Charlie was a force at the GFD program, sitting in left rear and giving insightful questions and comments to all. His lectures were superb, and his enthusiasm was ---well, like the football photo; top notch! His interest in upper bounding theory brought the entire field back up after its early blossoming in the 1960-70 era and I could not have been more happy to see him work on this forever, but not to be. Carry on, all you bounders!

Charlie was one of a kind. He was a role model who impacted the life and career of many of us. Through working with him as a GFD fellow, I learned how to find upper bounds (and play softball). In the next few years after that, I also learned from Charlie how to be a better collaborator, better colleague, and better person. Charlie truly enjoyed what he worked on, and he made it enjoyable for everyone else too. The GFD program and DFD/SIAM meetings will not be the same without him. Charlie will be sorely missed.

Charlie's work is amazing. Simple, elegant, and mathematically deep all at the same time. His work has served as an inspiration for me. He was always an energetic and prominent figure at conferences. He was friendly, and made a concerted effort to reach out and support junior people (myself included). Not only were his talks were clear and insightful, but they had this unique "Doering" humor that always made them memorable. He will be missed!

I had the privilege of having a final exchange with Charlie two weeks ago. I send my original message, and then his reply, showing that from his youth he knew the Bible better than most of us.
On Sat, May 1, 2021 at 1:23 PM Robert Kerr wrote:

There is a time for everything,
  and a season for every activity under the heavens:
  a time to be born and a time to die,
  a time to plant and a time to uproot,
  a time to kill and a time to heal,
  a time to tear down and a time to build,
  a time to weep and a time to laugh,
  a time to mourn and a time to dance,

And at this time we have had too much of the dying and mourning.
For those of left with tasks of surviving and rebuilding, I hope
it ends soon.

And for you, I thank the friendship and knowledge you have
given me and others over the years. It will not be forgotten.

Bob Kerr

Thank you, Bob.

Your words – and Ecclesiastes' – mean a lot to me.

---Charlie.

Charlie Doering was friend to many, a mentor to a lucky group of students, postdocs and younger colleagues, and a treasured colleague across many disciplines. Charlie leaves an amazing legacy of scientific excellence, professional integrity, and personal warmth and charm. He had a profound influence on the Center for Nonlinear Studies, first as an eager and productive postdoc, then and later as a frequent visitor, and for an all too brief time as the CNLS Deputy Director where he served as a steady hand during uncertain times. Even after leaving CNLS for the University of Michigan, Charlie always held CNLS in high regard, attending many conferences and visiting often; his latest CNLS Colloquium was in December 2020. His boundless energy and enthusiasm, his scientific acumen, and his wisdom and charm will be missed by many. We keep in our thoughts his family and friends during this difficult time.

Charlie was a great scientist with a plethora of accomplishments, and he taught me so many things. Perhaps the greatest lesson he taught me was in the way he lived. For Charlie, the scientist and the person always mattered more than the science itself. His priorities were always shaped by the life circumstances of his many collaborators and their needs. I hope that I can continue his legacy of doing quality science, and at the same time prioritize the people involved in that science.