Azadeh Tabazadeh

2001 James B. Macelwane Medal Winner

NASA Ames Research Center

Azadeh Tabazadeh received the Macelwane Medal at the 2001 Fall Meeting Honors Ceremony on 12 December, in San Francisco, California. The medal is given for significant contributions to the geophysical sciences by young scientists of outstanding ability.


“It is my great pleasure to join in recognizing Dr. Azadeh Tabazadeh’s talent, accomplishments, and promise as memorialized in the Macelwane Medal. Azadeh is noted for her many applications of physical chemistry to problems of importance in atmospheric science. She is an inspiring young scientist, willing to help others as shown by her wide collaborations in the community, but also very forceful in presenting her own ideas.

“Dr. Tabazadeh first came to the atmospheric science community’s attention through her graduate work at UCLA with Howard Reiss and Rich Turco. She initially explored the role of volcanic eruptions in injecting chlorine compounds into the stratosphere. Volcanic gases are rich in chlorine, which if it all reached the stratosphere would overwhelm the anthropogenic contributions of chlorine to the stratosphere. Therefore, reductions in anthropogenic chlorine emissions such as occurred in the Montreal Protocol would have been fruitless. Azadeh showed that the chlorine would be removed by precipitation in the moist rising volcanic column before it could enter the stratosphere. This paper ended twenty years of debate about this subject through its thorough analysis and plausibility.

“Azadeh then turned her attention to polar stratospheric clouds, the agent responsible for the formation of the Antarctic ozone hole. These clouds were originally thought to be composed of solid hydrates of nitric acid. However, observations seemed to be inconsistent with such hydrates. She examined the physical chemistry of sulfuric acid/nitric acid/water mixtures and showed that ternary liquid solutions could exist in the stratosphere. This paper, as well as independent studies by others, paved the way to understanding the behavior of a large fraction of these clouds. Such understanding has been one critical factor in the ability of the science community to convince policy makers that loss of ozone in the polar regions was understood, and that regulations of harmful chemicals could be justified.

“I was fortunate to collaborate with Azadeh after she moved to NASA’s Ames Research Center in 1994. She is now a member of the research staff at Ames. Azadeh was the recipient of a Presidential Early Career Award for Scientists and Engineers in 1998, which resulted in a visit to the White House. During the past several years, Azadeh played a significant role in a number of analyses of satellite data that shed further light on the properties of polar stratospheric clouds and their impact on stratospheric chemistry. For example, her work with Michelle Santee challenged views widely held in the stratospheric chemistry community concerning the mechanisms by which nitric acid is removed from the stratosphere. Such denitrification is a critical component in predicting the loss of ozone in the stratosphere during the next hundred years. Azadeh showed the importance of denitrification to continued and expanded ozone loss in the Arctic as greenhouse cooling lowers stratospheric temperatures. She provided the first physical-chemical theory of how large particles nucleate which allows a quantitative examination of the denitrification process. She has also inspired and challenged a number of laboratory studies of aerosol physical chemistry, which has helped in the rapid expansion of this area of research.

“Dr. Tabazadeh’s work has not been limited to the stratosphere. She has made important contributions to understanding the formation of ice in the upper troposphere, a critical issue in cirrus cloud formation. In addition, she has investigated the removal of nitric acid from the upper troposphere by its interactions with clouds and with mineral or organic aerosols. These papers are important contributions both to atmospheric chemistry and cloud physics.

“Azadeh has made major contributions to geophysics already in her career. She is energetic, willing to challenge accepted dogmas, and daring enough to overturn them. Moreover, she is an unselfish collaborator who is already working with a broad array of other scientists to help them with their studies. For these reasons, Azadeh is deserving of recognition through the Macelwane medal.”

—OWEN B. TOON, Atmospheric and Oceanic Science Program, University of Colorado, Boulder


“Thank you very much, Brian, for your overly generous citation. I know that I am standing here tonight because a distinguished group of scientists decided that I deserve to receive this honor.

“It has been a privilege for me to work and collaborate with Brian Toon, a former NASA senior research scientist. Brian is not only a brilliant scientist, but he is also a very kind person with a gentle and encouraging personality. His character along with the depth of his scientific knowledge made it possible for me to start trusting myself early on in my career. Jack Kaye, the director of Earth Science Research Program at NASA headquarters, has been a true supporter of my work since my early days in graduate school. When you are as young as I was and some high-profile program director at NASA believes in your work, then you too will start believing in yourself. I am also grateful to Estelle Condon, my boss, for working so hard to make sure that our efforts at NASA Ames are recognized and appreciated by the scientific community. Overall, this medal truly belongs to NASA for continuously encouraging and supporting my work over the last decade.

“I also thank my husband, Mark, for his love and support and our children, Dionna and Daniel, for bringing so much joy into our lives. Dionna once asked me, ‘What do you do at your work?’ I told her, ‘I am a scientist.’ She asked, ‘What is that?’ I told her, ‘I study the clouds, rainbows, and many other interesting things that you often like to paint.’ She said, ‘Well, I also like to paint dinosaurs, and I don’t think I want to be a scientist. I want to be a bone collector when I am all grown up.’ Luckily, what she meant was to take all her friends to a desert (and not a cemetery) to dig for dinosaur bones. She also tried hard to convince me not to worry too much about those clouds because they are always there in the sky for everyone to see, whereas dinosaur bones are hiding in the sand waiting for ‘little’ people (like her) to find them. At last I told her, ‘If you work really hard, you will be the most famous grown-up bone collector on the Earth.’ In fact, as a little girl my favorite toy was a rare chemistry kit that my uncle Mahmoud brought back from Germany when I was about 7. I use to put the white coat and goggles on and pretend that I was a famous magician who was able to make anything, despite the fact that my little sister Afshan became hysterical whenever she saw me as a magician. My mother accidentally broke the goggles (beyond repair) after a few days. Later, my father’s reading glasses replaced the goggles, and he had to constantly wipe my fingerprints off his glasses. However, he let me get away with it because he knew that I really wanted to play this game, and my little sister was also very excited to see me wear his glasses. Ironically, that fictitious magician is a real chemist today, and our daughter too can transform a bone collector into a paleontologist if she sets her mind to it. So if you happen to know a little girl who has big dreams, make sure she knows that what she wants or pretends to be today can be her tomorrow when she is all grown up.

“Last but not least, I sincerely thank my parents for giving me a second chance in life. Nineteen years ago, a couple of years after the Islamic revolution in Iran, it was just a dream for a young woman to even think of pursing a career in science. In 1982, they left their aging parents (whom they never saw again), their relatives, their friends, and the life they built together for almost 20 years so that my siblings and I could have at least a decent chance in life in the United States. It is because of their unselfish sacrifices that I am living today the life of my dreams.

“In closing, I feel extremely fortunate for being able to share my thoughts with many magnificent colleagues and my life with a wonderful family. Who could ask for anything more!

“I thank the AGU for this great honor, and I thank all of you for your attention.”

—AZADEH TABAZADEH, NASA Ames Research Center, Moffett Field, Calif.