The architectural pomp surviving from Liverpool's Victorian heyday as a port may look a little bloated from a post-imperial perspective, but it hardly deserves the indignity of the ugly shopping centres that have mushroomed in the city's commercial centre. Elsewhere, its architectural heritage has fared rather better, nowhere more spectacularly than down on the docks, where the monumental, functional redbrick buildings have found a new lease of life. They now house the Beatles Museum, the Maritime Museum and the Liverpool Tate.

When it was established 10 years ago, the Tate of the North was an ambitious venture, and Liverpool was a more depressed place than it is today. Despite sluggish beginnings, the gallery established itself as an integral component of the revitalised docklands, so much so that last year it closed for substantial refurbishment and expansion. When it reopened at the end of May it had some 30 per cent more exhibition space, chiefly in two expansive top-floor galleries with beautiful natural light.

Initially they were occupied by a group exhibition, but now the first one-person show to be installed there has opened. Not only was this honour accorded to an artist from Northern Ireland, Willie Doherty, but his exhibition is also the largest of his work to date, spanning the last 10 years of his output and including a major new audiovisual piece that gives the show its title: Somewhere Else. Not yet 40, Doherty has perhaps the highest international profile of any Irish artist. He has exhibited extensively at home and abroad, showing for many years with the Oliver Dowling Gallery in Dublin, and latterly with the Kerlin. Shortlisted for the Turner Prize in 1994, he went on to win the IMMA/Glen Dimplex Artist's Award the following year.

He works with photography, text, and audiovisual installations. He established his reputation with a series of black-and- white photo-text works in which the terse, superimposed captions indicated the submerged and opposed meanings contained in the images. Almost invariably, the images explored the terrain within and surrounding his native Derry.

There were never any people in these photographs, yet the human presence was implicit, whether because they depicted the often bleak urban environment and the direct signs of conflict or because, in the case of rural, apparently neutral scenes, the captions underscored the way the landscape was politicised through ideological appropriation and representation. Stone Upon Stone, for example, consists of two photographs designed to hang on opposite sides of a corridor. They depict the east and west banks of the Foyle, each bearing slogans of, respectively, Loyalist and Republican identity.

Doherty was prompted by his dissatisfaction with the images of Derry that were offered for public consumption. His work drew extensively on his own local knowledge, and it wasn't at all a question of depicting a "normality" behind the ubiquitous images of strife, rather a means of contextualising those images, and pointing up the complexity of the realities they failed to deal with. Often he does so by putting limits on what we can see: the city in darkness in Critical Distance, or a strip of waste ground deep in shade beside a brilliantly illuminated garage. "People have these two notions of Ireland," he said in an interview in 1988. "One is of it being quite romantic and beautiful, and also of it being the place where the troubles are happening." Throughout the last decade he has continued to deal with the co-existence of these views and their manifestations, particularly in media coverage of Northern Ireland. It's interesting that the relative emphasis of one or the other also waxes and wanes within his own work, particularly since he started using colour. In particular, his response to the beauty of the landscape, including the city's hinterland, comes through strongly in his sensitivity to the atmospherics of place, season and light.

And several years back he dispensed with those irritating, gnomic captions printed on the photographs, a dated, portentous device, without sacrificing density of meaning. It may seem paradoxical to speak of the melancholy charm of a photograph of a scarred barrier, brutally inserted onto a desolate rural by-road, but that's pretty much what he captures in Border Road II, apart altogether from the allegorical implications of the image.

These are rehearsed explicitly in a looped video piece, At the End of the Day, which takes us on an endlessly repetitive car journey along just such a by-road until we come face to face with the immovable obstacle of the blockade. Somewhere Else is both beautiful to look at and a technical tour de force of audiovisual installation. Four simultaneous large-scale video projections, on every surface of an L-shaped screen, are counterpointed by a commentary that shifts from speaker to speaker, prompting you to move around, to try to get some sort of overall view. We see and hear disconnected fragments of a possible narrative that never quite coheres: there is no overall view. Even the title is ambiguous. Is it the somewhere else where bad things happen, or the somewhere else where they do not happen? In this the piece conserves the logic of Doherty's recent work, which consistently strives to disorient its viewers. It does so by thrusting them into situations which deny them the habitual sense of control bestowed by narrative conventions. Or, for that matter, by the codes of representation which implicitly inform our understanding of, say, Northern Ireland.

This is starkly apparent in They're All the Same, in which contradictory terms of description, stereotypical of both individuals and country, are recited in a measured commentary against a projected newspaper image of Nessan Quinlivan. To put it crudely, on the one hand there is the propagandist, tabloid demonisation of the antagonist, on the other the sentimental truisms of grass-roots republicanism. One means of disorientation is to leave us unsure as to whether we inhabit the point of view of aggressor, victim or observer. In Tell Me What You Want two videos, on monitors situated opposite each other, feature commentaries by a man and a woman seen only in silhouette. The imagery is unrevealing. Events are alluded to, but as we watch we become progressively less sure what has been done to whom, by whom - though we are in no doubt that something terrible has happened. Similarly, in the chilling The Only Good One is a Dead One we adopt the perspective of both assassin and victim.

In Somewhere Else we see, variously, a night-time road rushing towards us, an ambiguous blur of distant electric lights, a forest by day, waves breaking on a rocky beach, a roadside, a derelict interior. We hear details of personal impasse, a crime, a dream. With its elliptical style and its thrillerish, cinematic borrowings it makes up a distinctly Godardian mixture of high aesthetics and genre conventions. Rather than a sequential, closed narrative, we are presented with a number of possibilities, including the diametrically opposed ones of violent death and definitive escape. But then, as the unreliable narrator asks rhetorically at one point: "Who said things were going to be simple?"

Willie Doherty: Somewhere Else continues at the Tate Gallery Liverpool until October 4th.