Comments on What is the distance (seasonal, directional) over which emissions influence NA sites?

What is the distance over which emissions influence nonattainment sites?

The lifetime of an ozone molecule in the atmosphere is inversely related in a nonlinearly way to the amount of fresh emissions encountered along its journey. For example, in the free tropophere, its lifetime is on the order of 3 months, at night above the nocturnal inversion layer, it could be 30 hours, but in a polluted area on a day conducive for ozone formation its lifetime is on the order of a couple of hours. Consequently, the answer to this question is less important in the development of control strategies then the answer to: "How far downwind can the benefits of emission reductions be measured? The regional impact modeling runs suggest that this varies from day to day and is considerably shorter than many anticipated.


Submitted by George Wolff on 9/17/96 RecID: GeorgeWolff

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Zone of Influence

Climatologically, it appears that 350-400 miles represents a
reasonable estimate of how far downwind one might expect the
emissions from one area to affect the resulting ozone in
another area. During any given episode, this distance may
shorter or longer. Given the fact that many urban areas are
closer to one another than this distance, their "zones of
influence" often overlap during any particular episode,
giving rise to extended effects of transport due to a
"piggybacking" effect, where one cities' emissions elevate
ozone (and precursor) levels at the next city downwind,
which can,in turn, further elevate ozone and precursor
levels at the next city downwind, and so on.

Submitted by David Guinnup RecID: DavidGuinnup1

Re: Zone of Influence

could you please send me info on tempature on the troposphere.:) on 3/5/01

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Re: Zone of Influence

I think the proposition that both precursor emissions and ozone itself originating in areas as far away as 350 to 400 miles affect ozone forming potential in urban (and rural) areas downwind of them is well supported by much of the OTAG analysis being carried out. My own impression, from non-causal associations we see in the patterns developed from statistical aggregation techniques applied to back-trajectories and also from some of the forward trajectory work being done at CAPITA, is that 400 miles understates the zone of influence substantially. Of course the notion of zone of influence needs to have some "significance level" for defining what is meant by "influence", and also transport may occur under a variety of met conditions. The diurnal (daylight/night-time) nature of the ozone formation and scavenging reactions as well as the level at which emissions may end up in the atmosphere certainly plays a role, as does the overall speed of transport in the synoptic scale motion. I would not hesitate to believe that emissions along the southern Mississippi River area might participate and contribute, under the right meteorological conditions, to the formation of ozone over the northeastern portions of North America. I don't think there is any evidence that indicates it is impossible for "any" such "influence" to occur at these distances, on the contrary, the current round of OTAG analyses seem to support such a contention.


Submitted by Paul Wishinski RecID: PaulWishinski

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