Mr Greenway was last spotted at around 11pm on Saturday evening when he left his home on the Esplanade wearing only pyjamas.
Police sniffer dogs have been used this morning in a bid to pick up his scent and were seen in the area near to his home.
Jack Greenway is a keen environmentalist
Several officers are also sweeping Broughty Ferry Nature Reserve and Barnhill Rock Garden as well as speaking to neighbours.
Mr Greenway, a keen environmentalist often seen picking up litter from the beach and the rock garden in previous years, lives just metres from the dunes.
Officers search Reres Park on Monday
He is five feet eight inches tall with white hair, a white beard, and of slim build.
