Values for the dispersion coefficients are much easier to obtain experimentally
than eddy diffusivities.
The dispersion coefficients are a function of atmospheric conditions and the distance
downwind from the release. The atmospheric conditions are classified according to six different
stability classes, shown in Table 5-1. The stability classes depend on wind speed and quantity
of sunlight. During the day, increased wind speed results in greater atmospheric stability,
whereas at night the reverse is true. This is due to a change in vertical temperature profiles from
day to night.