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Re: [ferret_users] regriddidng



Hi Robert,

Your data is on curvilinear grids? It looks like at least the first is.

We have in development a project to make all of this more seamless; and at the same time implement the much-faster code from ESMF (Earth System Modeling Framework).  This work is scheduled to be finished in the next several months.

Meanwhile, you might be able to use one of the SAMPLEXY_CURV functions, picking out points from one grid and populating another.  See

yes? show function samplexy_curv*

There are also a pair of functions for mapping a curvilinear grid to a rectilinear one,

yes? show function curv_to_rect*
CURV_TO_RECT(V,mapping)
    Apply mapping to regrid from curvilinear to rectangular grid
    V: Variable to regrid, on curvilinear grid V(x,y,z,t,e,f)
    mapping: mapping computed by curv_to_rect_MAP

CURV_TO_RECT_MAP(lon_in,lat_in,grid_out,radius)
    Compute mapping for regridding: curvilinear to rectangular grid.
    lon_in: Source grid longitudes (2-D) (degrees)
    lat_in: Source grid latitudes (2-D) (degrees)
    grid_out: Any variable on destination Longitude-Latitude grid, Lon and Lat (degrees)
    radius: Source points falling within radius are included in mapping to destination point (degrees)
and vice versa,
RECT_TO_CURV(V,lon_bounds_out,lat_bounds_out,missing_allowed)
    Regrid from rectangular to curvilinear grid
    V: variable V(x,y,z,t,e,f) on rectilinear grid
    lon_bounds_out: Destination curvilinear grid longitude bounds(2-D) (degrees)
    lat_bounds_out: Destination curvilinear grid latitude bounds(2-D) (degrees)
    missing_allowed: number of missing values allowed in four surrounding source cells: 0 to 3
Best,
Ansley


On 11/10/2015 4:35 PM, Osinski, Robert FORNATL, PL wrote:
Ansley, Paulo,
thank you very much for yours prompt answers but it wasn't exactly what I need. I've studied ferret documentation before I asked my question to the mailing-list but have not found answer.

My problem, in other words, is that I have satellite ice concentration on grid 1280x720 (x=1:1280:1/y=1:720:1) and modeled ice concentration on grid 5120x2880 (x=1:5120:1/y=1:2880:1) (see attached figures).
I want to draw satellite ice concentration on modeled ice. What I know is that every fourth fine resolution grid point is in the same place as coarse grid point. So for instance coarse resolution value of concentration of x=10/y=10 should be at fine resolution grid x=40/y=40, but there is no value for x=39/y=39 (interpolation is needed) and so on,
Thanks in advance,
Robert
 

From: owner-ferret_users@xxxxxxxx [owner-ferret_users@xxxxxxxx] on behalf of Ansley Manke [ansley.b.manke@xxxxxxxx]
Sent: Tuesday, November 10, 2015 9:19 AM
To: ferret_users@xxxxxxxx
Subject: Re: [ferret_users] regriddidng

Hi Robert,
This is a one-line command in Ferret.  You have several options for the regridding transformation; by default it's a linear interpolation.
Perhaps the best thing to point you to is the regridding demo.  From the Ferret command line,

yes? go regridding_demo

The command window has description and comments along with the Ferret commands; and you'll get plots showing what is going on.

If you're a new user, welcome! I'd suggest exploring this page,
http://ferret.pmel.noaa.gov/Ferret/documentation/ferret-tutorials

Ansley

On 11/10/2015 2:56 AM, Osinski, Robert FORNATL, PL wrote:
Dear ferreters,
I need your help in interpolating and drawing two datasets. The first data set is on coarse grid x=1:1280:1/y=1:720:1 and the second on fine one x=1:5120:1/y=1:2880:1. Each 4th grid point in the fine grid is the same as in coarse resolution grid in space so
coarse res. grid point    fine res. grid point 
(1,1)                            (4,4)
(1,2)                            (4,8)
(2,2)                            (8,8)
.....
I need to draw variable which is defined on coarse grid, on fine grid. Obviously there will be "empty" grid points on fine grid so it should be interpolate,
Thanks in advance,
Robert Osinski
NPS,
Monterey, CA



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