In a literary work, atmosphere is the feeling that a particular location inspires.
In the short story "The Pedestrian," the atmosphere that is generated is one of estrangement and lifelessness. In the exposition of this story, Leonard Mead sets out on his nightly walk through uninhabited streets that are "silent," "long and empty," with only "his shadow to be seen."
If he closed his eyes and stood very still, frozen, he could imagine himself upon the center of a plain, a wintry, windless Arizona desert with no house in a thousand miles and only dry river beds, the street for company.
As Leonard continues this walk, he never encounters a single person on the sidewalks that he traverses. When he peers inside the lightless houses, Leonard knows that the occupants are sitting before their television sets in the dark, mindlessly watching some program. Leonard talks to them, but they do not hear; he is isolated from these desensitized people whose thoughts are but mirrors for some inane personage on a television program.
Throughout the narrative, words such as gray, silent, tomb-like, ill-lit, iron, and empty serve to connote the isolation of Leonard Mead and create the mood and atmosphere of isolation and loneliness in the story.