scope:

EXECUTIVE SUMMARY

During the Fall of 1985, the American Petroleum Institute sponsored a field tracer study near Carpinteria, California (75 miles northwest of Los Angeles) to develop a data base for evaluating air quality models applicable to offshore and coastal emission sources. In particular, the data collection effort focused on those parameters that are important to the new Offshore and Coastal Dispersion Model developed by the Minerals Management Service. The study was also designed to provide information that would allow researchers to evaluate model performance in situations involving complex terrain or fumigation conditions. The contractor for the field studies was WESTEC Services, Inc. of San Diego, California. Principal Investigator was Dr. Timothy C. Spangler of Northern Illinois University.

A total of 13 case study data sets were assembled during the period from September 19 through October 5, with the first eight experiments conducted in an area of complex terrain. The last five cases were carried out during fumigation periods in a nearby area with flatter terrain.

Meteorological data were collected at an onshore tower and consisted of horizontal wind direction and wind speed measurements, U-V-W wind component measurements, temperature data, and calculations of sigma phi and sigma theta values. In addition, one-second wind direction values were recorded during each case to provide a raw data base that may also be used to calculate sigma theta values during the experiments.

Offshore meteorological conditions were measured from Platform Hazel located 3 miles west of Carpinteria and from a boat anchored near the Carpinteria Pier. Platform measurements consisted of wind speed, wind direction, U-V-W wind components, temperature data, and air-sea temperature difference values. Meteorological data collected from the boat were taken using a tethersonde system flown from a large balloon. Wind speed, wind direction, dry bulb and wet bulb temperatures and pressure readings were taken from this system at various altitudes. Sigma theta data were also calculated from the tethersonde wind directions.

Pollutant plumes from a hypothetical offshore source were simulated using sulfur hexafluoride and Freon 13B1 tracers released from tubes held aloft by a large balloon. This balloon was anchored on a second boat located near the Carpinteria Pier. The tracer gas was collected in one-hour integrated samples (half-hour samples for the fumigation cases) that were obtained at approximately 40 locations. These samples were then analyzed by gas chromatogrpahy to provide a spatial and temporal picture of plume transport and impact in the area.

Additional plume and meteorological measurements were provided by instrument packages mounted on a helicopter. An onboard, continuous SF6 analyzer provided information on the position and-width of the tracer plume. Temperature sounding data from the helicopter were also collected several times each day,

Since the purpose of the field study was to develop a data base to be used in future research efforts, this report contains a detailed description of the data set and F the circumstances of its acquisition, rather than extensive analyses- of the data. Volume I summarizes the data collection, with listings of the data provided in Volume II. A magnetic tape containing complete project data listings is also available.