[gradsusr] How to get the the Laplacian of Divergence?

[Joseph Basconcillo]

1. I used hdivg(var1,var2) to get the divergence of U,V wind components. But I also want to get the laplacia of the divergence, how can this be done in GrADS?

2. I want to plot a line/contour exactly equal to 0. My values range from -3 to 3. So when I try to set gxout contour there's a line equal to zero when I set clevs 0. I just to get the zero contour line or the center of that contour line where I presume the absolute zero is located.