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Researcher Feature: Atmospheric physicist Brian Carroll provides insights on the NASA Postdoctoral P

Brian inside the cockpit of a NASA aircraft on a science mission.

Brian onboard the NASA P-3 aircraft as an in-flight science lead. This campaign flew over and through marine clouds, collecting data to advance synergies of state-of-the-art remote sensing instruments.


My name is Brian Carroll, and I’m an atmospheric physicist. My research focuses on lidar remote sensing algorithms and analysis, applied to studies ranging from moisture transport and cloud processes to wildfires and air quality. After earning a PhD in atmospheric physics, I spent two years as a NASA Postdoctoral Program (NPP) fellow at NASA Langley Research Center. The NPP is a program that spans all NASA centers and disciplines with unique opportunities to receive directed funding for 1-3 years of research. My postdoc concluded in the summer of 2022 and I recently took a Research Scientist position at NOAA in Boulder, Colorado through a contract with the Cooperative Institute for Research in Environmental Sciences.

  1. Can you briefly tell us about your trajectory into research?

I became interested in research as a natural progression of what drew me into physics in the first place: I enjoy problem solving and expanding our understanding of the earth system, and humanity’s place in it. Atmospheric physics stood out to me more so than more “pure” physics fields because the connections from the classroom to everyday personal experiences were so apparent. My first research opportunity was in my department at the University of Maryland, Baltimore County (UMBC) and involved local air quality studies along with wind energy research for the Maryland area. Taking ozone and aerosol data that pretty directly affected local warnings and policies was fulfilling – and I got to go outside! At that time in my life, just learning how to manipulate and visualize observational datasets with all of their unique features and limitations was a pretty big challenge for me. Regardless, this launched my ongoing research career, and contacts that I made through that position helped me get to where I am today.

I chose to do a postdoc after my PhD because I wasn’t sure yet what direction I wanted my career to go. A postdoc could lead to a career with the same group, but in general it was a great opportunity to further develop my skill set and network while narrowing down my preferred options for a full-time position.

  1. Can you describe the application process for a NASA Postdoctoral Program fellowship from start to finish?

I knew I was interested in government lab research after my PhD, and since there are multiple NASA research groups in my field I started searching for opportunities on the NPP website. I reached out about a few posted opportunities, directly contacting the listed advisor for each to discuss in greater detail what their current research and group direction is, and what they’d expect from an NPP fellow. NPP funding comes externally, so the advisor does not need to provide the NPP stipend. This makes an NPP fellow a great benefit to any group, and advisors are often willing to discuss and find what research path fits best for the candidate rather than needing to fulfill a very specific research grant objective. I had a discussion with my NPP advisor about how my goals could fit within the current needs of the group. I started the application process early so that I could get feedback on the main research proposal document from my advisor, ensuring that it fit within the scope of the group and aligning my objectives with NASA mission statements.

Note that AGU H3S and CUAHSI hosted a webinar on October 20 on applying to postdoctoral fellowships at US SCience Agencies including NASA. The recording will be made available here.

  1. What did you study as an NPP fellow?

My NPP research was centered around a state-of-the-art lidar system that profiles water vapor and aerosol properties from aircraft (the High-Altitude Lidar Observatory, HALO, which also has capability for ocean and cloud measurements). My tasks ranged from data processing algorithm development to scientific analysis, with particular focus on addressing how moisture and aerosols in the atmospheric boundary layer affect cloud processes connecting to global circulations and climate. I also got to participate in a large field campaign based out of the Caribbean, which was a great experience. Multiple universities and NASA centers participated, along with international collaboration. We spent 3-4 days per week flying in the NASA DC-8 over the Atlantic, taking data while enjoying incredible cloud formations and sunsets over the open ocean.

Working with the measurements all the way through processing and eventual scientific analysis offers a great perspective with positive feedback, from nuances of the measurement affecting scientific interpretation back to what new observations could best address science questions. My NPP unfortunately began shortly after the start of the pandemic, so the new remote work modality heavily affected my ability to interact and learn from the research group. But beyond the myriad stressors and limitations of the time, everyone was very welcoming and happy to help me learn and get integrated with the group.

  1. How did your NPP experience differ than being a PhD student?

The biggest difference between my PhD and NPP experiences was the research environment. Performing research with a group at a NASA research center was vastly different from my relatively small graduate program. I was very independent and did fairly unique research within my graduate program. In my NPP I was much more integrated as a member of a larger team, though still with enough independence to pursue my personal research interests. Interacting with the decades of world-class expertise within my group at NASA was an invaluable experience, along with learning first-hand how a research group functions within the NASA government lab framework.

  1. How did the NPP influence where you are today?

My time as an NPP fellow benefited me in many ways that made me a more capable and informed researcher. The NPP did not directly lead to my current position at NOAA, but I gained expertise in my field and broadened my network. I also gained valuable perspective being in a government lab research environment (as opposed to academia or industry), which helped in deciding my next steps. Beyond the research, seeing the outreach impact that NASA has not just in the U.S. but around the world was inspiring. There is a lot of work to be done in balancing the prosperity of both people and the planet, but a lot of us are already together on that path with hearts in the right place.

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