conic:standard_parallel = 25., 60. ;
double x(x) ;
x:units = "m" ;
x:long_name = "x coordinate of projection" ;
x:standard_name = "projection_x_coordinate" ;
double y(y) ;
y:units = "m" ;
y:long_name = "y coordinate of projection" ;
y:standard_name = "projection_y_coordinate" ;
double time(time) ;
time:long_name = "time" ;
time:calendar = "standard" ;
time:units = "days since 1980-01-01 00:00:00 UTC" ;
time:bounds = "time_bnds" ;
double lat(y, x) ;
lat:units = "degrees_north" ;
lat:long_name = "latitude coordinate" ;
lat:standard_name = "latitude" ;
double lon(y, x) ;
lon:units = "degrees_east" ;
lon:long_name = "longitude coordinate" ;
lon:standard_name = "longitude" ;
short yearday(time) ;
yearday:long_name = "yearday" ;
yearday:valid_range = 1s, 365s ;
float prcp(time, y, x) ;
prcp:long_name = "daily total precipitation" ;
prcp:units = "mm/day" ;
prcp:missing_value = -9999.f ;
prcp:_FillValue = -9999.f ;
prcp:valid_range = 0.f, 200.f ;
prcp:coordinates = "lat lon" ;
prcp:grid_mapping = "lambert_conformal_conic" ;
prcp:cell_methods = "area: sum time: sum" ;
double time_bnds(time, nv) ;
I need to do the following:
1) change the projection into lat/lon
2)regrid the data from higher resolution into lower resolution(aggregating)
I am asking which will be the first to do and how can I do
it(lambert_conformal_conic to lon/lat).
Looking forward to hearing from you.
Best Regards
Ping
On Fri, Aug 10, 2012 at 4:00 PM, David Brown <dbrown@ucar.edu> wrote:
> Hi Gualberto,
> I am enclosing a modified version of the script that uses NCL to generate
> the 2D lat/lon coordinate arrays and write them to a file. To demonstrate
> their correctness, it uses them to
> transform the data into an orthographic projection. You can use the
> lat/lon arrays to perform the re-gridding, step 4 of the process outlined
> by Dave Allured. For that I recommend studying the
> ESMF regridding examples at
> http://www.ncl.ucar.edu/Applications/ESMF.shtml. You will need NCL
> 6.1.0-beta if you don't have it already. I also am attaching the
> orthographic plot.
> -dave
>
>
>
>
> On Aug 9, 2012, at 11:41 PM, Gualberto Hernández Juárez wrote:
>
> Dave,
>
> I offer you excuse for late reply,
>
> So I understand with the file you sent me "lcnative.ncl" I can now run the
> regridding?
>
> You will have some very basic example that can serve as reference to do it
> ? I suppose I have to use ESMF.
>
> Thanks,
> Gualberto
>
> ------------------------------
> Subject: Re: FW: I mean regridding the data to a rectiliniear
> lat / lon grid
> From: dbrown@ucar.edu
> Date: Thu, 9 Aug 2012 17:02:01 -0600
> CC: ncl-talk@ucar.edu
> To: betoic@hotmail.com
>
> Hi Gualberto,
> I have figured out what I think are the correct (or at least close enough)
> parameters to get the right results from the PROJ4 tool. I think the main
> issue I was having is that the Lambert Conformal Conic projection has a
> singularity over the equator, because it ceases to be conic and becomes a
> cylinder. At least NCL does not work with a single parallel set to 0.0.
> However, I can make it work using 2 standard parallels very close to each
> other (0.0 and 0.01). The PROJ4 tool does not give up, but the numbers were
> wrong if you do not do something similar. Anyway it would now be
> possible to generate the 2d lat/lon arrays that you will need for
> re-gridding, either just using PROJ4 or by sampling the projected space in
> NCL. I am attaching a plot of temperature that I think shows the map
> boundaries aligning very well with the data. I also include the version of
> the script that created it.
> -dave
>
>
>
> On Aug 8, 2012, at 1:47 PM, Gualberto Hernández Juárez wrote:
>
> I have not done, mainly because ArcGis also limited in NetCDF format
>
> ------------------------------
> From: dbrown@ucar.edu
> Subject: Re: FW: I mean regridding the data to a rectiliniear
> lat / lon grid
> Date: Wed, 8 Aug 2012 12:46:30 -0600
> To: betoic@hotmail.com
>
> One question: Can you find out the projection parameters and/or the corner
> lat/lon values using ArcGIS?
> -dave
>
> On Aug 8, 2012, at 12:35 PM, Gualberto Hernández Juárez wrote:
>
>
> Dave,
>
> This is how I see it in ArcGIS, corresponds to the same variable MSLP. As
> you said the picture you sent me is a little shaky.
