Peter V. Hobbs Memorial Endowed Lecture in Experimental Meteorology

Ulrike Lohmann

Professor Ulrike Lohmann

January 19, 2016

7:30-8:30, Kane Hall, Room 210

Prof. Ulrike Lohmann

Professor, Experimental Atmospheric Physics, Institute for Atmospheric and Climate Science, ETH (Swiss Federal Institute of Technology Zürich)

Lecture: "Uncertainties in Climate Prediction: The Influence of Clouds and Aerosols on Climate"



Clouds are not only fascinating to observe for their myriad of shapes, but are also scientifically challenging because their formation requires both knowledge about the large-scale meteorological environment as well as knowledge about the details of cloud droplet and ice crystal formation on the micro-scale. The ice phase in clouds remains enigmatic because ice crystal number concentrations can exceed the number concentrations of those aerosol particles acting as centers for ice crystals (so-called ice nucleating particles, INP) by orders of magnitude.

Aerosol particles can scatter and absorb radiation and with that cause a cooling, that partly offsets the greenhouse gas warming. Aerosol particles also influence the microphysics of clouds by acting as cloud condensation nuclei and INP. The magnitude and geographical distribution or the cooling caused by aerosol particles themselves and by aerosol-cloud interactions is much more uncertain than the greenhouse gas warming because aerosol particles have localized sources and sinks and only have an atmospheric residence time of days to weeks. An additional uncertainty related to clouds is that it is not yet clear how clouds change in a warmer climate. In this lecture, the progress that has been made in climate projections related to clouds and aerosols will be addressed.

About the Speaker

Ulrike Lohmann is Full Professor for Experimental Atmospheric Physics in the Institute for Atmospheric and Climate Science at ETH (Swiss Federal Institute of Technology Zürich) since October 2004.

She obtained her Ph.D. in climate modelling from the Max Planck Institute for Meteorology. Prior to her current appointment, she was an Assistant and Associate Professor at Dalhousie University in Halifax (Canada). She was awarded a Canada Research Chair in 2002, received the American Meteorological Society Henry G. Houghton Award in 2007 and was elected as a fellow of the American Geophysical Union in 2008.

Her research focuses on the role of aerosol particles and clouds in the climate system. Of specific interest are cloud microphysical processes including the formation of cloud droplets and ice crystals and the influence of aerosol particles on the radiation balance and on the hydrological cycle in the present, past and future climate. She combines laboratory work and field measurements on cloud and aerosol microphysics with the representation of them in different numerical models.

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Peter V. Hobbs Memorial Endowed Lecture in Experimental Meteorology

Paul Markowski

Professor Paul Markowski

January 23, 2014

7:30-8:30, Kane Hall, Room 220

Dr. Paul Markowski

Professor, Department of Meteorology, Pennsylvania State University

Lecture: "Storm Chasing: What I've Learned"


I will talk about my lifelong interest in tornadoes, and how fortunate I am to be able to make a living by studying them. I will discuss how our understanding of tornadoes has evolved in time and been shaped by recent field projects like the first and second Verification of the Origins of Rotation in Tornadoes Experiments (VORTEX and VORTEX2), as well as state-of-the-art computer simulations.

About the Speaker

Paul Markowski, Professor of Meteorology at Penn State University, was a leader of the recent second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2) and 2013 recipient of the National Weather Association's Fujita Award for his research on tornado formation. He has served as the Chief Editor of Weather and Forecasting since 2012.

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Peter V. Hobbs Memorial Endowed Lecture in Experimental Meteorology

Brian Toon

Professor O. Brian Toon

February 7, 2012

7:30-8:30, Kane Hall, Room 210

Dr. Owen Brian Toon

Professor, Department of Atmospheric and Oceanic Sciences, University of Colorado

Lecture: "The Anti-Greenhouse Effect Along the Spiral of Geologic Time"



Microscopic particles in the atmosphere including desert dust, sea salt, volcanic debris, air pollution and bio-particles are found everywhere on Earth. The particles nearly counterbalance the climate changes from greenhouse gases, sometimes shut down airports, and create a substantial health risk when breathed. More severe effects have occurred in the past.

