Missing Peroxy Radical Sources within a Rural Forest Canopy

REFEREE 1 The manuscript “Missing peroxy radical sources within a rural forest canopy” by Wolfe et al 2014 presents a solid and unique set of measurements within a Ponderosa Pine forest. The main focus of this paper is the observation and analysis of peroxy radicals. Therefore various gas chemical measurements were utilized to run a box model and compare the modeled diel cycle to the observations. Two features of the measured diel cycle in the peroxy radical mixing ratios were standing out and difficult to represent in the model. The authors propose two different types of missing sources: One source would photolytically produce HO2, the other source generate RO2 independently of sun-driven photochemistry. The presented findings are based on observations of peroxy radicals that only recently started to become handy for field measurements. The method is known to be impacted by interferences, which were discussed in the presented study. The data has been used to assess the oxidative chemistry within a forest canopy. By comparison to the model significant mismatch has been determined and the authors extensively discuss characteristics and possible answers. The paper generally addresses interesting scientific questions related to atmospheric chemistry and the interaction between biosphere and atmosphere and is therefore suitable for publication in ACP.