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in-cites,
September 2006
Citing URL: http://www.in-cites.com/scientists/BarryJHuebert.html
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An
interview with:
Professor Barry J. Huebert |
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 his
month, in-cites talks with Dr. Barry Huebert about his highly
cited work in the field of Geosciences. Dr. Huebert’s work
was singled out by Essential
Science Indicators
as having the highest percent increase in total citations in
July 2006. His current record in Geosciences includes 36
papers cited a total of 851 times to date. Dr. Huebert is a
Professor in the Department of Oceanography at the University
of Hawai’i at Manoa.
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Would you give us a little
background on your education and early research?
I earned my BA in Chemistry from Occidental College in 1967 and
my PhD in Physical Chemistry from Northwestern University in 1970.
In about 1976, while teaching at Colorado College, I began to get
involved with atmospheric chemistry research as a participant in the
Global Atmospheric Measurement Experiment on Tropospheric Aerosols
and Gases, GAMETAG. We flew from the Beaufort Sea to south of New
Zealand sampling the relatively unpolluted portions of the
atmosphere. That got me hooked on airborne research: you get to play
with airplanes and instruments, you get to see the world, and you
get to characterize parts of the Earth no one has taken these
instruments to before. Talk about fun work!
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“It’s hard to imagine a tougher problem than organic aerosols: there are literally thousands of compounds, most at such low concentrations that you couldn’t measure them well even if you could identify them all.”
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As my own research program has developed, we have concentrated on
improving measurement methods. Many instruments are deployed without
enough thought to possible errors and artifacts, unfortunately.
Perhaps the best examples are the inlet tubes used to bring
atmospheric particles into airplanes for collection and study. We
determined that the commonly used inlets actually removed many
particles, so instruments never got samples that accurately
represented the atmosphere. Two decades and many dollars later, we
now have a Low-Turbulence Inlet (LTI) that allows us to understand
how the sample in the airplane compares with the ambient air outside
the plane.
We have used relatively low-tech methods (filter and impactor
collection) to bring particles back to our lab for analysis of the
major anions and cations by ion chromatography. By doing these very
carefully, we have been able to see diurnal variations in some
species and vertical gradients in others, so that we could establish
formation and loss rates for them. We also developed a Lagrangian
method for making observations, in which repeated aircraft flights
visit the same, tagged airmass to measure how various substances
evolve with time. Such experiments involve many people and
platforms, so they cannot be done very often.
Several of your papers deal with the ACE-Asia project. Would
you talk a little about this project – how did it get started, what
have some of the findings been and what are their implications, and
what is the project’s current status?
The Asian Aerosol Characterization Experiment was developed by
the International Global Atmospheric Chemistry Program, IGAC, of
which I was a part. We recognized the importance of understanding
the nature of the dust and pollution particles exported from Asia,
particularly in the springtime westerlies. These particles provide
essential iron to the Central Pacific fisheries, but also bring
unwanted pollutants to regions downwind. (Similar experiments have
been done recently looking at North American outflow.) Scientists
from the East Asian region and elsewhere worked jointly to plan this
program, which had an intensive field observation period in the
spring of 2001.
Fortunately, we violated the First Law of Field Programs, (whatever
you are trying to observe won’t be there when you take a lot of
people and platforms to study it) because 2001 was a very dusty
spring. One of our dust storms was tracked by satellites all the way
from Western China, across North America, to the Canary Islands in
the Eastern Atlantic. We learned a lot about how natural and
pollution particles interact, often by mixing to produce a very
different kind of particle. Acidic pollutants, for instance, can
make mineral dust more soluble, freeing up some of its iron to serve
as an ocean nutrient. We also gathered a huge data set of the impact
these particles have on sunlight, so it is being widely used for
testing climate models. The project itself is finished and special
journal issues have been published, but our openly archived data
will be used for decades to come.
What about the GOCART and ASTEX/MAGE experiments – were the
findings there similar to those from ACE-Asia? (Or is this trying to
compare apples and oranges?)
