She meets challenges that go back at least to Kline and Pollock

CLOUDS are among the easiest of all things to paint, and among the most difficult to turn into art. Almost all attempts to do so have resulted in pretty pictures with little if any human or artistic significance. But that should come as no surprise. Clouds, after all, no matter how beautifully painted, have little bearing on human ideas, ideals, or realities.

Some excellent paintings of clouds do exist, however. Constable and Turner made small oil and watercolor studies of cloud formations in order to understand how they were formed and how they related to stationary objects on the land. And any number of other landscape painters in Europe and America have produced detailed studies of clouds to aid them in their understanding of light, atmosphere, and the elements.

None, however, has made clouds the primary subject of his or her art. All have felt that the inclusion of the horizon and some indication of fields, hills , or cities were essential if their work was to be of interest or have artistic relevance.

Knowing this, I was surprised several months ago to discover that Karen Gunderson, a young American artist, was currently painting pictures of clouds to the exclusion of everything else - and even more surprised to learn that they were considered art by several members of the art community.

I wasn't totally convinced at first. She was obviously serious about what she was doing, and the results were handsome and effective enough. Even so, something was lacking. Her paintings of clouds seemed more like large, tentative studies than completely realized works of art.

That perception ended dramatically, however, when I saw her recent New York exhibition. Most of it represented what I already knew, but the rest - especially several large, recent canvases - was so superior to her other efforts that it was obvious she had made a quantum leap forward in only a few months' time.

Not only were these newer works well painted, they were also dynamic and fully realized. More important, they dealt successfully with formal ideas that have challenged the art world at least since the days of Kline and Pollock, and they did so through a subject matter never before taken quite seriously.

What Gunderson had done was simple. Yet it made all the difference. By playing the sky and the clouds off against each other (rather than using the sky as a backdrop as was previously the case), she established a formal context within which opposites and contradictions - in the form of brilliant, light-drenched clouds and deep-blue skies - could meet, clash, and resolve themselves into stunning icons of wholeness.

Particularly significant was that the result wasn't merely a formalized depiction of this resolution but an image that could be enjoyed for itself alone.

In other words, these recent works can be viewed merely as beautiful paintings of clouds cascading through the sky, opening up to reveal a narrow, meandering sliver of blue, or building up to mountainous proportions against a vast expanse of space. But, even if that is the way these works are perceived, the viewer, thanks to the artist's concern that these images be presented within a larger framework, will still somehow sense that there is more to them than meets the eye.

Thus Gunderson someday is likely to join the long line of landscape painters from Claude Lorrain to Cezanne, Marin, and Burchfield for whom the appearances of nature are outward manifestations of privately and culturally significant ideals. And for whom art is not merely the flat-out depiction of pictorial ideas but the dynamic embodiment of those ideas within highly charged and generative forms, symbols, or images.

Especially impressive is the fact that this contrapuntal tension and formal resolution take place not only within individual paintings but between certain works as well. Hung by itself, ''Mountain Sky'' is a dramatic and stunning work seven feet high and nine feet wide. Placed next to ''Sky Falls,'' however, it immediately assumes a highly aggressive role and brings out the subtle, more inward realities that characterize this much narrower image.

I was also struck by how beautifully these two paintings would hold up next to a major canvas by Franz Kline and by how well they would represent a more feminine version of the ''resolution of contradictions'' so crucial to Kline's very masculine approach to art. His painting would project more ''noise''; hers, on the other hand, would strike a more holistic and quietly healing note.

It's still too early to tell how far Karen Gunderson can carry her art and what more she can do with it. The potentials of this work are great - even though it still looks a trifle raw and primitive, and her color suffers a bit from being so purely local. But that's about all I'd venture to say. After all, she surprised me once before by moving ahead at an extremely rapid rate - and I fully expect she will do it again.