Levy II, H., P. S. Kasibhatla, W.
J. Moxim, A. A. Klonecki, A. I. Hirsch, S. J. Oltmans, and W. L. Chameides,
1997: The global impact of human activity on tropospheric ozone.
Geophysical Research Letters, 24(7), 791-794. |
Abstract: Within a conceptual framework of stratospheric injection,
CO-CH4 background tropospheric chemistry,
parameterized pollution production in the continental boundary layer and
surface deposition, we use an 11 level GCTM to simulate global distributions
of present and pre-industrial tropospheric O3.
The chemistry is driven by previously simulated present and pre-industrial
NOx fields, while prescribed fields
of CO, CH4 and H2O
are held constant. An evaluation with measurements from 12 surface sites,
21 ozonesonde sites and 1 aircraft campaign finds agreement within +/-
25% for 73% of the observations while identifying systematic errors in
the wintertime high-latitude Northern Hemisphere (NH), the Southern Hemisphere
(SH) tropics during biomass burning, and the remote SH. We predict that
human activity has increased the annual integral of tropospheric ozone
by 39% with 3/4's of that increase in the free troposphere, though the
boundary layer [BL] annual integral has increased by 66%. The 2 largest
components of the global O3 budget are
stratospheric injection at 696 TgO3/yr,
and loss through dry deposition, which increases from 459 TgO3/yr
to a present level of 825 TgO3/yr. While
tropospheric chemistry's net contribution is relatively small, changing
from a pre-industrial destruction of - 236 TgO3/yr
to a present production of + 128 TgO3/yr,
it is a balance between two much larger terms, - 558 TgO3/yr
of destruction in the background troposphere and + 686 TgO3/yr
of production in the polluted boundary layer. Human impact on O3
predominates in the summertime extratropical NH and in the tropics during
their biomass burning seasons [increases of 50% - 100% or more]. Conversely,
there has been little increase in most of the upper troposphere [<20%],
where ozone's influence on tropospheric climate is strongest. |