AERMOD Tech Guide

Gaussian Plume Air Dispersion Model

8.3.4 Calculating the Potential Temperature Gradient above the Mixing Height from Sounding Data

AERMET calculates d/dz for the layer above z as follows:

- If the sounding extends at least 500m above zi the first 500 meters above zi is used to determine d/dz above zi .

- If the sounding extends at least 250 meters above zi (but not 500m) then the available sounding above zi is used to determine d/dz above zi .

- AERMET limits d/dz above zi to a minimum of 0.005.

- If the sounding extends less than 250m above zi then set d/dz = 0.005 (a default value).