The Scripps Institution of Oceanography Marine Observatory: A Platform for Real-Time Measurements of the Coastal Ocean and Atmosphere

The Scripps Institution of Oceanography Marine Observatory (SIOMO)was established in late 1997 as a facility for the study of coastal ocean and atmospheric processes. The observatory consists of two 10-m diameter discus buoys, the first moored 3.5 miles off Point La Jolla near Scripps the second located 5 miles west of San Clemente Island. Interior laboratory space houses control and logging computers. Power is supplied by a 24-volt battery bank; recharging is carried out automatically by a diesel generator that can also be used to supply direct power to instrumentation if required. Sufficient fuel is stored to allow untended operation for periods of up to 1 year.

The buoys are equipped to measure basic state meteorological variables - temperature, pressure, humidity, and wind speed and direction - along with water temperature. Additional instrumentation includes an ADCP for the measurement of ocean current profiles, and a laser ceilometer to determine cloud base height or boundary layer depth. Instrumentation may be located on a central 8-m tower, or any of three 10-m towers located around the periphery of the buoy. Tracks on the 10-m towers enable sensors to be moved between 2 and 10-m above the surface. Two airfoils maintain one side of the buoy into wind; the orientation and attitude of the buoy are monitored via GPS. Most variables are sampled as 1-minute averages, and the data transmitted to shore via spread-spectrum radio frequency modem. Real-time data are made available through a web page (http://tenby.ucsd.edu) along with historical time series and an archive of hourly averaged data for the entire period of operation.

A primary research focus of these platforms is the study of air-sea interaction. To this end turbulence instrumentation is being installed to enable the measurement of direct eddy correlation fluxes. Collocated measurements of the surface wave field and radiative fluxes will complete the assessment of the surface energy budget. The large volume of data and wide range of conditions sampled by a long-term facility such as the SIOMO will enable comprehensive studies of surface exchange processes in a manner not possible from short-term deployments.

The use of the observatory facilities and data by other researchers is encouraged. The data logging system is extensible, allowing additional instrumentation to be addedeasily. The SIOMO provides the research community with platforms for the study of a wide variety of physical, chemical, and biological processes and for the testing of new instrumentation and techniques. Recent studies have included an evaluation of the use of GPS signals to measure atmospheric water vapor from moored platforms, an investigation of infrared propagation in the marine atmospheric surface layer, and the calibration of wind measurements from free drifting buoys. The real-time meteorological and oceanographic data is also used for operational purposes by the US Navy, commercial and sport fishermen, and local yachtsmen.