NCL: ROMS

WARNING: The ROMS data set is NOT on a native grid even though the data file contains info on how to plot it on a lambert conformal projection. The data still needs to be transformed to that projection. This is the default behavior of the plot templates.

These plots use the high resolution GMT coastline. This coastline does not bundled with NCL, but can be downloaded.

Ivica Janekovic (Rudjer Boskovic Institute, Zagreb, Croatia) has donated an NCL library of functions that facilitate writing cleaner scripts. The library is named ROMS_utils.ncl. The library may be downloaded here. The contents of the ROMS_utils.ncl library can be viewed via

         %> less ROMS_utils.ncl

roms_1.ncl: Basic color plot of the data w/o any changes to the projection.

ROMS data has 2D lat/lon coordinate info. We plot this differently than data with 1D coordinates. You need to set:

       lat2d     = f->lat-array
       lon2d     = f->lon_array
       t@lon2d   = lon2d
       t@lat2d   = lat2d

Where the the lat/lon arrays are particular to the variable, e.g. lat_rho

The three pieces of information that are required for a lambert conformal projection are: mpLambertParallel1F, mpLambertParallel2F, and mpLambertMeridianF

In order to zoom in on the Gulf of Alaska, we need to have the lower left and upper right corners of the grid. In our sample file this data was conveniently provided.
mpLeftCornerLatF, mpLeftCornerLonF, mpRightCornerLatF, and mpRightCornerLonF

roms_2.ncl: Changes the values of the corners provided by the model to zoom in just slightly.

roms_3.ncl: Example of drawing vectors.

roms_4.ncl: Use the roms_3d_interp function located in the ROMS_utils.ncl library to interpolate to a user specified level.

roms_5.ncl: Similar to the previous example but has a velocity overlay. Note: roms_3d_interp is working on "rho" coords. If you specify variable "u" or "v" it is transfering them first to the "rho" and than interpolate.