AERMOD View – Potential Temperature Profile Elevation
October 2017
The AERMOD air dispersion model generates a gridded vertical profile of potential temperatures. Since potential temperature is dependent on the elevation above mean sea level (MSL), the Meteorology Pathway (ME) in the model input file contains the required keyword PROFBASE.
In AERMOD View, this is set as the Surface Station Primary Met Tower in the Meteorology Pathway:
It is often not well understood what exactly potential temperature is or how the model utilizes this information.
Potential Temperature
The concept of potential temperature is used by the AERMOD model to simplify calculations. Note that pressure, temperature, and air density are inversely proportional to height changes. Potential temperature allows air temperatures at different altitudes to be compared using a standard level, avoiding the complexity introduced by the change in altitude.
Potential temperature (?) is the temperature that a parcel of air would have if it was adiabatically (without adding or removing heat) brought to 1000 mbar of pressure, as shown in the figure below.
Potential Temperature
The concept of potential temperature is used by the AERMOD model to simplify calculations. Note that pressure, temperature, and air density are inversely proportional to height changes. Potential temperature allows air temperatures at different altitudes to be compared using a standard level, avoiding the complexity introduced by the change in altitude.
Potential temperature (?) is the temperature that a parcel of air would have if it was adiabatically (without adding or removing heat) brought to 1000 mbar of pressure, as shown in the figure below.
Reference Temperature
AERMOD calculates a vertical profile of potential temperatures, primarily for use in the calculation of plume rise. This profile is calculated from a reference temperature, measured at the primary tower, which is typically the surface station.
In order to use this reference temperature to calculate the profile, it must first be converted to a potential temperature. To convert the reference temperature into a potential temperature, it is necessary to know at what pressure the temperature was measured, which in turn is dependent on the elevation above mean seal level (MSL). This is why the base elevation of the primary meteorological tower above MSL is required by AERMOD.
AERMOD calculates a vertical profile of potential temperatures, primarily for use in the calculation of plume rise. This profile is calculated from a reference temperature, measured at the primary tower, which is typically the surface station.
In order to use this reference temperature to calculate the profile, it must first be converted to a potential temperature. To convert the reference temperature into a potential temperature, it is necessary to know at what pressure the temperature was measured, which in turn is dependent on the elevation above mean seal level (MSL). This is why the base elevation of the primary meteorological tower above MSL is required by AERMOD.
