Dr. Nystuen investigates ocean surface processes that affect the underwater sound field. He has developed a technique to use the underwater sound field to detect and monitor rainfall at sea. This technique is presently being adapted for use on deep ocean moorings and remote satellite-linked ocean drifters in order to make climatic observations of rainfall patterns over the oceans. His Passive Aquatic Listeners (PALs) also provide long-term detection and quantification of sound-producing biological and anthropogenic activities in the ocean. These data provide a unique acoustical description of ocean climate. Results of his research have appeared in the Journal of the Acoustical Society of America, the Journal of Atmospheric and Oceanic Technology, and other scientific publications. Dr. Nystuen joined APL in 1995.