The Senate Appropriations Committee yesterday added more than $25 million in federal funds to the District of Columbia's fiscal 1984 budget to help relieve overcrowding at the D.C. jail, to add seven new judges to the 44-judge Superior Court and to study the controversial idea of a merit-pay system for District school teachers.

The action marks an unusually aggressive congressional approach to helping the city address pressing problems and is an indication that the new chairman of the Senate D.C. Appropriations subcommittee, Sen. Arlen Specter (R-Pa.), plans to use Washington as a testing ground for some initiatives being considered on the national level.

"We need to do more in the criminal justice system throughout the country, and we are starting here in the District of Columbia," Specter told reporters yesterday.

The appropriations panel approved the budget legislation yesterday and sent it to the Senate floor, where it may be considered as early as this week.

The House already approved its version of the city's $2 billion budget without the added funding for the corrections system or the merit-pay proposal. If the full Senate approves the changes, final budget amounts would have to be negotiated in a conference with the House. In addition, the law governing the operation of D.C. Superior Court would have to be amended to allow for additional judges to join the bench.

The Senate bill also would add funds for expanded educational and training programs for D.C. prisoners, aimed at making sure they can read and write and have a marketable skill before they are released.

While city officials in the past have fought hard against congressional meddling in District affairs, they said they were pleased with the changes made yesterday.

"He Specter has followed initiatives he wants us to take with dollars," said Betsy Reveal, the mayor's budget director. "Some of these proposals in the past would have been mandated but not funded."

D.C. Department of Corrections funding was increased by $22.3 million to help relieve overcrowding by housing some D.C. jail prisoners at federal facilities and to fund the training programs. An additional $2.8 million was provided for the Superior Court judges.

Specter said the additional money could provide between 200 and 500 beds for D.C. jail prisoners. The government is looking at underused capacity at federal facilities in the District, including St. Elizabeths Hospital and Bolling Air Force Base, as potential locations for a minimum-security jail.

D.C. officials face possible contempt of court charges if they fail to relieve the severe overcrowding at the D.C. jail, which was built to house 1,335 offenders but is now overflowing with 2,400 prisoners.

The overcrowding is also partly a result of a backlog of court cases that keeps prisoners in jail awaiting trial, and the additional Superior Court judges would attack the problem from that angle, Specter said.

Specter had wanted to include another $3.6 million to hire 21 new assistant U.S. attorneys to prosecute cases before the expanded Superior Court, but Appropriations Chairman Mark Hatfield (R-Ore.) insisted that this recommendation be referred to the subcommittee on commerce and justice which appropriates funds for all U.S. attorneys. Hatfield, a member of that subcommittee, said he would support the request, however.

Sen. John Warner (R-Va.) succeeded in adding an amendment directing the Federal Bureau of Prisons to do a feasibility study, to be completed by January 1984, on the possibility of building a new faciliity within the District to house prisoners now at Lorton prison in Virginia.

The bill allocates $1.5 million for the merit-pay study, to be carried out by the D.C. Board of Education. It also adds $900,000 for vocational rehabilitation funding, to bring this program to last year's levels. The board of education is to call in all interested parties on the merit pay issue, and in particular listen to objections raised by teachers unions, before coming up with a recommendation. Merit pay has been debated on the national level since President Reagan advanced the idea of rewarding teachers for outstanding work with increased pay. The National Education Association, the largest teachers' union in the country, has opposed the idea strenuously, arguing that decisions on merit pay would be too subjective.

Asked what he would like the board of education to recommend, Specter said he would like it to make its own conclusions. But when asked if he would like to see the District become a testing ground for the president's proposals on merit pay, he replied, "I do."

The committee adopted language approved by the House to insure that the city pays for streetlighting until it is decided whether this cost will be passed on to ratepayers, but it deleted House language requiring the city to come up with an additional $15 million to pay off its long-term debt.

The House District Committee, meanwhile, yesterday approved the transfer of RFK Stadium to D.C. government ownership and passed a bill giving the District parole authority over persons convicted of D.C. offenses but jailed in federal prisons. Prisoners in federal facilities have claimed that their parole reviews are harsher than those of prisoners at D.C. facilities.