Follow along

Want to follow along as I describe everything? Download this netcdf-format data file and let's get started.


Starting up

At the command prompt, just type "ncview" followed by the name of your netcdf file:

% ncview

Two windows will appear, the control window and the display window:

File information

The top part of the control window has information about the file. The first line displays the netCDF global attribute named "title":

In this case, the file lacks a global attribute named "title", so the version of ncview is shown instead.

The second line shows the name of the variable you are viewing:

If the netCDF variable has an attribute named "long_name", the long name is displayed here instead of the regular name of the variable.

The next line shows information about the unlimited dimension of the file, which is typically time:

In this example, there are 38 frames (timesteps) in the file, and we are currently looking at frame 1. Additionally, we see that frame 1 corresponds to the date "Jan 1 1966". Ncview will automatically recognize and decode time units that are compatible with udunits, which have a format similar to "days since 1900-01-01".

Next we have the range of the data in the file:

Which, in this case, shows us that the most "blue" colors correspond to -3.92 C, and the most "red" colors indicate 2.89 C. Ncview knows that the units are "C" because it reads in the "units" attribute of the variable.

Last, we have the line that shows where the cursor is in the data, and the data value under the cursor:

Go ahead and move the mouse cursor over the data -- you'll see the display change to show you the location and data value. Also, in the picture above, do you see how it says j=157 but y=67.5? That's because j=157 shows the Y index value (with the count starting at zero, not one!) while y=67.5 shows the coordinate value at that location, in this case, 67.5 degrees North.

Animating and moving in time

To animate your data, click on this button:

The display window will start showing a movie of the data. (If the movie goes too fast, slide the "Delay" slider to the right.) As the data animates,

(C) 2008 David W. Pierce