Recognition for pioneering work
Professor leads the way in satellite oceanography

Oceanographer Xiao-Hai Yan, co-director of the Center for Remote Sensing in the College of Marine Studies (CMS), has been appointed the Mary A.S. Lighthipe Professor of Marine Studies in recognition of his research, teaching and service to the University.

In announcing the honor, UD President David Roselle and Provost Dan Rich cited Yan’s “notable record as a scholar and educator.”

Since he joined the UD faculty in 1990, Yan has pioneered the use of satellites in tracking a range of ocean and coastal phenomena, from El Niño to oil spills.

In 1992, he was the first scientist to show that satellite images, in addition to actual temperatures of the sea surface, could be used to precisely determine the size and location of the Western Pacific Warm Pool. That pool is a body of water the size of Africa, spanning the equator from the western Pacific to the Indian Ocean. It holds the warmest seawater in the world.

Fluctuations in the warm pool’s temperature have been linked to the onset of El Niño and other large-scale climate events. Yan’s results were published by the American Geophysical Union and by Science magazine, as well as a variety of U.S. and international news media, and have become a classic reference in climate studies.

Recently, Yan discovered that the warm, choppy waters generated in the Pacific Ocean by El Niño cause a slight imbalance in the Earth’s rotation that may slightly extend the length of the day. He and other members of a nine-person research team analyzed satellite maps and found a correlation between elevated temperatures in the Western Pacific Warm Pool during years with strong El Niño currents and a tiny extension in the length of day. The researchers examined 30 years of water temperature data, from 1970-2000. Their study is the first to link the behavior of a large water mass to the rotation of the planet.

This coupling between the ocean and the atmosphere and its effect on the solid Earth was selected by the American Geophysical Union as one of the most significant scientific findings made in 2002.

Yan currently is pushing the field of satellite oceanography beyond its traditional boundary at the ocean’s surface. He has developed a new data-processing method that now enables researchers to “break through” the waves and detect what’s below them.

The new tool can determine the depth of the ocean’s mixed layer—the area that wind affects, typically ranging from 25 meters (82 feet) to 200 meters (654 feet) beneath the surface. Knowing the mixed layer’s depth is important to marine biologists studying the growth of microscopic algae and to climatologists working on computer models of the global climate system.

Yan and postdoctoral researcher Young-Heon Jo recently used the new method to locate elusive currents called “Meddies” that occur at depths of more than a half-mile, flowing out of the Mediterranean Sea into the Atlantic Ocean at the Strait of Gibraltar. These warm, salty Mediterranean currents are difficult to track because they sink beneath the cooler waters of the incoming Atlantic.

In other studies using a combination of light, heat and radar-energy data gathered by satellites orbiting hundreds of miles above the Earth, Yan has developed new techniques for monitoring and predicting the pathways of oil spills, the movement of ice and other oceanic features. He also has provided global climate researchers with a new method for rapidly measuring the difference between the temperature of the ocean and the temperature of the air, a critical factor in determining the Earth’s heat balance.

Yan’s research has been funded by the U.S. Office of Naval Research, NASA, the National Science Foundation, the Jet Propulsion Laboratory, the National Oceanic and Atmospheric Administration and Delaware Sea Grant.

He has published more than 200 scientific journal articles and research reports, is associate editor of the Journal of Remote Sensing and serves on the editorial board of the Journal of Oceanic and Coastal Sea Research.

In addition to maintaining an active research program and helping to oversee the operation of UD’s Center for Remote Sensing, which received a NASA Center of Excellence Award in 1997, Yan teaches several graduate courses. He has advised 27 graduate students, 10 undergraduate students and six postdoctoral researchers.

Among his honors, Yan received the prestigious Presidential Faculty Fellow Award in 1994. The award is presented annually by the president of the United States to 30 exceptionally promising scholars early in their academic careers.

He also received the honorary Cheung Kong Chaired Professorship at the Ocean University of China in 2000. Sponsored by the Li Ka Shing Foundation of Hong Kong and the Ministry of Education in China, the permanent chair is awarded to only a few scientists throughout the world. In October, Yan was the keynote speaker at the institution’s 80th anniversary celebration.

Yan received his bachelor’s degree in marine science from Tong Chi University in Shanghai, his master’s degree in remote sensing physics from the Shanghai Institute of Technical Physics, Academia Sinica, and his doctorate in satellite and physical oceanography from the State University of New York.

This is the second chaired professorship made possible by the endowment of the late Mary A.S. Lighthipe. A.D. Kirwan Jr., director of the Physical Ocean Science and Engineering Program at the College, received the honor in 2000.

A native of Sussex County, Del., Ms. Lighthipe had a longtime interest in the state’s Inland Bays and the research and teaching of the College of Marine Studies.

— Tracey Bryant