free grads

This function takes an areal average over an X-Y region. The syntax is:

aave(expr, xdim1, xdim2, ydim1, ydim2)

where:

expr    - any valid grads expression 
xdim1   - starting X dimension expression 
xdim2   - ending X dimension expression 
ydim1   - starting Y dimension expression 
ydim2   - ending Y dimension expression