Research Highlights March 2011 : Fiore et al.
Study by Arlene Fiore and co-authors on North American isoprene influence on intercontinental ozone pollution
Changing land-use and
climate may increase biogenic isoprene emissions, which could offset
the benefits from North American air pollution controls for both
domestic and European air quality (surface ozone). Both
anthropogenic and biogenic emission changes are reflected in peroxy
acetyl nitrate (PAN), which may serve as a more effective indicator
of intercontinental emission changes than ozone itself.
Percentage decrease (left) and increase (right) in surface O3
(top), PAN at 700 hPa (bottom), resulting
from 20% decreases in NA anthropogenic O3
precursor emissions (left) and 20% increases in biogenic isoprene
emissions (right) in the MOZART-2 model during August of 2001. Note
the bottom color scale is doubled. Areas in white fall below the
minimum value shown. Over
intercontinental distances, in summer and fall, the NA isoprene
influence on ozone in surface air over Europe and North Africa (EU
region) is at least half of that from NA anthropogenic emissions
(compare top left and right panels). Future increases in NA isoprene
emissions could thus offset decreases in EU surface O3
resulting from controls on NA anthropogenic
We also examine changes in
PAN at 700 hPa for two reasons: (1) this level should reside in the
lower free troposphere and thus reflect the composition of air masses
that are available to subside and mix into the continental boundary
layer, and (2) this altitude is a region of the atmosphere that can
be sampled with ground-based instruments in mountainous regions.
Both NA anthropogenic and isoprene emission changes exert a larger
relative influence on PAN at 700 hPa, as compared to surface O3
(compare top and bottom). This result implies that long-term PAN
measurements at high altitude sites may help to detect O3
precursor emission changes.