To calculate the cost distance between two points in a wind field, I have to make a cost surface. Then, I think , atmosphere stability a good indicator for this cost, because this indicates the speed at which air pollution can be dispersed and there is even some model using horizontal wind speed to determine the stability, but this model only classifies the stability into 5 classes. Now comes my question: to incorporate this index into the model I have to use to inverse of wind speed to estimate it, so how do I determine the power? Is there any application?