Dressed in a flannel shirt, red jacket, and knit winter hat, Jim Greene led one of 48 volunteer teams into Downtown Crossing on a chilly night Wednesday as the city set out to conduct its annual count of the homeless population, as well as to offer them aid, shelter, and medical assistance.

Greene, director of emergency shelters for the Boston Public Health Commission, ­approached two homeless women on Washington Street and was greeted by a warm, “Hey, Jim!” He has been working with the homeless for 27 years.