The path conditions are specified
in the *ATM section in the normal
except that the first .atm
file must contain only contain a single-level 'profile'
(or just a single *HGT value).
The actual value of the *HGT 'altitude' is only relevant if
subsequent .atm files contain full
profiles, in which case the values will be interpolated at the specified
altitude. So, for example, *HGT = 10km can be used to select
path conditions appropriate to 10km altitude from the profile.