+ Earth Observing System > Who's Who > EOS Project Scientists > Robert F. Cahalan

EOS Project Scientists

Dr. Robert F. Cahalan

Code 613.2
Goddard Space Flight Center
National Aeronautics and Space Administration
Greenbelt, MD 20771
USA

Phone: (301) 614-5390
Fax: (301) 614-5493
Email:robert.f.cahalan@nasa.gov

Dr. Robert Cahalan is Head of the Climate and Radiation Branch at NASA/Goddard, which he joined in 1979, coming from NCAR in Boulder CO. He is also Visiting Senior Research Scientist at ESSIC, Adjunct Professor of Physics at UMBC, PI of THOR lidar, chair of the 3DRT Working Group of the International Radiation Commission, NASA Project Scientist for the EOS SORCE mission that launched in January 2003, Project Scientist of the International Intercomparison of 3D Radiation Codes (I3RC), and NASA representative to USGCRP/CCRI. He is a member of the DoE ARM Science Team, and the NASA EOS-Landsat Science Team. Dr. Cahalan has been a graduate advisor at universities in the USA, Canada, and the Netherlands, and Visiting Scientist at NCAR, Aspen Center for Physics, Institute of Theoretical Physics in Warsaw, and ECMWF in Reading, England. Dr. Cahalan's research focuses on climate and cloud structure, developing retrieval techniques that extend the "independent pixel approximation" (IPA) by use of 3D transfer methods, and parameterizations such as the "effective thickness approximation" (ETA) that relate cloud optical properties to cloud structure. Dr Cahalan led development of a new measurement approach "Thickness from Offbeam Returns", realized in Goddard's innovative THOR lidar system that combines a multiple field-of-view wide-angle receiver with 3D retrieval methods to determine the thickness of optically thick cloud layers. THOR is now being adapted to measure thickness of snow and sea ice layers. Dr. Cahalan directs the Intercomparison of 3D Radiative Codes (I3RC) that has developed a set of benchmarks used to certify 3D radiative transfer codes, and is now coordinating a community 3D coding effort.

Dr. Cahalan has also studied predictability and chaos in simple climate models, beginning with a paper on fluctuation-dissipation in stochastic energy balance models, followed by one on the diffusive "cloud dot" model, and a paper with G. North on a stochastically forced "doubly decoupled" diffusive energy balance model. In 1990 he published a paper with his son Gabriel on "Chaotic rhythms of a dripping faucet" which uses a simple quadratic Henon model to predict chaotic intervals between successive drips of a leaky faucet for a certain range of mean drip rates, and shows successive attractor bifurcations as drip rates increase, as well as intermittency and apparent intransitivity at certain fixed drip rates. Dr. Cahalan enjoys using the "climate" of a leaky faucet to motivate discussions of the richer complexity of the climate of Earth.