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EXPERIMENTAL AND THEORETICAL EVALUATIONS OF OBSERVATIONAL-BASED TECHNIQUES
Impact/Purpose:
The objective of this task is to critically evaluate the theoretical foundations of current OBMs and then test predictions from these OBMs against experimental data. The experimental measurements will verify whether or not they are correct in their predictions of the sensitivity of ozone formation to NOx or VOC emissions reductions. We will examine the robustness of a variety of OBM indicators (such as O3/NOy, H2O2/HNO3, etc.) over various types of ambient conditions. Once we have uncovered a set of reliable OBM formulations, we will pass this information to follow on tasks which compare these validated OBMs against predictions from EBMs, such as Models3.
Description:
Observational Based Methods (OBMs) can be used by EPA and the States to develop reliable ozone controls approaches. OBMs use actual measured concentrations of ozone, its precursors, and other indicators to determine the most appropriate strategy for ozone control. The usual approach for developing control strategies is to use complex Emissions Based Models (EBMs), such as Models3, to prescribe ozone control scenarios for future years. OBMs give us an alternative method for characterizing ozone formation, as well as a way to evaluate and verify the predictions of EBMs.
One drawback to using OBMs is that we have no proof that the predictions made using OBMs to determine ozone sensitivity to emissions controls are correct or reliable. Current OBMs have only been tested against model predictions, but since most OBMs are derived from model simulations, this is not an independent test of their validity and will not tell you if the OBMs themselves are correct or not. In order to perform a truly independent verification of the OBMs, this task will test the formulations and predictions of several OBMs that predict ozone sensitivity against experimental measurements of ozone formation and sensitivity to emissions reductions. Initial experiments will be done in a carefully controlled smog chamber environment at conditions that mimic NOx and VOC reductions in the atmosphere, and that optimize the differences between VOC and NOx sensitivity. Later experiments will be done in ambient atmospheres to extend the conclusions into "real" atmospheres. OBMs that pass the validity tests in these studies will be studied in more detail in related tasks.