Dr. Judith Lean Elected to AGU Fellowship

4/8/2002 - 18-02r
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Dr. Judith Lean, of the Naval Research Laboratory's (NRL's) Space Science Division has been elected a Fellow of the American Geophysical Union (AGU). Fellowship in the AGU is an honor conferred upon scientists who, in the eyes of the AGU, have "attained acknowledged eminence in the geophysical sciences."

Dr. Lean has worked in NRL's Space Science Division since 1986, where her research focuses on the mechanisms, measurements and modeling of variations in the Sun's radiative output at all wavelengths, and the effects of this variability on the Earth's global climate and space weather. She is a guest investigator on NASA's Upper Atmosphere Research Satellite (UARS), Living with a Star (LWS) and Sun-Earth Connection (SEC) programs, and a co-investigator on the Solar Radiation and Climate (SOURCE) and Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) space missions.

Dr. Lean and her coworkers provided the first quantitative study of the relative roles of sunspots and other smaller, more numerous solar features in controlling the solar constant over short (27-day) and long (11-year) solar cycles. Their studies completely reversed earlier theories drawn primarily from sunspot data and moved the science of sun/climate connections from speculative belief to one grounded in physical understanding and solid data.

Dr. Lean's research into the distribution by wavelength of electromagnetic radiation, which produces the Sun's total brightness output, is considered by colleagues to be a breakthrough discovery. Dr. Lean showed that, while emissions from the ultraviolet portion of the spectrum account for only one percent of the Sun's total brightness, they actually affect the variations in total brightness that occur as the Sun's activity waxes and wanes by about 20 percent.

Because the ultraviolet radiation from the Sun is the primary source of energy for the Earth's atmosphere, this finding of the disproportionately large role of the UV spectrum in solar brightness variations prompted a series of studies that investigated how ultraviolet light modulates the upper and lower atmosphere. Subsequent coupling within the Earth's atmosphere suggested a mechanism for amplifying solar effects on climate over alternative proposed mechanisms based on less physical models.

Dr. Lean is a recognized expert on the Sun's role in global climate change and has testified before the US Senate Committee on Energy and Natural Resources on the Science of Climate Change and the US Senate Committee on Commerce, Science and Transportation Subcommittee on Science, Technology and Space on this topic.

Dr. Lean received a B.Sc. (Hons), Physics in 1974 from the Australian National University, Australia, where she was awarded the Priscilla Fairfield Bok Prize as the university's best female student in the field of science. In 1980, she received a Ph.D. in atmospheric physics in 1980 from the University of Adelaide, Australia.

Dr. Lean is a member of the American Geophysical Union, the International Association of Geomagnetism and Aeronomy, the American Astronomical Society-Solar Physics Division, and the American Meteorological Society. She currently serves as a member of the National Research Council's Board on Atmospheric Science and Climate and the National Science Foundation's (NSF's) Advisory Committee for Geosciences, and has previously served on numerous panels and advisory groups for NASA, NRC and NSF.

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