Metro announced plans yesterday to lease air rights above its future subway station at Connecticut Avenue and Van Ness Street NW for a nine-story office and retail development.

As a byproduct of the multimillion-dollar project, Washington will get its first completely indoor bus-subway transfer station, permitting passengers to change between vehicles sheltered from bad weather. Such stations are a basic feature of the successful transit system in Toronto, often cited as a model for Washington.

The development atop Metro's Van Ness station will be on the west side of Connecticut Avenue between Veazey and Yuma Streets NW. It will adjoin the Washington Technical Institute campus of the University of the District of Columbia, directly opposite the Van Ness Center apartment and commercial complex.

The nearly rectangular site, now occupied by construction equipment, is 365 feet long and nearly 200 feet wide, containing 65,662 square feet of space. Metro bought it in 1975 for $2.8 million and now values it as high as $3 million. Officials hope to collect annual land rent of more than $200,000, with that figure rising as the project becomes more profitable to the developer.

The Metro Transit Authority expects to choose the developer in the same fashion as it did for a smaller downtown site on the northwest corner of Connecticut Avenue and L Street NW, atop the Farragut North subway station. A renewable 50-year lease is being proposed.

At Farragut North, would-be developers were invited to submit their proposals for development financial packages. The winner was developer-attorney Gerald J. Miller, who is now erecting a 13-story building scheduled for occupancy in April.

Metro's real estate office said a propectus for potential de velopers at Van Ness will be issued later. The present to Van Ness by late 1980. The air rights site would become available to the private developer late in 1989.

Under Metro's proposal, five bus bays and 25 so-called "kiss-and-ride" automobile spaces would be constructed directly atop the subway station.

Present zoning for commercial development permits a 60-foot-high (or six story) building on the site. Ben W. Gilbert, D.C. municipal planning director, said the city's Zoning commission would welcome a so-called "planned unit development," permitting construction generally up to 90 feet (nine stories).

The Van Ness station is the farthest from downtown of three subway stations being built on Connecticut Avenue west of Rock Creek Park.Beyond the Van Ness station, the subway line swings west to Wisconsin Avenue and will run to Bethesda, Rockville and Shady Grove.