Goddard Chemistry Aerosol Radiation and Transport
(GOCART) wasn’t an
experiment, but a chemical transport model developed by Dr. Mian
Chin at NASA Goddard Space Flight Center. It was one of the models
used to forecast plume tracks for flight planning during ACE-Asia.
The Atlantic Stratocumulus Transition Experiment/Marine Aerosol
Gas Exchange (ASTEX/MAGE)
was a precursor to ACE-Asia, in a way. In this case, the experiment
was initiated by a group of scientists interested in the properties
of stratocumulus clouds and the dynamics of the air in which they
are found. The aerosol/chemistry experiment was added on by IGAC as
a way to help these atmospheric physicists study the impact of
aerosols on clouds (currently called the indirect effect on
climate). We did our first successful Lagrangian experiment in ASTEX/MAGE,
tracking an airmass for two days.
As always, one finds more questions than answers in the field, so
this led into the series of ACE experiments. ACE-1 took place south
of Tasmania to study the clean background atmosphere, and ACE-2 took
place in European outflow. In each case we were looking at very
different particle regimes, dominated in one case by dust, in
another by sea salt, and in the third by urban/industrial air
pollution. Each broadened our understanding of the variability of
the atmosphere.
Your June 2006 Atmospheric Chemistry and Physics paper
sums up the advances and current state of organic aerosols. What major
advances have been made, and what still needs to be done with regard
to these chemicals in the atmosphere?
It’s hard to imagine a tougher problem than organic aerosols:
there are literally thousands of compounds, most at such low
concentrations that you couldn’t measure them well even if you
could identify them all. Furthermore, many of these substances are
volatile, so sampling artifacts make it nearly impossible to collect
a representative sample. Finally, many of them continue to be
oxidized with time, becoming more soluble in water and therefore
changing their impacts on clouds and light scattering. The
analytical challenges are tremendous, but progress is being made.
Our ACP paper outlines the challenges and suggests ways to
move forward. Organic aerosols are like an iceberg: 90% of it hasn’t
been seen or understood yet.
If you are free to discuss it, please tell us about your
current work.
We have several exciting things underway. Chief among them are
measurements of the flux (rate of exchange) of biogenic
dimethylsulfide (DMS) gas from the ocean to the atmosphere. By using
technology recently developed at Drexel University, we have been
able to measure this flux more rapidly and accurately than has been
possible for almost any gas. The result is that we are learning
things about many factors that control gas exchange, but which could
not previously be probed for lack of a measurement method that could
see flux changes on the same time scales as wind, bubbles, waves,
surfactants, and the many other likely controlling factors. We are
working on a similar method for measuring the important CO2 flux,
which could have a very large impact on our modeling of climate.
We are also involved in planning the VOCALS experiment, which
will be similar to ASTEX/MAGE but with vastly more sophisticated
instruments and in the Southeast Pacific off Peru and Chile. This
region experiences large, sudden openings in the usually dense low
clouds, which has a huge effect on the capture of solar radiation
(and thus on climate). Models do a lousy job there, so we are going
in with ships and aircraft to look at the ways that aerosols and
clouds affect one another, with many of the same PIs as ASTEX/MAGE.
Finally, we have begun a long-term program to study organic
aerosols in the free troposphere. The few measurements during field
campaigns don’t give any picture of seasonal changes, so we have
placed an OA sampler at the Mauna Loa Observatory where we collect
samples each night. We have already seen that during the spring
Asian outflow, the OA concentrations peak. It’s neat how all these
projects derive from and lead back to one another.
Barry Huebert, PhD
Department of Oceanography
University of Hawai’i at Manoa
Honolulu, HI, USA
| Professor Barry J. Huebert's
most-cited paper with 155 cites to date: |
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Chadwick OA,
et al., "Changing sources of nutrients during four million years of ecosystem development,"
Nature 397(6719): 491-7, 11 February 1999. |
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Source:
Essential Science Indicators |
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in-cites, September 2006
Citing URL: http://www.in-cites.com/scientists/BarryJHuebert.html
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