Why are passive dispersion coefficients not typically provided for distances greater than 1 kilometer?

Passive dispersion coefficients are primarily designed to represent the behavior of pollutants over shorter distances, commonly up to around 1 kilometer. Beyond this range, their reliability diminishes due to a number of factors. As the distance increases, various environmental variables such as wind speed, atmospheric stability, and turbulence have a more significant impact on dispersion patterns.

The assumptions and simplifications that make the coefficients useful at short distances may no longer hold true under the complex interactions present over longer ranges. Consequently, their predictive accuracy can decrease, making them less dependable for application in scenarios involving greater distances. This notion underscores the importance of using dispersion models specifically tailored for longer distances, which incorporate a wider array of influencing factors and are designed to accommodate the variability inherent in atmospheric conditions.