The odors released by a relatively small source, such as a lagoon or storage pond, might resemble a trash fire or gas flare. Variation in odor plumes caused by weather factors. Weather factors can help predict dispersion of odors moving away from the farm. Categories of dispersion conditions, based on solar radiation, cloud cover, and wind speed, are given in Chart 1. Dispersion is greatest during the day and, for a given wind speed, increases with the amount of solar radiation striking the earth's surface.
Dispersion is poorest at night and, for a given wind speed, decreases as cloud cover decreases.
The effect of weather conditions on odor dispersion. Note that the first four categories for solar radiation are functions of sun angle and cloudiness amount. The plume shapes shown in Figure 1 assume the plume is travelling over a smooth, flat surface. Rarely is the terrain surrounding a farm perfectly flat and smooth. Landscape plays an important role in the movement of odor off-farm.