Faculty Profile: Dara Entekhabi
Bacardi and Stockholm Water Foundations Professor CEE and Department of Earth, Atmospheric and Planetary Sciences
By Rebecca Gianotti S.M. ’08, Ph.D. ’13
Civil & Environmental Engineering Correspondent
After completing his Ph.D. in 1990 with Professor Emeritus Peter Eagleson, Dara Entekhabi spent a year on the faculty of the University of Arizona before joining the MIT faculty in 1991. His research spans a range of topics in hydrology and hydrometeorology, including land-atmosphere interactions, surface water-groundwater interactions, data assimilation and remote sensing. He is director of MIT’s Earth System Initiative, served as director of Parsons Laboratory from 2006 to 2013, and gave the American Meteorological Society’s Horton Lecture last year. Entekhabi is the science team leader for NASA’s Soil Moisture Active and Passive (SMAP) satellite mission, scheduled to launch Nov. 5, 2014.
You’ve been working on the SMAP mission since 1999. That’s a long time to be dedicated to one project!
Entekhabi: Yes, but it’s also rewarding. It’s going to be a whole new perspective for the water cycle, with data that will allow a quantum leap in our understanding of how the Earth system works. It’s exciting to see it finally come together.
What new information will come from SMAP?
Entekhabi: The main science contribution is that it globally maps soil moisture, which is the variable that links the major cycles of the Earth system: the water, energy and carbon cycles. Right now there are no global in situ networks to measure soil moisture. There are some regionalized networks — some point measurements here and there — but really you cannot infer what the global soil moisture field variations are from these networks. If you’re going to do Earth system modeling and global modeling for weather or climate applications, you need global soil moisture at the highest resolution possible.
Are there any unique aspects of this mission?
Entekhabi: This NASA mission is unique in that the data will be used directly by other federal, state and local agencies in real time. For example, the National Weather Service produces daily flash flood guidance based on precipitation and temperature data used in empirical models. Wherever the falling precipitation exceeds the estimated soil moisture deficit, operators issue a flash flood warning. SMAP will provide exactly what they need: direct observations of soil moisture at an order of magnitude higher resolution than is currently available.
Also, we recently started to work with a network of schools in NASA’s GLOBE program for education and public outreach. The gold standard for soil moisture measurement calibration is the gravimetric measurement. Students can make this measurement using a tin can, a kitchen scale and an oven. It’s very labor intensive, but any school can do it. They will make measurements and upload the data to the web in real time. The data will be used in the calibration of SMAP, and in return we will give them a stream of satellite data carved out for their location. So they will actually be part of the mission validation in a substantive way.
What aspect have you worked on most recently?
Entekhabi: I’ve been in charge of the main data product, the activepassive algorithm. With colleagues at the Jet Propulsion Laboratory, my students and I developed an algorithm and tested it against heritage airborne experiment data and against simulated data. We had an airborne field experiment last summer through Canadian partnerships, which was specifically designed to test this algorithm.
Has it been challenging to coordinate work across multiple universities and research agencies?
Entekhabi: Yes, but the leadership teams at JPL and Goddard Space Flight Center and I have been working together since 1999. We’ve worked together for so long that we think almost alike and we can interchange our roles and represent each other. We trust each other implicitly, and we’re basically one person in three different locations.
Would you ever consider going into space yourself?
Entekhabi: I would. Having been through the experience of seeing SMAP designed, blueprinted, produced and tested, I know that the amount of care and diligence that goes into creating a satellite system is incredible. There’s no getting your million-dollar experiment back from space to fix something, so it has to work the first time. So I can just imagine that the standards for human space flight must be unbelievable. And it would be great fun. You know that first Earthrise photograph [taken on the Apollo 8 mission]? That was a transformative image for all of us; we have this planet that’s enclosed, the one and only, and we can’t go experimenting with it without thought. To see the Earthrise in person would be quite an experience.