Dobson Units
given the number density, N, in molecules per cm3 then
Note that = q · t = N · <mw> /Na where q is the volumetric mixing ratio of the species being measured.
To convert to mass column density, M, in grams per cm2
where N0 is Loschmidt's number.
The atmosphere consists of fixed gases (e.g., CO2,
N2O, CO), water, and ozone so the pressure within any level
is given as
so that
we can also define the total column density as
and if we require
then,
Ct(L) in eqn 6 and <mw> can be solved for iteratively with an initial guess of <mw> = <mw>f
The volumetric mixing ratio, i.e., molecules of species x to the total number of molecules, is given by