Division Calculation in favourable conditions

The ground effect in favourable conditions is calculated with the equation of A_ground,H , provided that the following modifications are made:

• If G_path ≠ 0

  1. (a)

     In the equation of A_ground,H , the heights z_s and z_r are replaced by z_s + δ z_s + δ z_T and z_r + δ z_r + δ z_T respectively where

     	${\mathrm{\delta z}}_s=a_0{\left(\frac{z_s}{z_s+z_r}\right)}^2\frac{d_2^p}{2}$	(2.5.19)
     	${\mathrm{\delta z}}_r=a_0{\left(\frac{z_r}{z_s+z_r}\right)}^2\frac{d_2^p}{2}$

     a_o =2 × 10^–4 m^–1 is the reverse of the radius of curvature

     $${\mathrm{\delta z}}_T=6\times {10}^{-3}\frac{d_p}{z_s+z_r}$$
  2. (b)

     The lower bound of A_ground,F depends on the geometry of the path:

     (2.5.20)

• If G_path = 0

  A_ground,F = A_ground,F,min

The height corrections δ z_s and δ z_r convey the effect of the sound ray bending. δ z_T accounts for the effect of the turbulence.

Ḡ_m may also be equal to either G_path or G′_path depending on whether the ground effect is calculated with or without diffraction, and according to the nature of the ground under the source (real source or diffracted). This is specified in the following subsections.

For a path (S_i,R) in favourable conditions without diffraction:

• Ḡ_w = G_path in equation (2.5.17);

• Ḡ_m = G′_path .

With diffraction, refer to the next section for the definitions of Ḡ_w and Ḡ_m .