Re: units conversion

[Paul van Delst <pvandelst(at)ncep.noaa.gov>]

Craig Markwardt wrote:
> 
> Jason Li <jylimd@yahoo.com> writes:
> > Hi,
> >
> > MODTRAN package outputs atmospheric profile in tape 6. The physical unit
> > used for the gas concentration is in ATM CM/KM.  I want to convert it to any
> > one of the following units:
> >
> > g/Kg
> > ppmv,
> > g/m3
> >
> 
> I'm still wondering: what's the big deal?  If you need three
> conversions, then you can probably figure the scale factors once for
> all three and just put them in your code.  [ It must be harder than
> this. ]

It is a big deal and it is harder than that. Units conversion, particularly for the
numerous and arcane ones used in various meteorological and atmospheric spectroscopic
fields, is a lot more trickier than people think. Particularly when integrated quantities
are involved and interpolations must be performed etc. 

> In fact, given that that this was cross-posted to
> meteorology, is it even related to IDL at all?

Maybe he reads the MODTRAN output in IDL for plotting the results.

paulv

-- 
Paul van Delst           A little learning is a dangerous thing;
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pvandelst@ncep.noaa.gov                   Alexander Pope.