How is the convergence zone modeled in DW?

[Castout]

Wow so it's possible to get a contact at 90nm. Though the window is pretty short so it's not possible to track a target at convergence zone. Is this correct?. Thanks.

Got a couple questions. Simple doesn't necessarily mean brief. Just do not go into that doctoral paper discussion. . My head just jams whenever I see a mathematical formula. Beautiful women too. Built that way it seems. LOL

Is indirect detection possible below thermal layer/deep depth in convergence zone?
Is direct detection range better when cruising below thermal layer for detecting a below thermal contact(same layer) compared with cruising above thermal and detecting a contact above thermal(same layer)?

Btw what is a surface duct. How is it different from convergence zone in terms of detection especially indirect detection.

You see I hardly know anything about the sonar environment. So help this poor fellow will you. never too late to learn something.
My questions are both for the game and in RL.
Many many thanks before.