My research group combines numerical modeling (deterministic, stochastic) and/or analytic solutions with small and large-scale measurement (direct and indirect observations), and inverse modeling (parameter estimation, data assimilation, model averaging, etc.) to improve theory, understanding and predictability of complex Earth systems. We engage in all aspects of the iterative research cycle (see figure below) and regularly develop new numerical, computational, statistical, and optimization approaches to reconcile complex system models with observations for the purpose of learning and scientific discovery and, thereby, enhancing the growth of environmental knowledge. We use distributed computing to permit inference of CPU-intensive forward models.
Our papers appear in a wide variety of different scientific journals, and describe methodological advances, and their application to problem solving in (alphabetic order) agriculture, avian biology, ecohydrology, ecology, fluid mechanics, geomorphology, groundwater, hydrogeophysics, hydrogeology, geophysics, geostatistics, surface hydrology, soil physics, vadose zone hydrology, and water resources.
Our current methodological work focuses on, (i) a new paradigm of process-based model evaluation (to help diagnose which components of the model are malfunctioning), (ii) likelihood-free inference (use of summary metrics in geophysics as a powerful and “objective” alternative to the rather “subjective” deterministic penalized least-squares inversions), (iii) Bayesian model selection (inference of marginal likelihood through multi-dimensional integration of the posterior distribution), (iv) emulation of CPU-intensive models (to permit inference of computationally demanding models), and (v) monitoring network design (real-time measurement selection to help discriminate among conceptual models).
More application oriented work includes (amongst others), (a) investigation of the environmental controls of photosynthetic capacity (ecology), (b) global-scale hydrologic modeling (hydrology), (c) uncertainty quantification of GEOS-5- L-Band radiative transfer parameters (remote sensing), (d) joint inference of multi-Gaussian permeability fields and their geostatistical properties (hydrogeology), (e) the biogeography and composition (particulate ratios) of marine plankton (ecology), (f) two- and three-dimensional subsurface characterization (geophysics), (g) scaling and prediction of soil hydraulic parameters (soil physics), and (h) geomorphological modeling of soil depths (geomorphology / sediment transport). Publications on these different topics are forthcoming.
We share freely all our work with others, and provide short-courses for those interested in numerical modeling and model-data analysis.
2006 – 2009: J. Robert Oppenheimer Distinguished Postdoctoral Fellow, LANL, USA
2005 – 2006: Directors Funded Postdoctoral Fellow, LANL, USA
2000 – 2004: PhD in Science, University of Amsterdam, Netherlands
1994-1999: MS in Physical Geography, University of Amsterdam, Netherlands
Main Lecturer for a week long short-course on “Bayesian inverse modeling and data assimilation methods in the Earth Sciences“. Once or twice a year, at a different University worldwide. Look for more information under “Teaching / Outreach”
2008 – present: Vadose Zone Journal
2009 – present: Environmental Modeling & Software
2008 – 2015: Hydrology and Earth Systems Sciences
2010 – 2015: Water Resources Research
Other Professional Activities
2004 – present: Chair and Organizer of 30+ sessions at (inter)National conferences
2004 – present: About 80 invited talks and seminars at Universities, Inter(National) Meetings, and Labs.