Default behavior of `assert_zero_transport` is misleading for regional domains

[hdrake]

I added the following line to assert that the total convergent transport is zero if no region is provided, in which case it is inferred that the region is the entire domain. I did this because I had in mind domains with either no-normal-flow boundary conditions or periodic boundary conditions, in which case this is a good assumption.

xwmb/xwmb/budget.py

Line 106 in 945d7d1

self.assert_zero_transport = True

However, @NelsonPoumaere pointed out that this gives the incorrect result for the total convergent transport in regional domains with open boundary conditions.

Maybe this line should be removed.

[hdrake]

@NelsonPoumaere, as a temporary workaround, you just set assert_zero_transport to False right after you create the xwmt.WaterMassBudget instance.

wmb = xwmb.WaterMassBudget(grid, xbudget_dict)
wmb.assert_zero_transport = False