data. If no measurements of M2/Mz are available, in that height range, then 2

* is calculated by

combining eqs. (8) and (20). 2

* is not used in the CBL.

Figure 5 shows the inverse height dependency of M2/Mz in the SBL. To create this curve we

assumed that: Zim=100 m; and therefore, Zi 2 =100 m; L=10 m; u*=.124, which is consistent with

a mixing height of 100 m; Tref = 293 K; and therefore based on eq. (11) 2

* = 0.115 K. These

parameter values were chosen to represent a strongly stable boundary layer. Below 2 m M2/Mz is

persisted downward from its value of 0.228 K m-1 at 2m. Above 100 m M2/Mz is allowed to decay

exponentially with height.

 

4.1.4 POTENTIAL TEMPERATURE PROFILING

For use in plume rise calculations, AERMOD develops the vertical profile of potential

temperature from its estimate of the temperature gradient profile First the model computes the

potential temperature at the reference height for temperature (i.e., zTref) as

 

where z z z and zbase is the user specified elevation for the base of the temperature msl ref base = +

profile (i.e., meteorological tower). Then for both the CBL and SBL the potential temperature is

calculated as follows:

where is the average potential temperature gradient over the layer )z. Note that for z <

zTref , )z is negative.

4.1.5 VERTICAL TURBULENCE CALCULATED

In the CBL, the vertical velocity variance or turbulence (F 2

wT) is profiled using an expression

based on a mechanical or neutral stability limit (Fwm % u*) and a strongly convective limit (Fwc %

w*). The total vertical turbulence is given as:

This form is similar to one introduced by Panofsky et al. (1977) and included in other dispersion

models (e.g., Berkowicz et al. (1986), Hanna and Paine (1989), and Weil (1988a)).

The convective portion (F 2

wc ) of the total variance is calculated as:

 

 

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