Central California Ozone Study (CCOS) - Desert Research Institute

CCOS Field Operations Plan Version 2: 5/31/00
aircraft include two Cessna 182 operated by University of California, Davis (UCD), and a Cessa
182 and Piper Aztec operated by Sonoma Technology, Inc. (STI). These aircraft will provide
information at the boundaries and will document the vertical gradients, the mixed layer depth,
and nature of elevated pollutant layers throughout the CCOS modeling domain. The
concentrations and (in conjunction with upper air wind soundings) the transport of pollutants
across selected vertical planes will be measured to document transport of pollutants and
precursors between offshore and onshore and between air basins.
In addition, the U.S. Department of Energy Gulfstream 159 (G-1) will participate in
CCOS during a two-week period from 6/28/00 to 7/12/00 through the Atmospheric Chemistry
Program (ACP). This collaborative effort is headed by Pacific Northwest National Laboratory
(PNNL) with contributions from Argonne and Brookhaven National Laboratories. The issues of
interest for the ACP investigation are formation of elevated ozone layers and their impact on
surface concentration, differences in chemical processing between the elevated and mixed layers,
and time-evolution of the chemical partitioning between chemically active and stable species.
Other questions of secondary interest are the effects of local thermally driven circulation on the
introduction of emissions into the mixed layer, chemical processes in up/down valley or slope
flows, and the influence of advection of air into the Central Valley on the distribution of
pollutants within the Valley. The G-1 will also characterize the boundary conditions along the
western boundary of the CCOS modeling domain.
One additional aircraft (Twin Otter), flown by the Tennessee Valley Authority (TVA),
will make measurements in power plant plumes. These data will be used to evaluate the plumein-grid
(PiG) parameterizations used in air quality models. The plume study is described in
Addendix D of the CCOS Field Study Plan (Fujita et al., 1999).
2.6.1 Overview of Flight Plans
Alternate flight plans have been developed for the two UCD and two STI aircraft
corresponding to the type of ozone episode that is forecast for the IOP day. The three types of
ozone episodes are described in Section 3 and are summarized here.
Type 1 - The San Francisco Bay Area (SFBA) has its highest basin-wide ozone values,
though still less in absolute magnitude than San Joaquin Valley. This scenario is characterized by
the weakest sea breeze (lowest west-to-east component through Carquinez Strait), and the lowest
Oakland inversion base heights.
Type 2 - The San Joaquin Valley (SJV) has its highest basin-wide values while the Bay
Area and Sacramento Valley are relatively cleaner. A stronger sea breeze, relatively to Type 1,
keeps the pollutants moving through the Bay Area and the Sacramento Valley, but may increase
transport into the SJV. Mountain Counties have lower ozone levels during this scenario.
Type 3 – Sacramento Valley (SV) has its highest basin-wide ozone values, as does the
Mountain Counties Air Basin. As with Type 2, a stronger sea breeze is present, relative to Type
1, but the daily maximum surface temperatures in Sacramento Valley are significantly higher,
indicating less and/or later intrusion of the sea breeze, allowing more time for photochemistry
before evening transport to the Mountain Counties.
Chapter 2: FIELD MEASUREMENTS 2-46