Scientific Colloquium
February 15, 2017, 3:30 p.m.
Building 8 Auditorium - PLEASE NOTE CHANGE OF LOCATION
DUE TO RENOVATION OF BUILDING 3 AUDITORIUM
RALPH KAHN
GODDARD SPACE FLIGHT
CENTER
"Desert Dust, Wildfire
Smoke, Volcanic Ash, Urban and Industrial Pollution – Grasping
the Role Particles Play in Global Climate and Regional Air
Quality "
Airborne particles are
ubiquitous components of our atmosphere, originating from a
variety of natural and anthropogenic sources, exhibiting a wide
range of physical properties, and contributing in multiple ways
to regional air quality as well as regional-to-global-scale
climate. Most remain in the atmosphere for a week or less, but
can traverse oceans or continents in that time, carrying
nutrients or disease vectors in some cases. Bright aerosols
reflect sunlight, and can cool the surface; light-absorbing
particles can heat the atmosphere, suppressing cloud formation
or mediating larger-scale circulations. In most cases, particles
are required to collect water vapor as the initial step in cloud
formation, so their presence (or absence) and their hygroscopic
or hydrophilic properties can affect cloud occurrence,
structure, and ability to precipitate.
Grasping the scope and nature of aerosol environmental impacts
requires understanding microphysical-to-global-scale processes,
operating on timescales from minutes to days or longer.
Satellites are the primary source of observations on
kilometer-to-global scales. Spacecraft observations are
complemented by suborbital platforms: aircraft in situ
measurements and surface-based instrument networks that operate
on smaller spatial scales and shorter timescales. Numerical
models play a third key role in this work — providing a
synthesis of current physical understanding with the aggregate
of measurements, and allowing for some predictive capability.
This presentation will focus on what we can say about aerosol
amount and type from space. Constraining particle “type” is at
present the leading challenge for satellite aerosol remote
sensing. We will review recent advances and future prospects,
including the strengths and limitations of available approaches,
and work toward better integrating measurements with models to
create a clearer picture of aerosol environmental impacts,
globally.
About the Speaker:
Dr. Kahn, a Senior Research Scientist at NASA’s Goddard Space
Flight Center, received his PhD in applied physics from Harvard
University. He spent 20 years as a Research Scientist and Senior
Research Scientist at the Jet Propulsion Laboratory, where he
studied climate change on Earth and Mars, and also led the Earth
& Planetary Atmospheres Research Element. Kahn is Aerosol
Scientist for the NASA Earth Observing System's Multi-Angle
Imaging SpectroRadiometer (MISR) instrument, using MISR’s unique
observations, combined with other data and numerical models, to
learn about wildfire smoke, desert dust, volcano and air
pollution particles, and to apply the results to regional and
global climate-change questions. Kahn has authored about 200
technical articles, has lectured on Climate Change and
atmospheric physics at UCLA and Caltech, has presented numerous
invited talks at national and international scientific meetings,
and is editor and founder of PUMAS, the on-line journal of
science and math examples for pre-college education. He is
currently also Adjunct Professor at the University of Maryland.
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