[curlz,cav] = curlm(lat,lon,U,V) computes the curl of U and V given their geographical coordinates lat and lon. lat, lon, U, and V must be m by n matrices of the same size. Coordinates given by lat and lon must be regular grids of latitudes and longitudes--that is, they must be separated as 120E, 121E, 123E, etc, not equally spaced in terms of kilometers of separation.