HOx Measurements Taken During The Southern Oxidant And Aerosol Study (SOAS), 2013 Campaign And Their Implications For HOx Modeling

Open Access
- Author:
- Feiner, Philip Allen
- Graduate Program:
- Meteorology
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- November 14, 2014
- Committee Members:
- William Henry Brune, Thesis Advisor/Co-Advisor
- Keywords:
- Atmospheric Chemistry
HOx
Chemistry
Oxidation
Meteorology
Atmospheric Science - Abstract:
- OH and HO2, collectively referred to as HOx play a key role in removing many pollutants from the atmosphere. Attempts to model HOx have proven to be troublesome in forested environments with low nitrogen oxides (NOx) and high volatile organic compounds (VOCs) as model predictions rarely match measured values. It has been suggested that this discrepancy is due to unknown chemical mechanisms taking place in the atmosphere that are not being represented in chemical models. Other evidence indicates that this discrepancy is due to an interference source increasing the HOx concentrations being reported by some frequently used instruments in these low NOx/ high VOC environments. This paper examines HOx measurements from the Southern Oxidant and Aerosol Study (SOAS) and compares them to HOx concentrations predicted by the Regional Atmospheric Chemistry Mechanism Version 2, a common atmospheric chemistry model. SOAS is an environment with low NOx and high biogenic volatile organic compounds with many supporting measurements that can be used to constrain the relevant chemistry in the model. To explore the discrepancy in measured versus modeled OH in these environments, two methods for making OH measurements were used during SOAS. One of these methods is the standard way that OH has been measured in the past. The other is a newer method for measuring OH, the results of which are compared to the standard method. The results of this study imply that the model with known chemical mechanisms is able to reproduce the measured OH and that some instruments making measurements of HOx may be affected by an unknown interference signal. However, measured HO2 is twice modeled HO2 and half of the measured OH reactivity is missing. Thus, while the current mechanism and support measurements are adequate for describing OH, they are missing some important chemistry needed to describe HO2 and OH reactivity.