Every year, for one month only, the National Gallery exhibits its collection of 36 watercolours by Joseph Mallord William Turner (1775-1851). It is precisely because January is the darkest month of the year that they are displayed at this time. The aim is to ensure that they remain in their pristine condition, and it was one of the stipulations of the Vaughan Bequest, which donated 31 Turners to the gallery at the turn of the 20th century. They were first exhibited in 1901, and each new year since then Turner's jewel-like watercolours have been taken out of storage and put on public display.

This year, the exhibition, entitled 'Turner and the Traditionalists', attempts (rather half-heartedly) to set the renowned landscape artist in context with his British contemporaries. Turner's works are thus shown alongside watercolours by his peers from the gallery collection. But rather than giving any particular insight into the trends of the time and Turner's place within them, the exhibition merely highlights that these particular works are generally greatly inferior to Turner's. If anything, it underlines what made his work so revolutionary at the time, and why it remains so enduringly popular.

Turner was a master of atmosphere and light, while also accurately capturing topographical and local detail.

Even an early work such as The West Gate, Canterbury, Kent (c 1793) reveals an assured eye and delicacy of touch. The painting depicts the only surviving mediaeval gate at Canterbury - a dramatic structure seen from a low viewpoint and framed by the sky. While the precise underdrawing reflects the watercolour traditions of the time, the subtlety of the colours and attention to detail already set Turner apart.

In comparison, a London street scene by his teacher Thomas Malton the Younger is rather stiff, echoing architectural drawings. Likewise, Edward Dayes, who was similar in age to Turner, created a fine, preciselydetailed rendering of Southampton Harbour. However, it seems staid and lifeless in comparison to Turner's beautifully atmospheric Fishing Boats on Folkestone Beach, Kent (c 1828). This also features a boat coming ashore, but Turner manages to blend an accurate account of local activity - in this case fishing - with a magnificent, golden, sunlit sky. The sky echoes the classical landscapes of Claude Lorrain, who Turner greatly admired, and whose radiant skies he often sought to emulate. So too did George Barret the Younger in his Resting Shepherd in a Claudean landscape (1827), which is a pleasant, if staged, rendering of a classical landscape, complete with goats and a Romantic figure reading in the foreground.

Turner was renowned as a maritime painter and the sea was a subject he would return to again and again. While the Folkestone scene is peaceful and serene, Turner frequently depicted stormy, raging seas.

Nature for Turner was dangerous, unpredictable and powerful, as reflected in A Shipwreck off Hastings (c 1825), in which the remains of a destroyed ship bob on the crashing waves. His tiny A Ship against the Mew Stone, Plymouth (c 1814) is a dramatic depiction of a boat struggling against being dashed upon a craggy rock.

In comparison, Nicholas Pocock, a former sailor who became a professional painter, created a masterful, precisely detailed painting of ships off either Gibraltar or St Kitts in the West Indies. His approach is a more traditional one, reflecting man's control over nature, with the British fleet easily mastering the seas.

Turner, who was a frequent traveller throughout Britain and the continent, also evoked the awesome and the sublime aspects of nature in views of the Swiss mountains such as the broadly painted Montjovet from below St Vincent, looking down the Val d'Aosta towards Berriaz (c 1836). His treatment of mountains and the effects of the weather are absorbed by AVC Fielding and Samuel Austin, although both maintain an interest in clarity and detail at the expense of the atmospheric effects Turner had perfected.

Turner's late renderings of Venice are the watercolorist at his most sublime - and experimental.

A few dashes of paint or lines of red give accurate form to buildings otherwise suffused with atmospheric swathes of colour. His Capriccio with San Giorgio Maggiore (c 1840) is an impressionistic rendering of the lagoon island as a radiant, floating vision, burning with the intense red light of the setting sun.

Such a dose of Turner, with its rich, shimmering dashes of luminescence, would transform any one of these windy, wet January days.

'Turner and the Traditionalists' at the National Gallery of Ireland until 31 January