Similar to how zoro and sanji kinda parallel each other by representing heaven and hell usopp and nami coincidentally have something similar going on
Usopp representing earth/land and nami representing air/sky
Usopp basically being a botanist. He has ties to Mont Blanc Noland who was also a botanist with usopp in a way walking in his footsteps. There’s a statue of him in skypia and green bit where plant life is a big aspect of both cultures. His training during the timeskip at boin archipelago was pretty much him upgrading his arsenal with plants. Plants are also likely to play a big part in elbaf culture too
Also originally there was supposed to be an official botanist in the crew with oda seemingly giving that role to usopp
Nami very obviously being tied to the weather from the jump. She the navigator of the crew and has had weather based attacks since alabasta
Her weather sensing abilities are basically super natural. I feel like she might also have some special lineage or at least some connection to some ancient person. Like zoro ryuma, sanji sora, and usopp Noland but idk to who