For the first half of its history, Earth may have been enveloped in an organic haze, blocking the view of the surface from space, providing a UV shield and food for the biosphere. Earth nearly froze over several times, possibly triggering the origins of complex life about 600 million years ago, perhaps due to our passage through an interstellar dust cloud. About 65 million years ago particles generated from an asteroid collision in the Yucatan Peninsula broiled the dinosaurs alive, burned most of the extant land biota then froze the rest, and so diminished sunlight reaching the surface that the food chain in the oceans collapsed. In the past 100,000 years particles from giant volcanic eruptions may have nearly eliminated our species, and more recently caused migrations and stock market collapses. The future will see more events like these and possibly worse. The smoke generated in a nuclear war could kill the majority of the people on Earth. In the near future we may be forced to moderate the climate using particles to offset rising temperatures and sea levels due to greenhouse gases. If this geo-engineering to rescue our planet isn’t needed now, it eventually will be tens or hundreds of millions of years from now as the sun swells, brightens and threatens to turn our planet into an uninhabitable cinder.

Did Earth look like Titan
for half of Geologic time?
Could we all starve after a nuclear war?
Did Earth look like Titan for half of Geologic time? Could we all starve after a nuclear war?

About the Speaker

Dr. Toon is a director and professor in the Department of Atmospheric and Oceanic Sciences and a fellow at the Laboratory for Atmospheric and Space Physics at the University of Colorado. Currently, Dr. Toon is active in the following research areas: theoretical studies of stratospheric volcanic clouds and aerosols and of polar stratospheric clouds; theoretical studies of cirrus, stratus and cumulus clouds, and of direct and indirect effects of aerosols on climate; experimental investigations of stratospheric ozone loss, cirrus, stratus and stratospheric clouds, indirect effects of aerosols on clouds; and theoretical investigations of planetary atmospheres, with the goal of understanding the clouds and climates of the terrestrial planets. His research on the asteroid impact that killed the dinosaurs led to the discovery of nuclear winter due to the major decrease in temperature. He is a fellow of the American Meteorological Society and the American Geophysical Union.

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Peter V. Hobbs Memorial Endowed Lecture in Experimental Meteorology

Greg McFarquhar

Professor Greg McFarquhar

May 21, 2010

3:30-4:50, Johnson Hall, Room 075

Dr. Greg M. McFarquhar

Professor, Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign

Lecture: "Use of In-situ Observations to Examine Aerosol Impacts on Mixed-Phase Arctic Clouds, Radiation and Climate"



Comprehensive data on arctic boundary layer aerosol and cloud microphysical and radiative properties were collected during the 2004 Mixed-Phase Arctic Cloud Experiment (M-PACE) and the 2008 Indirect and Semi-Direct Aerosol Campaign (ISDAC). During M-PACE, data from in-situ microphysical sensors were collected that characterize how cloud particle shape, size, phase and bulk properties varied with height. A much more comprehensive dataset was obtained during ISDAC, in which an unprecedented suite of 42 cloud and aerosol instruments was employed to study the influence of aerosols on clouds affected by ice. In-situ data obtained during ISDAC above, below, and within single-layer stratus are leading to a process-oriented understanding of how aerosols affect the microphysical and radiative properties of arctic clouds. Ultimately these data will be used to improve the representation of cloud and aerosol processes in models covering a variety of spatial andd temporal scales, and to determine the extent to which long-term surface-based measurements can provide retrievals of aerosols, clouds, precipitation, and radiative heating in the Arctic.

About the Speaker

Dr. McFarquhar is a leading authority on Cloud Physics, especially the physics of ice particles in clouds. In the tradition of Peter Hobbs, McFarquhar has led many field experiments using aircraft to make detailed measurements in clouds. His scholarship and teaching have been honored by the University of Illinois and the Canadian Meteorological and Oceanographic Society.

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Peter V. Hobbs Memorial Endowed Lecture in Experimental Meteorology

Keith Browning

Sir Keith A. Browning

Friday, October 24, 2008

Inaugural Lecture

Dr. Keith A. Browning

FRS, Emeritus Professor, University of Reading

Lecture: "Origins of the Most Damaging Winds in Extra-Tropical Cyclones"


About the Speaker

Dr. Browning served as the Director of Research in the UK Met Office. He is a Fellow of the American Meteorological Society, receiving the Rossby Medal in 2003, Past President of the Royal Meteorological Society, receiving the Symons Gold Medal in 2001, and a Fellow of the Royal Society. His work with Frank Ludlam on the supercell thunderstorm at Wokingham, UK in 1962 was the first detailed study of such a storm. His research covered many areas of mesoscale meteorology including developing the theory of the Sting jet.

Post-Lecture Reception

Reception Image

Inaugural reception on October 24, 2008, at Kane Hall.
Stephen Hobbs (left), Ann and Keith Browning, Sylvia Hobbs (right).
Photo: D. Hartmann

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