This is usually represented by a shaded half-circle above some depiction of a horizon, such as hills or water.
The genre for this stylistic element depends on a combination of decorative technique, color, and element.
Cataloging Example for Depicted Sherd:
|Interior/Exterior||Location||Decorative Technique||Color||Stylistic Element||Motif|
|Interior||Proximal Rim||Painted, under free hand||Purple-Blue, Intense Dark||Setting Sun||Scene A|