Boulder, CO. The international capital of atmospheric research?

International collaboration is a cornerstone of modern science. This is why funding agencies generally make mobility an important part of any funding application. Academy of Finland is not different and my Academy Research Fellow project includes several instances of mobility. As I was preparing my proposal including ozone reactivity measurements, I was made aware of the unpublished work from Prof. Detlev Helmig and his team on this topic at the Atmospheric Research Laboratory (ARL), part of the Institute for Arctic and Alpine Research (INSTAAR) at the University of Colorado in Boulder. After contacting Prof. Helmig, he agreed to host a laboratory visit in order for me to get familiar with their method. As the project got funded, the visit was settled for the beginning of 2018.

Therefore, after visiting Prof. Matsumoto in Tokyo, I embarked on another trip, this time to the United States of America, and this time together with Anssi. I stayed for three weeks there in January to discuss various aspects of ozone reactivity measurements and atmospheric chemistry research as well as to help getting everything started. Anssi will remain additional four weeks to continue laboratory experiments and acquire additional knowledge that he will bring back to Finland for our project.

While I was there we set up and characterized the ARL's system for ozone reactivity measurements with the invaluable help of Jacques Hueber and Dr. Wei Wang's input. Among other things, we learned (or were reminded) of:

• the importance of conditioning tubing before any test or experiment,
• how to run a commercial ozone monitor in "differential mode",
• pressure drops,
• patience, and
• the existence of imperial units.

For atmospheric scientists, Boulder has been known for a long time as a research hot spot with agencies such as the National Oceanic and Atmospheric Administration (NOAA), the National Center for Atmospheric Research (NCAR) and the University of Colorado. In this perspective, it is a vibrant place to do this kind of research.

Figure 1. Boulder viewed from the Flatirons (top). Flatirons seen from the East Campus of the University of Colorado (bottom). (Pictures: Arnaud Praplan, CC-BY-4.0)

Detlev gave a talk on 23 January at NCAR Foothills Laboratory on the impacts of U.S. Oil and Natural Gas Development in a packed auditorium. He showcased both the local work of his team at the Boulder Reservoir as well as its international involvement and expertise on volatile organic compounds measurements.

During our free time, we explored Boulder's downtown, went on a hike to the Flatirons, and tried several restaurants and pubs. Detlev invited us, colleagues, and alumni from his laboratory (with significant others) to his house for a delicious dinner, during which we had a chance to show a few slides about ourselves and talk about Finland. We also went to Happy Hour after work to enjoy the local craft beers! I also caught up with fellow atmospheric scientists Ale, Christina, and Aga!

Now I am back in Helsinki and I'll continue to plan our future measurements while learning more from Anssi as he continues to experiment with ozone reactivity. At the same time I'll work on OH reactivity data from the last years. Stay tuned!

Figure 2. Top row (from left to right): Entrance of CU Research Park; Quote on the pavement at the entrance of CU Research Park; Boulder Creek. Bottow row (from left to right): "Be Boulder" sticker at CU; SEEC Building on East Campus (INSTAAR location); wildlife on CU East Campus. (Pictures: Arnaud Praplan, CC-BY-4.0)