Bibliography - V. Naik
- Naik, V., A. M. Fiore, L. W. Horowitz, and H. B. Singh, et al., 2010: Observational constraints on the global atmospheric budget of ethanol. Atomsphere Chemistry and Physics Discussion, http://www.atmos-chem-phys-discuss.net/10/925/2010/acpd-10-925-2010.pdf, 10, 925-945
[ Abstract ]Energy security and climate change concerns have led to the promotion of biomass-derived ethanol, an oxygenated volatile organic compound (OVOC), as a substitute for fossil fuels. Although ethanol is ubiquitous in the troposphere, our knowledge of its current atmospheric budget and distribution is limited. Here, for the first time we use a global chemical transport model in conjunction with atmospheric observations to place constraints on the ethanol budget, noting that additional measurements of ethanol (and its precursors) are still needed to enhance confidence in our estimated budget. Global sources of ethanol in the model include 5.0 Tg yr−1from industrial sources and biofuels, 9.2 Tg yr−1 from terrestrial plants, ~0.5 Tg yr−1 from biomass burning, and 0.05 Tg yr−1 from atmospheric reactions of the ethyl peroxide radical (C2H5O2) with itself and with the methyl peroxide radical (CH3O2). The resulting atmospheric lifetime of ethanol in the model is 2.8 days. Gas-phase oxidation by hydroxyl radical (OH) is the primary global sink of ethanol in the model (65%), followed by dry deposition to land (25%), and wet deposition (10%). Over continental areas, ethanol concentrations predominantly reflect direct anthropogenic and biogenic emission sources. Uncertainty in the biogenic ethanol emissions estimated at a factor of three may contribute to the 50% model underestimate of observations in the North American boundary layer. Furthermore, current levels of ethanol measured in remote atmospheres are an order of magnitude larger than those explained by surface sources or by in-situ atmospheric production from observed precursor hydrocarbons in the model, suggesting a major gap in understanding. Stronger constraints on the budget and distribution of ethanol and other VOCs are a critical step towards assessing the impacts of increasing use of ethanol as a fuel.
- Naik, V., D. L. Mauzerall, L. W. Horowitz, M. D. Schwarzkopf, V. Ramaswamy, and Michael Oppenheimer, 2007: On the sensitivity of radiative forcing from biomass burning aerosols and ozone to emission location. Geophysical Research Letters, 34(L03818), doi:10.1029/2006GL028149
[ Abstract ]Biomass burning is a major source of air pollutants, some of which are also climate
forcing agents. We investigate the sensitivity of direct radiative forcing due to
tropospheric ozone and aerosols (carbonaceous and sulfate) to a marginal reduction in
their (or their precursor) emissions from major biomass burning regions. We find that the
largest negative global forcing is for 10% emission reductions in tropical regions,
including Africa (-4.1 mWm-2 from gas and -4.1 mWm-2 from aerosols), and South
America (-3.0 mWmfrom gas and -2.8 mWmfrom aerosols). We estimate that a unit
reduction in the amount of biomass burned in India produces the largest negative ozone
and aerosol forcing. Our analysis indicates that reducing biomass burning emissions
causes negative global radiative forcing due to ozone and aerosols; however, regional
differences need to be considered when evaluating controls on biomass burning to
mitigate global climate change.
- Naik, V., D. L. Mauzerall, L. W. Horowitz, M. D. Schwarzkopf, V. Ramaswamy, and Michael Oppenheimer, 2006: Net radiative forcing due to changes in regional emissions of tropospheric ozone precursors. Journal of Geophysical Research, 110(D24306), doi:10.1029/2005JD005908
[ Abstract ]The global distribution of tropospheric ozone (O3) depends on the emission of
precursors, chemistry, and transport. For small perturbations to emissions, the global
radiative forcing resulting from changes in O3 can be expressed as a sum of forcings from
emission changes in different regions. Tropospheric O3 is considered in present climate
policies only through the inclusion of indirect effect of CH4 on radiative forcing through
its impact on O3 concentrations. The short-lived O3 precursors (NOx, CO, and NMHCs)
are not directly included in the Kyoto Protocol or any similar climate mitigation
agreement. In this study, we quantify the global radiative forcing resulting from a marginal
reduction (10%) in anthropogenic emissions of NOx alone from nine geographic regions
and a combined marginal reduction in NOx, CO, and NMHCs emissions from three
regions. We simulate, using the global chemistry transport model MOZART-2, the change
in the distribution of global O3 resulting from these emission reductions. In addition to the
short-term reduction in O3, these emission reductions also increase CH4 concentrations
(by decreasing OH); this increase in CH4 in turn counteracts part of the initial reduction in
O3 concentrations. We calculate the global radiative forcing resulting from the regional
emission reductions, accounting for changes in both O3 and CH4. Our results show
that changes in O3 production and resulting distribution depend strongly on the
geographical location of the reduction in precursor emissions. We find that the global O3
distribution and radiative forcing are most sensitive to changes in precursor emissions
from tropical regions and least sensitive to changes from midlatitude and high-latitude
regions. Changes in CH4 and O3 concentrations resulting from NOx emission reductions
alone produce offsetting changes in radiative forcing, leaving a small positive residual
forcing (warming) for all regions. In contrast, for combined reductions of anthropogenic
emissions of NOx, CO, and NMHCs, changes in O3 and CH4 concentrations result in
a net negative radiative forcing (cooling). Thus we conclude that simultaneous reductions
of CO, NMHCs, and NOx lead to a net reduction in radiative forcing due to resulting
changes in tropospheric O3 and CH4 while reductions in NOx emissions alone do not.
Direct link to page: http://cmi.princeton.edu/bibliography/results.php?author=3755
