Montgomery County's outspoken Police Chief Robert J. diGrazia was fired yesterday by County Executive Charles Gilchrist, who said that the chief "was no longer effective" in part because of his persistent disparaging remarks about police officers.

"My purpose now is to clear the air...," Gilchrist said at a hastily called press conference yesterday, adding that it was time for the police department to "get out of this circus-like atmosphere and get back to work."

Gilchrist said that the 50-year-old diGrazia had been placed on administrative leave as of noon yesterday and that the ousted chief would continue to receive his $52,811 salary for as long as necessary until he "can straighten out his affairs."

Maj. Donald E. Brooks, 52, a reserved, quiet-mannered veteran whom diGrazia tried to fire in 1977, was named the acting chief yesterday. Brooks, who has served on the county force for 28 years, will hold that post for about six months but has asked to retire after that time Gilchrist said.

DiGrazia would make no comment yesterday on his firing or his future plans.

One of the first indications of the chief's impending departure came Wednesday evening when an aide to the new county executive called the chief's home and summoned him to yesterday morning's meeting.

At that meeting, Gilchrist first gave diGrazia the opportunity to resign. When the chief refused, Gilchrist fired him. Yesterday's announcement was the culmination of weeks of persistent rumors that diGrazia would soon be out of a job. The rumors were fueled by growing, often vocal, discontent among the department's 750 officers, many of whom objected to diGrazia's style, policies and philosophy of policing.

Gilchrist's action, however, appeared to stem chiefly from a disagreement with diGrazia's style of management, and not from any objection to his policies. "I think he had some good ideas," said Gilchrist, noting that he does not expect Brooks to make any drastic policy changes in the department.

Gilchrist, in virtually the only controversial pronouncement during his campaign for county executive, had expressed reservations about diGrazia's administration of the police department as early as last August. What apparently triggered yesterday's action, though, was a statement diGrazia made at a public forum three weeks ago that most police officers "see the community as the enemy."

Several officers angrily disputed the chief's statement and the Fraternal Order of Police called upon him to clarify his remark. The chief said his comment referred to a universal police problem and was not meant as "an indictment of the Montgomery police."

Gilchrist also said he took issue with the chief's statement that 50 percent of all police officers are unqualified for police work.

Those statements, Gilchrist said, "made it difficult impossible in my opinion, for him to succeed" in his efforts to reshape the Montgomery department.

When diGrazia returned to his office yesterday morning after his firing, he was in "good spirits," according to his colleagues who saw him.

He shook hands and thanked the people who stopped by to wish him well. Then, according to one officer, diGrazia calmly got some cardboard boxes and packed away all the plaques and mementos he kept in his office from his years as a police official in Novato, Calif., St. Louis County, and Boston.

He took down the cardboard pig with a police badge he kept hanging on his door, called his wife to pick him up and dropped out of sight for the rest of the day.

DiGrazia came to Montgomery County in November 1976 amidst much fanfare, after extensive nation-wide search for an outsider who could make changes in the department. But the new chief spurred controversy within the department almost immediately, first by appointing a civilian to be his chief aide and later by appointing a woman civilian to head the police training academy.

These were two examples Gilchrist cited during his campaign as causing low police morale. Gilchrist also mentioned his dissatisfaction with the low number of promotions -- 15 -- that had been made in DiGrazia's two-year tenure.

After Gilchrist's election, an atmosphere of anxiety and anticipation seemed to pervade the police department from the chief's office down to the district stations, and the beat officers. But each time Gilchrist was questioned about deGrazia's future, he said he had not yet made his decision.

Yesterday, Gilchrist decided, was the "appropriate time" to make the announcement since he was scheduled to appear with deGrazia at a promotions ceremony tonight.

To appear on the same podium with diGrazia, Gilchrist feared, would be tantamount to giving his tacit approval to both the chief and the promotion plan, which Gilchrist had criticized.

Gilchrist also announced yesterday that the promotion ceremony had been canceled, but that the 100 officers involved would still get their promotions.

DiGrazia's firing met with mixed reaction from police officers interviewed yesterday, but if there was one overriding sentiment, it was relief.

"Maybe we've got a hurdle behind us and we can get on with doing the job we're supposed to be doing instead of accusing one another of various things in the media and airing our dirty laundry," said Capt. Ralph Robertson, commander of te Bethesda station.

Some officers said diGrazia's unpopularity may have been due in part to circumstances beyond his control. He took over at a time of budget constraints when the department was shrinking rather than expanding as it was in the late '60s.

In addition, his tenure coincided with a time of increased militancy among rank-and-file officers.

In contrast to the general attitude of relief among county police officers, many county residents reacted angrily to the firing. Phone calls to the county government were running two to one against the firing and kept telephone officers busy all day, according to county information officer Charles Maier.

Among his other goals, diGrazia had continually emphasized his wish to improve the relations between the police department and the community and had ordered increased human relations training for officers.

Recently, diGrazia had been the target of allegations of mismanagement by a citizen's group called Code Three, headed by the wife of a police officer. A county grand jury subsequently started looking into these allegations. Against the wishes of the county state's attorney, the grand jury had its term extended to coninue the investigation on its own.

Gilchrist's public criticism of diGrazia last August came just four days after the county's Fraternal Order of Police announced its "no-confidence vote" in diGrazia and the day before his endorsement interview with the Police Political Action Committee induced "hundreds" of officers disgruntled with the chief to work for Gilchrist, according to FOP president Lenny Simpson.

"They were making telephone calls and passing out literature," said Simpson. "He never gave us a commitment about diGrazia... but it was just a gut feeling (that Gilchrist would remove him) that we had."

Gilchrist said he would solicit applications for the police chief's position from both inside and outside the department. A primary contender for the job is considered to be Maj. Wayne Brown, who will be the only major and highest ranking officer in the department once Brooks leaves.

Brooks, a hunter and a horseman who is well known to the older officers, said he sees his new role as acting chief as that of a mediator. He said his top priority, at Gilchrist's request, will be to take a hard look at the career development program which is unpopular with many officers.

He said he is not interested in the chief's job permanently because "I feel 30 years on the job is long enough."