(BRAVO) Study: Final Report. - Desert Research Institute

Final Report — September 2004
9. EVALUATION OF SOURCE ATTRIBUTION METHODS
A variety of tests were performed to evaluate the performance of many of the
methods that were used for source attributions that are described in Chapter 10 and 11. (The
methods themselves were described in Chapter 8.) Some of the meteorological and trajectory
information that was used for those attribution analyses was also evaluated. These
evaluations are described in this chapter.
Specifically, the following evaluations and sensitivity tests were carried out:
• Meteorological model predictions were compared with routine surface
meteorological measurements, radar profiler measurements of conditions aloft,
and satellite observations of cloud fields.
• Effects of different wind fields and trajectory calculation methods on trajectory
calculations were assessed.
• Predictions of some trajectory-based methods were compared with
perfluorocarbon and sulfate measurements at the surface.
• Taking advantage of the multiple attribution methods available in the BRAVO
Study, the attribution capabilities of the Trajectory Mass Balance (TrMB) and
Forward Mass Balance Regression (FMBR) methods were evaluated using the
“artificial reality” represented by the concentration field generated by the
REMSAD model and the emissions and boundary conditions inputs into it.
• Results of simulations by both the REMSAD and CMAQ regional air quality
models were compared with surface perfluorocarbon tracer concentration
measurements at and near Big Bend National Park.
• Results of simulations by both the REMSAD and CMAQ-MADRID regional air
quality models were compared with ambient SO2 and sulfate concentration
measurements at the surface throughout the study area.
• Finally, the performance of the Synthesized REMSAD and CMAQ approaches
(described in Section 8.4.4) was evaluated by comparison with ambient sulfate
concentrations measurements throughout the study area.
These evaluation and sensitivity tests and the insights they provide concerning the
performance of the source attribution methods and their meteorological inputs are discussed
in this chapter.
9.1 Evaluation of Simulations of Meteorological Fields
The source attribution methods used in the BRAVO Study (except for TAGIT)
depend on meteorological information. All rely on wind speed and direction information,
and the regional air quality models also rely on temperature, humidity, and liquid cloud water
information. Accordingly, the first evaluations described in this chapter are for the
simulations of meteorological variables.
9-1