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Winter 2000

NCAR Interactions

by Paul Crutzen

Editor's note: The last in our series of distinguished NCAR collaborators, Paul J. Crutzen, was director of the Atmospheric Chemistry Department of the Max Planck Institute for Chemistry in Mainz, Germany, from 1980 till last July. He has also held part-time teaching positions at the University of Chicago, Scripps Institution of Oceanography, and Utrecht University. His main scientific interests are global modeling of chemical processes from the troposphere through the lower mesophere and the role of atmospheric chemistry in climate and biogeochemical cycles. In 1995, Crutzen received the Nobel Prize in Chemistry 1995 with Mario Molina and Sherwood Rowland.

Paul Crutzen.

In 1974, after my graduate studies at the University of Stockholm and postdoctoral studies at Oxford and Stockholm, I joined the Upper Atmosphere Project of NCAR, headed by John Gille, on a half-time appointment (the other half being spent as a consultant at the Aeronomy Laboratory of NOAA in Boulder). These early times were a highly exciting period in atmospheric chemistry.

In 1970 and 1971, my own work and that of Harold Johnston of the University of California, Berkeley, showed that nitric oxide (NO) and nitrogen dioxide (NO2) could catalyze ozone destruction in the stratosphere. This work developed into a highly political and international issue after it became known that the large fleets of supersonic aircraft that were planned in the United States, Great Britain/France, and the Soviet Union would inject about as much NO in the stratosphere as is naturally produced by the oxidation of nitrous oxide (N2O). This realization became the start of major research programs in the United States, France, and Great Britain. The research efforts were further accelerated after Mario Molina and Sherwood Rowland's 1974 research proposing that stratospheric ozone could be significantly depleted by the release of chlorofluorocarbons in the atmosphere.

NCAR made major inputs to these research programs through

The modeling efforts were ably supported by the computer facilities of NCAR, first on a CDC, later on much more powerful machines that now enable the running of fully coupled, three-dimensional chemical transport models. In the early days we worked with punch cards in big boxes. I still remember with great fear the way the computer operators would pick up all the cards from a half-meter-long box, pushing against both ends of the stack with the palms of their hands, and then would load them in the program reader. With very few exceptions things went right, but it was better to pray for the best and not to watch.

The balloon experiments normally took place at NCAR's balloon facilities at Palestine, Texas, and the flight programs were carried out on the Sabreliner jet aircraft, ably handled by the Research Aviation Facility of NCAR.

My involvement with NCAR and NSF became particularly intense after I accepted the offer by NCAR director Francis Bretherton to become director of what was then called the Atmospheric Quality Division (AQD), later renamed the Atmospheric Chemistry Division (ACD).

AQD's research did not remain restricted to the stratosphere, but increasingly included studies on tropospheric ozone and the catalytic role of nitrogen oxides (NOx) in ozone production in the troposphere and lower stratosphere. This research was largely carried out with Jack Fishman and Lou Gidel with funding by the Environmental Protection Agency to Colorado State University. I remember so well how difficult it was convincing the EPA that NOx should be at least as important as hydrocarbons in the production of ozone under photochemical smog conditions.

Through our work at NCAR we also showed that ozone on large scales was substantially influenced by the catalytic action of NOx with ubiquitous methane and carbon monoxide serving as the atmospheric combustion fuels. On regional scales, the emissions of hydrocarbons from vegetation are also of great importance. We foresaw the great potential importance of emissions from vegetation. This was the start of a major research program within ACD, initially led by Pat Zimmerman.

During my last years at NCAR before I returned to Europe in 1980, some exciting new efforts started. One was the Monsoon Experiment, led by Joachim Kuettner. In MONEX, Tony Delany piggybacked with ozone measurements, in which he profited very much from the collaboration with the meteorologists. This small project was followed by the Global Atmospheric Measurements Experiment on Tropospheric Aerosols and Gases, the first dedicated air chemistry program, led by Doug Davis of the Georgia Institute of Technology with active participation of ACD.

Also during my final years at NCAR, we got strongly involved with a new issue: the effect of tropical biomass burning on global atmospheric chemistry. During two observational programs over the savannas and forests of Brazil, we could demonstrate the great importance of this nonindustrial kind of air pollution. The research team involved, besides myself, Tony Delany, Pat Zimmerman, Leroy Heidt, Rich Lueb, Walt Pollack, Bill Mankin, Mike Coffey, Jim Greenberg, Art Wartburg, and Phil Haagensen.

My relatively brief period at NCAR was indeed very rewarding, and I am grateful for all the support I received. I know that the same high- quality support for research is available nowadays. It was abundantly shown during the multiagency and highly international INDOEX intensive field campaign that was carried out in the Indian Ocean region during the dry monsoon months of early 1999 with V. Ramanathan of Scripps Institution of Oceanography as the "spiritual leader." I thank the many people of the NCAR technical facilities and the UCAR Joint Office for Science Support who made possible this major field experiment. INDOEX has produced highly significant results, showing the great regional influence of the air pollution created on the Indian subcontinent and Southeast Asia on the composition of the atmosphere on the Indian Ocean region during the dry season north of the intertropical convergence zone. Some 70 papers will result from the program. It was a great pleasure for me and some of my co-workers to be the guest of NCAR's Climate and Global Dynamics Division. We collaborated with Phil Rasch and Bill Collins to implement the models for the interpretation of the INDOEX chemistry data.

It is impossible to mention all who contributed to the great success of INDOEX, but I will make one exception: Joachim Kuettner, who has remained an inspiration for almost half a century.


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Edited by Carol Rasmussen, carolr@ucar.edu
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Last revised: Wed Feb 7 15:34:33 MST 2001