Geo Layout function

Function in the terrain Geo Layout:

18 00 00 [xx] 80 27 61 D0

xx = Some argument (usually 00). Values used:

01 = used in Cool Cool Mountain (area 1) and Snowman's Land (area 1). Produces the snow effect (??)
02 = used in Jolly Roger Bay (area 2) and Secret Aquarium.
0C = used in Lethal Lava Land (area 1), Bowser's Fire Sea and Bowser Second Battle
0D = used in Dire Dire Docks (area 1).
0E = used in Jolly Roger Bay and Dire Dire Docks (area 2).

What are the effects of this values?


Edited 18/11: These are very old notes. Probably only a good disassembly will help understand this function.