The San Joaquin Valley Air Quality Study
This is a partial reconstruction of the original project report.
Dry deposition is an important sink for pollutants and consequently it plays an important role in the formulation of the lower boundary condition in photochemical and pollution transport models. Because dry deposition is important for modeling purposes, the California Air Resources Board sponsored a large field program in July and August of 1991 to study the dry deposition of ozone in the San Joaquin Valley. This field experiment,called the California Ozone Deposition Experiment (CODE) is part of the larger San Joaquin Valley Air Quality Study. CODE was designed to provide information on the nature of the physical and biological processes governing the dry deposition of ozone in the San Joaquin Valley and for developing and evaluating air quality models for that region.
Synopsis of Field Phase
The San Joaquin Valley Air Quality Study (SJVAQS) ASTER deployment was sponsored by the California Air Resources Board of the state of California to quantify the ozone deposition flux to crop vegetation and served to produce imput data for the air quality models used for regulatory purposes. Bill Massman and Larry Marht were the principal investigators and Jim Pederson was the contact manager for the CARB. Tony Delany was the ASTER scientist and Steve Semmer the ASTER engineer. Tom Horst, Steve Oncley, and Charlie Martin were involved in the ASTER research. In addition to the ASTER cotton field investigation two other ground based surface flux facilities were deployed; the Environment Canada facility (Gerry den Hartog) in a raisin grape vinyard, and the University of California at Davis (Roger Shaw) in a dry grass field. The Environment Canada instrumented Twin Otter aircraft (Ian McPherson) overflew all sites. Sonoma Tech, a consulting firm, was responsible for site preparation. Prior to the field phase a planning meeting was held at the office of the CARB in Sacramento. Tony Delany attended and made preliminary arrangements as to site requirements. The general location of the research site was determined by Ian McPherson and Paul Hanson of Sonoma Tech. Tom Horst and Steve Semmer made a site visit to check the micrometeorological validity of the site and the logistics for the deployment. The truck containing the field-ware and the single ASTER seatainer arrived at the site June 25th, 1991 and the walk-ways, towers, power and data cabling was laid out. Some postponement was involved due to a delay in the installation of the power drop. The sensor installation was completed by July 7th, and the system was operational on July 11th. A rental trailer required for the PG and E monitors, the suppies for the pilot balloon system operated by Fresno State College, and the contents of the ASTER second seatainer was positioned south of the ASTER seatainer. The NOAA WPL mini-sodar was south of the PG and E trailer. Operations were continuous from July 11th to August 7th (JD 192 - JD 219), 1991. Tear-down and repacking of the trailers occupied a four day period. The ASTER site was located 80 km west of Fresno in the central valley of California. Maps 1 and 2 show the location of the site relative to urban areas and the major highways. Maps 3 and 4 illustrate that the facilty was situated in an extremely open flat agricultural area of cotton, tomatoes, melons, and beans with very few obstructions and with access roads and irrigation canals on the section or quarter section boundaries. A skyline survey indicates the scacity of nearby obstructions. The tower array was erected 150 m from the eastern edge of a cotton field. The site plan illustrates the relative positioning of the five towers, the radiation array, the instrument shelters and the access walkways. Of particular note is the exhaust for the fast ozone sensor vacuum pump. Under the prevailing meteorological conditions the NOX laced exhaust was emitted down-wind of the ASTER array and sufficiently cross-wind from the PG and E that it was not sensed. However during quiescent nighttime conditions the exhaust spread across the site and represented a problem. The site plan and the sensor configuration diagram show the arrangement of the meteorological, chemical, and radiation instruments. The soil temperature and heat flux sensors were located near the dark-horse, the 4m stand upon which the radiation sensors were mounted. The soil sensors were distributed such that both ridge and furrow were represented. Samples were taken each day from both ridge and furrow to measure the gravitational soil moisture.
Near Firebaugh, California (36 deg 48' 50"N, 120 deg 40' 38"W).
A table of sensors is available.
Daily weather plots were included in the original project report, but are not currently online.
The 5-minute average statistics in NetCDF format are available here.
A compendium of various formulae and constants is available.