DIRECT SOURCE CONTRIBUTION TO CONCENTRATION CALCULATIONS  IN THE CBL

Following Weil et al. (1997), the concentration distribution for the horizontal state contribution to the direct plume is given by:

Here, _dj and _zj are the effective source height and vertical dispersion parameter corresponding dj zj  to each of the two distributions in eq. (65). The dispersion parameters (_y , _zl & _z2 ) resulting from the total turbulence are calculated using eqs. (85), and (98) thru (103). The subscripts 1 & 2 refer to the updraft & downdraft plumes respectively, and 

with a₁ and a₂ given by eq. (72). 1 2

In obtaining Eq.(69), we use an "image" plume to satisfy the no-flux condition at the ground, i.e., an image plume from a source at z_r = -h_s, which results in the exponential terms containing z_r  + _dj on the right-hand side of Eq.(69). The image source at z_r = -h_s results in a positive flux of material at z_r = z_i. To satisfy the no-flux condition there, an image source is introduced at z_r = 2  z_i + h_s, which then leads to a series of image sources at z_r = 2 z_i - h_s, 4z_i + h_s , -4z_i - h_s , etc. 

The height of the direct plume is given by the following expression

The second term in eq. (71) is the plume rise due to convection.

h is calculated using eq. (116), and 

Recall that _wT is an effective vertical turbulence component and is calculated from eq. (35). The parameters appearing in eq. (72) are given by.

and R is assumed to be 2.0 (Weil et al., 1997).

6 The AMS/EPA Regulatory Model AERMOD

6.1 General Structure of AERMOD Including Terrain
6.2 AERMOD Concentration Predictions in the CBL
      6.2.1 DIRECT SOURCE CONTRIBUTION TO CONCENTRATION  
              CALCULATIONS IN THE CBL
      6.2.2 INDIRECT SOURCE CONTRIBUTION TO CONCENTRATION  
              CALCULATIONS IN THE CBL
      6.2.3 PENETRATED SOURCE CONTRIBUTION TO CONCENTRATION 
              CALCULATIONS IN THE CBL
6.3 Concentrations in the SBL Calculated by AERMOD 
6.4 Estimation of Dispersion Coefficients 
      6.4.1 AMBIENT TURBULENCE FOR USE IN CALCULATING DISPERSION
      6.4.2 BUOYANCY INDUCED DISPERSION (BID) COMPONENT OF _ AND _
              y z
      6.4.3 COMPONENT OF DISPERSION COEFFICIENTS DUE TO 
              DOWNWASH
6.5 Plume Rise Calculations in AERMOD
      6.5.1 PLUME RISE IN THE CBL 
      6.5.2 PLUME RISE IN THE SBL
6.6 Source Characterization 
6.7 Adjustments for the Urban Boundary Layer

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