Re: [Q] what is the energy consumption of several airliners ?

From:         felton@phoenix.Princeton.EDU (phil. Felton)
Organization: Princeton Univ.
Date:         01 Jun 96 16:32:35 
References:   1 2 3 4 5
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In article <airliners.1996.820@ohare.Chicago.COM>,
(Larry Stone) wrote:

> In article <airliners.1996.805@ohare.Chicago.COM>,
> felton@phoenix.Princeton.EDU (phil. Felton) wrote:
> >This is incorrect, the altitudes that are flown by commercial airlines are
> ><40000 feet.  The atmosphere up to the tropopause is well mixed and therefore
> >the altitude of emission is irrelevant, SSTs on the other hand fly higher and
> >NOx emissions there are of more concern.


> Two problems: 1) As Karl has already stated, many modern jets do go above
> 40,000. A week ago, I was on a 767 that cruised at 43,000. 2) I believe at
> certain times of the year, the tropopasue can be down as low as the
> low-30's putting a large percentage of jets cruising above the tropopause.

Firstly, I won't argue over an extra 3,000 feet!  Secondly, the tropopause
does get down to about 30,000 feet over the poles in winter but I would suggest
that this is a far cry from "a large percentage of jets...... above the T."

Note that total emission by jet aircraft of NOx is 0.25 TgN/yr, which has a
lifetime in the troposphere of about 1-7 days (removed rapidly as acid rain).
Compare this with 8 TgN/yr produced by lightning, 8 TgN/yr from soil and 20
TgN/yr from fossil fuel combustion.  Most of the NOx in the stratosphere
comes from the reaction of oxygen atoms with N2O (very stable in the tropo-
sphere, lifetime >100yrs).  The sources of N2O are mainly biological and lead
to 10 TgN/yr being destroyed in the stratosphere resulting in 1 TgN/yr of NOx
being formed in the stratosphere, which can decrease the ozone concentration.
>From these figures it can be seen that direct production of NOx above the
tropopause by jet aircraft is not significant at present.