Larry W. Horowitz
Research Page
I am a Physical Scientist
at the NOAA
Geophysical Fluid Dynamics Laboratory (GFDL).
My research focuses on the chemistry of tropospheric ozone
and related species. On this page, I describe the goals of my research,
and some of the techniques I use to address these goals.
View my MOZART-2 web page, describing the model I use in my research.
You can also view:
Ozone (O3) is of central importance to
the chemistry of the troposphere. Ozone is:
-
a major air pollutant, detrimental to public health and vegetations
-
the precursor of the hydroxyl radical, which is the primary oxidant in
the atmosphere
-
climatically-important greenhouse gas
Ozone is produced within the troposphere as the result
of reactions involving nitrogen oxides (NOx), carbon monoxide,
and hydrocarbons. Increases in the emissions of these ozone precursors
over the past century (from fossil fuel and biomass burning) are believed
to have resulted in increases in tropospheric ozone concentrations over
industrial regions, and probably on a global scale.
Major questions my research addresses include:
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What controls the global distribution of ozone in the troposphere?
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How have anthropogenic emissions altered the distribution of ozone?
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What role does deep convection in the tropics play in controlling the production
of ozone in the upper troposphere?
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What impact do changes in tropospheric ozone have on climate?
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How will projected future emission scenarios alter the chemistry of the
atmosphere?
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How does the oxidizing capacity of the atmosphere change in response to
varying anthropogenic emissions?
In order to answer these questions, I am using
a global three-dimensional chemical transport model (called MOZART)
to simulate the distributions of ozone and its chemical precursors throughout
the troposphere. Using MOZART, and comparing model results with observations,
I plan to test of our understanding of chemical and dynamical processes
in the atmosphere. A goal of my work is to improve our understanding of
the complex nonlinear dependence of ozone concentrations on emissions from
sources such as fossil fuel combustion and biomass burning.
The oxidizing capacity of the atmosphere, which is
the ability of the atmosphere to remove pollutants emitted, depends heavily
on the abundance of ozone in the tropics. However, there have been relatively
few measurements of ozone and its precursors in the tropical troposphere.
As a result, the mechanisms controlling ozone in this region are poorly
understood. Global three-dimensional models can be of great use in helping
to explain these mechanisms in a manner consistent with the few available
observations. Future land use changes and industrialization in the tropics
are expected to lead to an increased anthropogenic perturbation to ozone
in this region. There is a complicated interaction in the tropics between
surface emissions, convection, lightning, and large-scale circulation.
Using MOZART, which contains representations of all of these processes,
together with available observations of ozone and its precursors in the
tropics, I plan to study the mechanisms controlling the distribution of
tropical tropospheric ozone. I will also evaluate how well these various
processes are currently represented in global chemistry models.
I got my Ph.D. from the Atmospheric
Sciences Group in the Division
of Engineering and Applied Sciences at Harvard
University. My advisor was Professor
Daniel Jacob. In my dissertation research, I utilized a variety of
models to study tropospheric chemistry. In my early work, I used a photochemical
model to perform 0-dimensional and 1-dimensional simulations. I updated
our photo-oxidation mechanism for isoprene and studied the effects of these
modifications on the production of ozone and organic nitrates, using comparisons
with observations as a guide. I also developed a simplified chemical mechanism
for incorporation into a 3-dimensional chemical tracer model, and evaluated
the accuracy of this mechanism against our complete mechanism. I developed
and used both continental-scale and global versions of this model to study
the export of reactive nitrogen from the continental boundary layer and
its effect on the abundance of nitrogen oxides in the remote troposphere.
You can view my thesis
abstract and introduction (in pdf format).
Back to my Home Page
GFDL Home Page
Larry Horowitz / Larry.Horowitz@noaa.gov
Last modified: April 17, 2006