Re: [ferret_users] 2D irregular lat and lon in netcdf

[Ansley Manke <ansley.b.manke@xxxxxxxx>]

Hi Ramesh,
Ferret can create graphics using this kind of grid, which we call 
curvilinear data in the documentation. You can make a shad plot of 
variables rain or evap with the command

 shade rain[L=1], nav_lon, nav_lat

 fill evap[L=20], nav_lon, nav_lat

There are also functions to regrid data from a curvilinear grid to a 
rectilinear grid: CURV_TO_RECT_MAP and CURV_TO_RECT.  These functions 
allow you to do analysis or comparisons with data on a retilinear grid.

Ansley

K V Ramesh wrote:

> Dear Ferret users,
>
>          I have model output in netcdf format of dimension (192 x 145) 
> with default axis of xpts and ypts.  The latitude and longitude values 
> stored like variables,  and are in  two dimensional . Is it posible to 
> define grid in 2-D or any other way we can make the netcedf  with 
> default axis in X and  Y using ferret
>
> ncdump -h  histday_may01_jul91.nc  results as follows:
> netcdf histday_may01_jul91 {
> dimensions:
>         x = 192 ;
>         y = 145 ;
>         presnivs = 19 ;
>         time_counter = UNLIMITED ; // (30 currently)
> variables:
>         float nav_lon(y, x) ;
>                 nav_lon:units = "degrees_east" ;
>                 nav_lon:valid_min = -178.0906f ;
>                 nav_lon:valid_max = 179.7624f ;
>                 nav_lon:long_name = "Longitude" ;
>                 nav_lon:nav_model = "Default grid" ;
>         float nav_lat(y, x) ;
>                 nav_lat:units = "degrees_north" ;
>                 nav_lat:valid_min = -90.f ;
>                 nav_lat:valid_max = 90.f ;
>                 nav_lat:long_name = "Latitude" ;
>                 nav_lat:nav_model = "Default grid" ;
>         float presnivs(presnivs) ;
>                 presnivs:units = "mb" ;
>                 presnivs:valid_min = 388.2434f ;
>                 presnivs:valid_max = 100426.5f ;
>                 presnivs:title = "presnivs" ;
>                 presnivs:long_name = "Vertical levels" ;
>         float time_counter(time_counter) ;
>                 time_counter:units = "seconds since 1990-07-02 
> 00:00:00" ;
>                 time_counter:calendar = "360d" ;
>                 time_counter:title = "Time" ;
>                 time_counter:long_name = "Time axis" ;
>                 time_counter:time_origin = " 1990-JUL-02 00:00:00" ;
>         float rain(time_counter, y, x) ;
>                 rain:units = "mm/day" ;
>                 rain:missing_value = 1.e+20f ;
>                 rain:valid_min = 1.e+20f ;
>                 rain:valid_max = -1.e+20f ;
>                 rain:long_name = "Precipitation" ;
>                 rain:short_name = "rain" ;
>                 rain:online_operation = "ave(X)" ;
>                 rain:axis = "TYX" ;
>                 rain:interval_operation = 1800.f ;
>                 rain:interval_write = 86400.f ;
>                 rain:associate = "time_counter nav_lat nav_lon" ;
>         float evap(time_counter, y, x) ;
>                 evap:units = "mm/day" ;
>                 evap:missing_value = 1.e+20f ;
>                 evap:valid_min = 1.e+20f ;
>                 evap:valid_max = -1.e+20f ;
>                 evap:long_name = "Evaporation" ;
>                 evap:short_name = "evap" ;
>                 evap:online_operation = "ave(X)" ;
>                 evap:axis = "TYX" ;
>                 evap:interval_operation = 1800.f ;
>                 evap:interval_write = 86400.f ;
>                 evap:associate = "time_counter nav_lat nav_lon" ;
>  // global attributes:
>                 :Conventions = "GDT 1.2" ;
>                 :file_name = "histday.nc" ;
>                 :production = "An IPSL model" ;
>                 :TimeStamp = "2005-MAR-17 09:44:56 GMT+05-3" ;
> }
>
> Thanks for any suggesions and help
>
> with regards,
> Ramesh
>
> --
> -----------------------------------------------------------------------
> Dr. K.V. Ramesh 
> Scientist 
> CSIR Centre for Mathematical Modelling and Computer Simulation (C-MMACS) 
> NAL Belur Campus, Bangalore - 560 037, India.
> E-mail: ramesh@cmmacs.ernet.in, kvram55@yahoo.com
> -----------------------------------------------------------------------
>
>