>
> Gualberto.
>
>
> ------------------------------
> From: dbrown@ucar.edu
> Subject: Re: FW: I mean regridding the data to a rectiliniear
> lat / lon grid
> Date: Wed, 8 Aug 2012 11:17:02 -0600
> To: betoic@hotmail.com
>
> I was hoping for an image with the continental boundaries correctly
> placed. To show you what I mean here is the best I have been able to do
> using NCL. The trick is to figure out the correct projection parameters and
> the lat/lon locations of the lower left and upper right corner points. I
> did this using the PROJ4 projection tool (similar in capabilities to the
> tool Dave Allured recommended -- MPS Geotrans). But I am not sure I got the
> right values because it looks to me like the data does not quite fit the
> map outlines. I would not trust any re-gridding operation if I could not
> first get the the map outlines correctly placed. It looks to me (based on
> plotting a number of the pressure and temperature time steps) that the
> lower part of Mexico and Central America is skewed to the right and that
> not so much of South America should be visible. Anyway so you know what I
> am talking about I am attaching the plot I came up with in NCL. Also the
> script as it exists now. Perhaps you have access to more information about
> the projection parameters?
> -dave
>
>
>
>
> On Aug 7, 2012, at 8:20 PM, Gualberto Hern�ndez Ju�rez wrote:
>
>
>
> Dave,
>
> I send the image
>
> ------------------------------
> From: dbrown@ucar.edu
> Subject: Re: FW: I mean regridding the data to a rectiliniear
> lat / lon grid
> Date: Tue, 7 Aug 2012 18:16:24 -0600
> To: betoic@hotmail.com
>
> Sorry maybe I misunderstand. I have the NetCDF file MMOUT_DOMAIN1.nc. But
> I thought you said you uploaded an image (picture ??) of the plot you made
> in ArcMap. I would like to see the picture if you can send it.
> -dave
>
> On Aug 7, 2012, at 5:23 PM, Gualberto Hern�ndez Ju�rez wrote:
>
> This is the file MMOUT_DOMAIN1.nc
>
> The file you put in place it ftp://ftp.cgd.ucar.edu/incoming/
>
>
> ------------------------------
> From: dbrown@ucar.edu
> Subject: Re: FW: I mean regridding the data to a rectiliniear
> lat / lon grid
> Date: Tue, 7 Aug 2012 17:19:16 -0600
> To: betoic@hotmail.com
>
> (offline)
> I need to know what you called the file in order to retrieve it.
> -dave
>
> On Aug 7, 2012, at 5:10 PM, Gualberto Hern�ndez Ju�rez wrote:
>
> Thanks for your reply Dave,
>
> I plot the file only in ArcMap of ArcGIS, place an image in the directory:
>
>
> ftp://ftp.cgd.ucar.edu/incoming/
>
>
> I just have to put the map of the Mexican republic.
>
>
> ------------------------------
> Subject: Re: FW: I mean regridding the data to a rectiliniear
> lat / lon grid
> From: dbrown@ucar.edu
> Date: Tue, 7 Aug 2012 16:41:41 -0600
> CC: ncl-talk@ucar.edu
> To: betoic@hotmail.com
>
> Hi Gaulberto,
> Here is a way to write the text file as X/Y pairs as Dave Allured
> suggested:
>
> f = addfile ("MMOUT_DOMAIN1.nc", "r")
> x = f->lon
> y = f->lat
> nx = dimsizes(x)
> ny = dimsizes(y)
> x2d = conform_dims((/ny,nx/),x,1)
> y2d = conform_dims((/ny,nx/),y,0)
> outstr = sprintf("%9.3f",x2d) + " " + sprintf("%9.3f",y2d)
> asciiwrite("xy.txt",outstr)
>
> I wonder if you have a plot of this grid in its native (Lambert Conformal)
> configuration. I have tried to plot it based on the LC parameters given in
> the data file, but so far I have been unsuccessful.
> A correct plot of the domain would help.
>
> If you can get NCL to plot the data correctly in its native projection,
> then it is possible to compute the lat/lon coordinates using NCL by itself.
> -dave
>
>
> On Aug 7, 2012, at 2:06 PM, Gualberto Hern�ndez Ju�rez wrote:
>
> Dave,
> How to make the text file, which you mention in the first point.
>
> Thanks
> Gualberto
>
> > Date: Tue, 7 Aug 2012 11:44:09 -0600
> > Subject: Re: I mean regridding the data to a rectiliniear lat
> / lon grid
> > From: dave.allured@noaa.gov
> > To: betoic@hotmail.com
> > CC: ncl-talk@ucar.edu
> >
> > Here is one way. I am sure there are others.
