What does snow depth refer to?

Snow depth specifically refers to the vertical measurement of how deep the snow lies on a horizontal surface. It indicates the thickness of the snowpack, which can be important for various applications, such as weather forecasting, avalanche prediction, and understanding potential impacts on the environment and infrastructure.

The other options suggest different concepts: the total volume of snow in a region refers to a broader measure that isn't limited to vertical depth; the duration of snowfall over a period pertains to time rather than depth; and the weight of snow accumulated focuses on mass rather than how deep the snow is. Thus, only the definition of snow depth as a vertical measurement accurately captures the essence of what is being asked in the question.