AUTHOR RESPONSE TO LETTER TO THE EDITOR

摘要

Dear Editor, We are pleased to respond to B. Rappenglueck and G. Lubertino's comments on our paper (Wormhoudt et al., 2015). However, before responding to their specific comments we want to emphasize that we regard Wormhoudt et al. as an extension of Rappenglueck et al. (2013), not a rejection of their work. They present fleet average emission factors for several important on-road vehicle exhaust species. We realized that during the same field campaign we had collected additional data in other Houston sectors that could be compared to their results. Our results also extend the range of exhaust species measured. We think our publication illustrates that fleet emissions are dependent on fleet composition and traffic conditions, which can and do differ in various sectors in a city as large as Houston. We believe the results in each publication should be used to refine and improve on-road emission models for Houston, by providing data that better describe the variability of exhaust emission factors. We proceed to offer some clarifications, followed by a few comments.