STAMPS Seminar - Jonathan Lilly
December 5, 2025 1:30PM—2:30PM
Location:
Virtual Presentation - ET
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Remote Access - Zoom
Speaker:
JONATHAN M. LILLY,
Senior Scientist, Planetary Science Institute
https://www.psi.edu/staff/profile/jonathan-lilly/
The problem of mapping scattered data is considered from the perspective of the earth sciences. A particularly promising method is local polynomial fitting, which involves fitting not only a field of interest, but also its derivatives up to some specified order, in the vicinity of each grid point. Among other desirable properties, this method has the virtues of simplicity and ease of application. Local polynomial fitting is adapted for use on the sphere by recasting it in terms of the coordinates of a local tangent plane. Three algorithmic choices lead to substantially improved maps. Firstly, the use of a variable bandwidth, in which the smoothing radius is not constant but varies to incorporate a fixed number of data points, performs well with irregularly spaced data. Secondly, first- and second-order fits are shown to offer considerably improved performance compared with a zeroth-order fit due to a property known as design adaptivity. Third, a generalized kernel is introduced that subsumes existing forms in the literature and which allows a wider degree of possibilities. With these considerations, the problem of mapping sea surface height from alongtrack satellite measurements—an important data analysis problem in oceanography—is considered. Applying the method to a numerical model, for which errors can be assessed directly, a sweep through parameter space is conducted to identify optimal parameters. The results are compared with the community standard product, and sources of remaining error are discussed.
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Jonathan M. Lilly was born in Lansing, Michigan, in 1972. He received the B.S. degree in atmospheric and oceanic physics from Yale University, New Haven, Connecticut in 1994, and the M.S. and Ph.D. degrees in physical oceanography from the University of Washington in Seattle, Washington, in 1997 and 2002, respectively. From 2003 to 2005 he was a postdoctoral researcher in the Laboratoire d'Océanographie Dynamique et de Climatologie, Université Pierre et Marie Curie, Paris, France. Since 2005 he has worked as a research scientist or senior research scientist at various institutes, including Earth and Space Research, NorthWest Research Associates, and Theiss Research. Since July 2021 he has been a Senior Scientist at the Planetary Science Institute in Tucson, Arizona, and since June 2024 he has been a visiting scientist in the Department of Physics at the University of Toronto in Toronto, Canada. Since September 2025 he is also serving half-time as Lead Oceanographer for Oceanbox AS in Tromsø, Norway. His research interests include oceanic vortex structures, statistical methods for data analysis, Lagrangian observations, and high-latitude oceanography.
Zoom Participation. See announcement.
For More Information:
tsukiant@andrew.cmu.edu