On Wed, Aug 31, 2011 at 3:50 PM, Alexa Villaume <email@example.com>
Yes, you have it backwards. The first axis of O3 is the rows, while the second axis is the columns. Keep in mind that Python and NumPy follow C array conventions while Matlab (and IDL?) follow Fortran array conventions.
So, either transpose O3, or swap x and y in the call to contourf.