NASA Scientist, Dr Josh Fisher talks to HydroRisk editor, Samra Abbas about environmental research at the Jet Propulsion Laboratory

Samra: Many thanks for offering to talk to us today. Can I firstly ask you to begin by telling us a bit about what you do and how you got here?

Dr Fisher: My pleasure Samra. I work on large-scale, generally global, biogeochemical cycling with a focus on terrestrial ecosystems. In other words, how vegetation is impacted by and feeds back to climate through carbon, water and nutrient cycles. I build and run global models, putting data to models, and employing remote sensing observations to constrain and test models.

- I grew up in Los Angeles, California with my mother and Anchorage, Alaska with my father in the summers and winters, respectively. LA and Alaska were two environmental opposites: LA continuously experienced droughts, and we were installing low flow showerheads and toilets; whereas, in Alaska we were removing the low flow showerheads! All the flying back and forth, staring out of the plane window, led me to observe at length and think about a remote sensing perspective of the environment.

- I studied Environmental Sciences, which combined a lot of different sciences—biology, chemistry, physics, and so on—at UC Berkeley for both my B.S. and Ph.D. degrees, focusing on plant–water interactions, especially evapotranspiration. I built a remote sensing-based evapotranspiration model to be used in larger hydrological models. As climate change became a hot topic around the same time, it turned out that this focus became a timely and useful component to climate research as well.

- Working on global problems and questions, yet studying for nearly a decade in one place, I decided I needed to go global if I were to work global: I took up a post-doctoral research position at Oxford University in the UK. I worked primarily on two projects—the first was building a nitrogen cycle model component for the UK’s land surface model (JULES), which is the land component in the UKMO Hadley Centre climate model. I knew very little about nitrogen, having focused previously on water, but I lent my methodological approach to studying, understanding and building hydrological models to nitrogen. I spent my first year reading everything there was to know about plant–nitrogen dynamics, and built the Fixation & Uptake of Nitrogen (FUN) model in my second year (yep, I’m putting FUN into climate modeling!). The second project led me to the tropics, where I conducted a nitrogen and phosphorus fertilization experiment up and down a 3000 m elevation gradient in the Peruvian Andes and Amazon. In general, my time in the UK actually had me traveling a fair amount outside the UK, from meetings around Europe on model intercomparisons to workshops in Malaysia looking at water, religion and tourism.

- As happy as I was in Oxford, I jumped at the opportunity to return home to LA when I was offered a position at NASA’s Jet Propulsion Laboratory (JPL) at the California Institute of Technology (Caltech).

Samra: Wow – you’ve certainly had quite a journey doing lots of interesting projects and getting to visit exciting places in the process. Can we now talk a bit about where you presently work. To most, NASA is seen as a space exploration agency and it may be surprising to learn that terrestrial water research is also carried out. Please can you say why this is so.

Dr Fisher: NASA has 15 currently operating Earth observing missions ( with many more that have come and gone, and even more in development and planning. Why does NASA study the Earth? In short, you can’t understand other planets if you can’t understand your own planet. Water, especially, is central to looking for life on other planets so it is not surprising that there is a large focus on terrestrial water research at NASA.

Samra: You must have such a mass of data to enable truly cutting edge research. Can you please describe some recent water research programmes/projects that have had a lasting impact in terms of effective water management?

Dr Fisher: Perhaps one of the more politically sensitive findings was the rapid groundwater depletion in India, near the Pakistani border (Rodell et al., 2009: Nature). NASA used the GRACE satellites to detect the depletion. GRACE measures the gravitational pull of the Earth—gravity is related to mass, and when the Earth’s crust is filled with water, there is more mass; when there is less water, there is less mass. We can detect those changes in mass-related gravity that are attributable to changes in groundwater storage. These findings have also been shown in other regions on the planet where there is intense groundwater pumping. Water management strategies can use these data to manage the amount of groundwater that gets extracted.

Samra: Thank you. You’ve given an excellent example of the truly innovative research the satellite data allow. Could you please expand on your own role at JPL, which you touched upon earlier?

Dr Fisher: My particular role at JPL is to represent terrestrial ecosystems in a modeling–remote sensing context. This means that I work with specialists in other fields, such as atmospheric chemistry and circulation, ocean and ice science, and technology-focused disciplines including radar and thermal detection. I currently work on 6 projects: I) SMAP; II) CMS; III) ACOS; IV) CARVE; V) ESDR; and, VI) RTD. SMAP is the Soil Moisture Active-Passive mission ( This is a mission in development focused on measuring surface soil moisture from space that we are going to launch in just a few years. CMS is the Carbon Monitoring System ( I work on the CO2 flux component of the CMS, which combines NASA’s remote sensing-driven models in land, ocean and atmosphere, constrained by new satellite measurements of atmospheric CO2, to detect surface CO2 fluxes. ACOS is the Atmospheric CO2 Observations from Space program. My project with ACOS is similar to the CMS, but with more emphasis on using different satellite measurements of CO2 and less emphasis on linking a lot of different models together. CARVE is the Carbon in Arctic Reservoirs Vulnerability Experiment ( We are flying over Alaska and running field campaigns and models focused on CO2 and CH4 fluxes in these ecosystems that are potential “tipping points” with climate change. ESDR is the Earth System Data Records program. My project with ESDR focuses on quantifying uncertainty in different satellite-based land surface temperature observations, and how that uncertainty propagates through to models that use land surface temperature, such as models of evapotranspiration. Finally, RTD is JPL’s Research & Technology Development program. This project connects different climate elements throughout all of JPL—land, ocean, ice and atmosphere—all united through the common thread of energy and water fluxes. I am running multiple land surface and evapotranspiration models on our supercomputer as part of this project.

Samra: This extensive research will no doubt be welcome by the climate modeling community and I’m sure eventually lead to better climate models which will benefit water practitioners. I would like to ask you how working at JPL compares with working at Oxford as an academic?

Dr Fisher: I had never really considered NASA as a career—both of my parents are academics, and I saw myself staying in that direction. However, JPL in many ways offers a lot more advantages over academia. We are very collaborative, working actively with many other researchers at similar career stage levels, rather than say, working with one or two other professors in your department and with your post-docs and grad students. We have first access to satellite data—not only first access, but if we want something launched into space, we can do that! But, we need to have a strong, compelling scientific argument to have something built and launched, so we need to keep a sensitive finger on the pulse of the scientific community. Finally, there are no requirements for teaching and committees, though I do miss teaching and I can teach a little at nearby universities Caltech, UCLA or Occidental.

Samra: Is your research group expanding and how do you undertake recruitment?

Dr Fisher: My own research group currently hovers around 5 people, typically a combination of students, post-docs, programmers, consultants and visiting scholars. My group is part of a larger Water & Carbon Cycles group, which is in turn part of the larger Climate, Oceans & Solid Earth Section, which falls under the umbrella of the Science Division, and finally the Engineering & Science Directorate. JPL is pretty hierarchical, though there is a good mix of lateral/matrix organization in the structure. Typically, I’ve recruited students through my old program at Oxford University that I used to teach on, though I need to recruit and get involved with programs closer to home, such as Caltech and UCLA.

Samra: Finally Dr Fisher I wish to ask you what are some of the challenges you face in your own water-related research and how are you trying to address these?

Dr Fisher: A key challenge is getting the word out that we actually do water research, so an interview like this is great! We want people to know that we are a great resource for collaborative science projects focusing on water research.

Samra: Thanks ever so much for taking the time to speak to us Dr Fisher. You can be sure our readership will benefit from your input. Perhaps reading this will spark the interest of others to follow in your footsteps some day.

Added 19-09-11 01:13 AM

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