the San Joaquin Valley Air Quality Study (SJVAQS)

The major goal of the San Joaquin Valley Air Quality Study (SJVAQS) and the Atmospheric Utility Signatures, Predictions and Experiments (AUSPEX) field study was to provide air quality, meteorology, and emissions data necessary to develop the capability to model the effect of emissions changes on air quality. One of the principal elements of the study was the measurement of thermodynamic properties and winds aloft. Some objectives of the upper-air meteorological measurements were to:
· provide meteorological fields that can be used to initialize, bound, and otherwise optimize the output of prognostic meteorological models used to predict wind, temperature, humidity, and mixing height throughout the study domain;
· provide a field of observations that can be used as input to diagnostic meteorological models that will interpolate available data in light of terrain interaction and thermal influence; .
· provide a field of observations that can be used to evaluate the performance of the prognostic and diagnostic wind models; and
· provide a field of observations that can be used to study specific meteorological phenomena which have been identified in earlier studies.
The San Joaquin Valleywide Air Pollution Study Agency contracted with T&B Systems to set up, maintain, and collect data for an upper-air balloon soundings network of 15 fixed locations within the San Joaquin Valley. T&B Systems also was responsible for processing data collected at a sixteenth site, Angels Camp, which was operated by Pacific Gas & Electric (PG&E).
A unique aspect of this study was the necessity to utilize several different methods of wind measuring; navaid, radio-tracking, and optical tracking. This requirement was necessitated by a number of factors. Since as many as 20 sondes could be telemetering data simultaneously (NOAA and the NWS were providing soundings as well), it was necessary to utilize equipment that transmitted at varying frequencies. Moreover, as it turned out, there was no single manufacturer that could provide the number of sondes required within the project timeframe. T&B Systems therefore acquired navaid-based sounding systems, radio-theodolite sounding systems, and crystal-controlled transmitting sondes that required optical tracking for winds. We set up a training program for over 30 student-operators and developed standard operating procedures.
The field study took place from July 2 to August 23, 1990. Within this time period, on days when the regional ozone was predicted to exceed state and federal standards, all the elements of the program collected data in a coordinated effort. There were a total of 14 intensive sampling days. A team of meteorologists forecast candidate intensive sampling days, and the decision to operate on a candidate day was made by the SJVAQS/ AUSPEX management team.
On intensive sampling days, up to eight soundings daily were taken at each site based on a schedule specific to the requirements of each site. A total of 1,439 soundings were 1,439 soundings were taken on 14 intensive days.

In the process of developing a validated data base, T&B Systems personnel subjected the field measurements to quality assurance tests that included a number of data review steps. Upper-air data taken by PG&E personnel at Angels Camp were merged into the T&B Systems data base and underwent the same quality assurance and review procedures whenever possible. A data report containing a summary table of observations taken, plots of each sounding, and computer files of the data were submitted separately at an earlier date.