Trinidad Head Observatory (THD) is located on a point jutting into the ocean along the remote northern coast of California approximately 40 km (25 miles) north of Eureka, California, the main regional population center. The coastal climate is dominated by maritime influences, with moderate year-round temperatures and moderate-to-high humidity. To the immediate west of Trinidad Head is the unobstructed Pacific Ocean and to the east are redwood dominated forest lands. The town of Trinidad represents the primary community in the immediate vicinity and supports approximately 400 year-round residents. The Telonicher Marine Laboratory (TML), a satellite facility of Humboldt State University (HSU), is also located in Trinidad.
Because of the characteristics of a relatively remote coastal location (insignificant anthropogenic influences and prevailing maritime airflow) the Trinidad Head site is an important location, providing and opportunity to observe and monitor both regional and global influences. An instrument trailer was installed in April 2002 allowing measurements of aerosols, surface ozone, radiation, and flask sampling for halocarbons and carbon cycle gases. Bi-weekly airborne vertical profile measurements will provide a continuous baseline of pollution and climate forcing agents in air entering the U.S. Further plans include installing a GCMS for measuring PAN, hydrocarbons, and certain halocarbons. Additional measurements will be included as the Observatory matures. Already, at this location, Scripps Institution of Oceanography is operating two in situ instruments, one as part of the Advanced Global Atmospheric Gases Experiment (AGAGE), the other for measuring changes in atmospheric oxygen concentrations.