> >
> > 1. Use NCL to make a text file containing a 1-dimensional ordered
> > list of all X/Y coordinate pairs.
> >
> > 2. Use MPS Geotrans in batch mode to translate the list of
> > coordinates from Lambert Conformal to terrestrial lat/lon. It's free
> > software, and it supports a huge variety of known terrestrial
> > coordinate systems.
> >
> > http://earth-info.nga.mil/GandG/geotrans/
> >
> > 3. Use NCL to read in the translated coordinates, and reshape them
> > into 2-D lat and lon coordinate arrays.
> >
> > 4. Use one of the many NCL regridding functions, plus the 2-D
> > coordinates from step 3, to regrid the data array to a rectilinear
> > grid of your choice.
> >
> > This is an overview. Steps 1 and 3 are fairly straightforward NCL
> > coding. Steps 2 and 4 will involve significant study to get them
> > working correctly. HTH.
> >
> > --Dave
> >
> > On Tue, Aug 7, 2012 at 10:54 AM, Gualberto Hern�ndez Ju�rez
> > <betoic@hotmail.com> wrote:
> > > I need *regrid* the 2D lat/lon to a rectilinear lat lon.
> > >
> > > any comments will be grateful enough support, I'm new to NCL.
> > >
> > > Thank you,
> > > Gualberto
> > >
> > >
> > >> Date: Tue, 7 Aug 2012 10:41:42 -0600
> > >> From: shea@ucar.edu
> > >> To: betoic@hotmail.com
> > >> CC: ncl-talk@ucar.edu
> > >> Subject: Re: I mean regridding the data to a rectiliniear
> lat /
> > >> lon grid
> > >>
> > >> Technically, this is already a rectilinear grid.
> > >>
> > >> double lat ( lat )
> > >> _CoordinateAxisType : GeoY
> > >> axis : Y
> > >> grid_spacing : 27.0 km
> > >> long_name : y coordinate of projection
> > >> standard_name : projection_y_coordinate
> > >> units : km
> > >>
> > >> double lon ( lon )
> > >> _CoordinateAxisType : GeoX
> > >> axis : X
> > >> grid_spacing : 27.0 km
> > >> long_name : x coordinate of projection
> > >> standard_name : projection_x_coordinate
> > >> units : km
> > >>
> > >> float u10 ( time, lat, lon )
> > >> long_name : 10 m u wind (m/sec)
> > >> _FillValue : -9999
> > >> grid_mapping : Lambert_Conformal
> > >>
> > >> The issue is that the poorly named 'lat' and 'lon' variables
> > >> should be (say) 'y' and 'x'.
> > >>
> > >> Basically, the projection information
> > >>
> > >> character Lambert_Conformal ( ncl_scalar )
> > >> grid_mapping_name : lambert_conformal_conic
> > >> long_name :
> > >> latitude_of_projection_origin : 0
> > >> longitude_of_central_meridian : -124.17
> > >> false_easting : 0
> > >> false_northing : -27
> > >> standard_parallel : 0
> > >> _CoordinateTransformType : Projection
> > >> _CoordinateAxisTypes : GeoX GeoY
> > >> earth_shape : Earth spherical with radius of 6,371,229.0 m
> > >> earth_radius : 6371229
> > >>
> > >> must be used to generate two-dimensional latitude and longitude
> > >> coordinates for each grid point. Then the data can be plotted on the
> > >> lambert map projection. Is this what you want?
> > >>
> > >> *** I have no idea how to do this. Maybe someone else does. ***
> > >>
> > >> Then, if you really want to *regrid* the 2D lat/lon to a rectilinear
> > >> lat lon, you would have to use the ESMF regridding
> > >> http://www.ncl.ucar.edu/Applications/ESMF.shtml
> > >>
> > >>
> > >> On 8/7/12 10:12 AM, Gualberto Hern�ndez Ju�rez wrote:
> > >> > Hi,
> > >> >
> > >> > I mean regridding the data to a rectiliniear lat / lon grid
> > >> >
> > >> > locate the file in the directory:
> > >> >
> > >> > ftp://ftp.cgd.ucar.edu/incoming/
> > >> >
> > >> > or you can download from this link:
> > >> >
> > >> > https://dl.dropbox.com/u/96409134/MMOUT_DOMAIN1.nc
> > >> >
> > >> > Thanks I'll be awaiting your response.
> > >> > Gualberto
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> Ping Yang, Ph.D.
> CUNY Environmental Crossroads Initiative
> Marshak Science Building - Suite 925
> The City College of New York - CUNY
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Received on Thu Oct 18 21:49:16 2012
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