convert ~/pencil-code/axel/forced/BruntVaisala/T128i_05/img_0000.png pnm/1.pnm
convert ~/pencil-code/axel/forced/BruntVaisala/T128i_005a2/img_0000.png pnm/2.pnm
convert ~/pencil-code/axel/forced/BruntVaisala/T128i_002b2/img_0000.png pnm/3.pnm
convert ~/pencil-code/axel/forced/BruntVaisala/T128i_0005b/img_0000.png pnm/4.pnm

cd pnm
pnmcat -lr 1.pnm 2.pnm 4.pnm > divu.pnm
convert divu.pnm divu.jpg
jpeg2ps divu.jpg > ../fig/divu.ps

