The man is described as around 30 years old, white, about 6ft, of medium build, with an unkempt appearance - as if he had been sleeping rough. He is thought to be have been wearing a black hooded top, a red, white and blue scarf, and grey or black hiking boots with thick laces.
Det Ch Insp Dunn said: "I am keen to speak to anyone who may have seen this man in the Bedford or Powis area around the time of the incident, or who may have information regarding his identity.
"This man may also have been in the Powis area on the morning of Friday October 26, so I am also interested in any sightings of a man fitting this description earlier in the week."
Police have also released a description of the victim to "encourage anyone who may have seen either of these people to come forward." Det Ch Insp Dunn said the woman was wearing a dark jacket and jeans and a black and white hat.
"This was a particularly nasty attack and with that in mind, although these incidents are rare in Aberdeen, I would encourage members of the public to take all reasonable precautions to protect their personal safety."