Not much of a surprise here, but today it finally becomes official: Henry Tirri has been appointed CTO of Nokia, nearly four months after assuming the position on a temporary basis. Tirri, who joined the company in 2004 and previously served as head of its research center, will permanently replace former CTO Rich Green, who took an indefinite leave of absence from Espoo back in June, citing "personal reasons." At the time, some local media outlets reported that Green's absence would be permanent, due to disagreements over CEO Stephen Elop's smartphone OS strategy. Reportedly a one-time Meego advocate, Green will now return to the US to "pursue new opportunities" and, as of today, is no longer a member of the Nokia Leadership Team. Tirri, meanwhile, will be responsible for designing "Nokia's technology agenda both now and in the future, and driving core innovation to enable business development opportunities." We'll have to wait and see where that path leads, but you can find more details about the appointment in the full press release, after the break.