Research Projects

Project at a Glance

Project Status: complete

Report Published December 1983:

Title: Analysis of Santa Barbara oxidant study.

Principal Investigator / Author(s): Smith, T. B.

Contractor: Meteorology Research, Inc.

Contract Number: A2-086-32


Research Program Area: Atmospheric Processes


Abstract:

An observational study was conducted in the Santa Barbara/Ventura area in September 1980 for the purpose of developing a database for use in modeling the air quality environment in the area. The program consisted of six tracer releases together with a supporting network of surface wind stations, ozone monitors, pibal observations and aircraft measurements which supplemented the regular observational network in the area. Tracer releases were made from a number of offshore areas so that the resulting data would be of benefit in evaluating the potential impact of offshore drilling activities.

The 1980 study had as its principal purpose the generation of a data set and only cursory analyses were undertaken. The present study has utilized the data set to perform analyses related to the occurrence of high ozone concentrations in the area and the potential influence of offshore drilling.

The wind flow patterns in the channel are quite complex. Under the simplest regime in summer, the wind flow in the channel is predominantly from the west. Air parcels pass through the channel and exit up the slopes of the surrounding terrain.

At night, after the seabreeze has terminated, the air can no longer pass over the slopes due to the vertical stability gradients which develop after sunset. In this case the only routes for the eastward moving-air parcels are to be deflected to the north or south. To the south, the air can escape offshore southward along the coast. To the north, the air is deflected into a counter-clockwise eddy which does not dissipate until mid-afternoon of the next day. Slope heating and the development of the seabreeze lead to the dissipation of the eddy and a return to westerly flow.

Tracer trajectories were frequently subjected to wind shifts and light wind conditions. This led to significant dilution of the tracer material as well as uncertainties in the impact location on the coast. The maximum concentrations of the tracer as observed on the coast depended strongly on whether such wind shifts or light winds had occurred. Low dispersion (Pasquill Category E to G) was only observed when the tracer material had a direct impact on the coast under organized flow conditions. For most of the tracer tests, the maximum concentrations on the coast were reduced by the dilution associated with the light winds and wind shifts.


 

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