The Australian's new role was confirmed when the team unveiled its new car earlier this month, though Doohan himself was absent as he completed Formula 2 testing in Bahrain.
Part of the Alpine Academy, it was a logical move since the 19-year-old is the leading candidate within the Alpine programme.
Doohan has already had F1 outings with the squad, driving in Free Practice 1 at both the Mexico City and Abu Dhabi Grands Prix last year, as well as the post-season test.
At the time, the F2 race winner played down the importance of landing the reserve driver title, reasoning his chances of graduating to F1 are better served by winning the feeder championship rather than having the reserve driver title.
Now charged with both, Ocon believes Doohan is a positive addition to the team.
“I think we obviously can't be in a better place with having Jack,” he said when asked about his new colleague by Speedcafe.com.
“He's obviously the most experienced guy in the Academy, which makes sense for the team to have him as reserve.
“He's been performing super well in Formula 2 last year and he's driven the [F1] car quite a bit in the past and has been with the team quite a lot, on simulator.
“I'm hoping we won't need him but for the team is probably a very good thing.”
Doohan was present during F1 pre-season testing in Bahrain, taking a watching brief from the Alpine garage while also fulfilling a number of marketing commitments for the team as part of his reserve driver role.
His racing season starts alongside the F1 year this weekend as Formula 2 takes in its first round at the Bahrain Grand Prix.