Dobson Units
![ident](https://pds-atmospheres.nmsu.edu/images/ident.gif)
given the number density, N, in molecules per cm3 then
![rho](https://pds-atmospheres.nmsu.edu/images/rho2.gif)
![ident](https://pds-atmospheres.nmsu.edu/images/ident.gif)
![integ](https://pds-atmospheres.nmsu.edu/images/integ.gif)
![appeq](https://pds-atmospheres.nmsu.edu/images/appeq.gif)
![Delta](https://pds-atmospheres.nmsu.edu/images/Delta.gif)
![Delta](https://pds-atmospheres.nmsu.edu/images/Delta.gif)
![rho](https://pds-atmospheres.nmsu.edu/images/rho2.gif)
![Delta](https://pds-atmospheres.nmsu.edu/images/Delta.gif)
Note that
![rho](https://pds-atmospheres.nmsu.edu/images/rho2.gif)
![rho](https://pds-atmospheres.nmsu.edu/images/rho2.gif)
To convert to mass column density, M, in grams per cm2
![Delta](https://pds-atmospheres.nmsu.edu/images/Delta.gif)
![sum](https://pds-atmospheres.nmsu.edu/images/sum.gif)
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
![Delta](https://pds-atmospheres.nmsu.edu/images/Delta.gif)
![ident](https://pds-atmospheres.nmsu.edu/images/ident.gif)
![integ](https://pds-atmospheres.nmsu.edu/images/integ.gif)
![rho](https://pds-atmospheres.nmsu.edu/images/rho2.gif)
![integ](https://pds-atmospheres.nmsu.edu/images/integ.gif)
![rho](https://pds-atmospheres.nmsu.edu/images/rho2.gif)
![rho](https://pds-atmospheres.nmsu.edu/images/rho2.gif)
![rho](https://pds-atmospheres.nmsu.edu/images/rho2.gif)
so that
![Delta](https://pds-atmospheres.nmsu.edu/images/Delta.gif)
![Delta](https://pds-atmospheres.nmsu.edu/images/Delta.gif)
we can also define the total column density as
![ident](https://pds-atmospheres.nmsu.edu/images/ident.gif)
![Delta](https://pds-atmospheres.nmsu.edu/images/Delta.gif)
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
![Delta](https://pds-atmospheres.nmsu.edu/images/Delta.gif)