In the most intensive New York City manhunt in recent years, a special task force of 30 detectives is combing two boroughs for a lovesick, psychopathic killer who has shot to death four young women with shoulder-length brown hair in the past nine months.

Apart from electrifying the imagination of the headline writers of New York's tabloid newspapers, the killer has frustrated the efforts of the largest police department in the nation and has spread terror through some residential neighborhoods in the Bronx and Queens.

Although they have little more to go on other than sketchy and conflicting eyewitness descriptions and a rambling and incoherent note left at the scene of the last killing, police say they have pieced together a psychological composite that may lead them to a subject.

What is emerging from the evidence is a portrait of severely disturbed man in his mid or late 20s - possibly an Army veteran - whose recent rejection by a young woman hit on the raw would of a mother's rejection years ago.

Police are certain that when he kills, his feeling of gratification is only temporary, and that after a period of days or weeks, volano-like emotional pressure begins building up again to the point of retaliatory rage.

The murderer, dubbed "the .44-caliber killer" by New York's tobloids, his slain four women and one man and wounded four other persons in six separate shootings since last July 28. In four of the shootings, his victims were sitting in parked cars as he fired at them through a window or windshield with the Western-style revolver.

His most recent victims were Valentina Suriani, 18, a Lehman College student, and her boyfriend, Alexander Esau, 19, who were shot to death at 3 a.m. Sunday as they sat in a parked car in Pelham Bay park a block from her home.

The note left at the scene was said by police to have been rambling and incoherent, with a taunting tone - although authorities refused to detail its message.

In spite of the note and descriptions provided by some of the survivors, police claims they have little to go on and are still doing such fundamental investigating as sifting through records of known sexual offenders and interviewing officials of mental hospitals for information about patients with psychiatric histories of being women haters.

"We have some tips and some possibilities. But there is no suspect who is a real not possibility," said Chief of Detectives John L. Kennan.

What the police do know is that the kiler is white, a "loner," and an expert marksman who braces himself in a "military crouch" when he fires the lethal shots through the car windows.

The killer also may give an appearance of stern morality, possibly carrying a Bible or working as a Boy Scout leader, according to Dr. Emanuel F. Hammer, a leading forensic psychologist and former director of the Psychological Secion of the New York City Criminal Courts.

Hammer, in an interview, said the killer probably is paralled to the classic manic depressive - a man who after achieving the emotional "high" from killng a woman comes down to a "placid, low-key" state of mind and appears normal in every sense.

"He probably has suffered tremendously at the hands of a woman with these charateristics (long, brown hair)," Hammer said. "The rejection probably involved the flaunting of another man, perhaps in a parked car.

"But in any case, the rejection hit on an old wound of maternal rejection years ago, and the killings satisfy the exculpation of both traumas," Hammer said.

Harvey Schlossberg, the New York City police department's forensic psychologist said the fact that the killer has repeatedly shot some of his victims in the face may indicte a desire to "wipe out" a facial image of a woman who spurned his advances.

Hammer suggested that because the time between the killer's attacks is shortening, the man's condition is "getting more pronounced."

He also suggested that because the killer had left a note - "a major clue, no matter how you look at it" - he may subliminally want to be caught and imprisoned.

"This reflects less personality intergration. One would speculate that this disorder is so extreme at this stage, that the man wants to bring it all to an end," Hammer said.