I have two major concerns on this manuscript and encourage the authors to elaborate more about the points below.
1. The major concern, as both reviewers address, is the instrumental or sampling biases due to the missing inter-comparison and horizontal separation in their set-up, during the mission. I do understand the limitations in real mission, so I suggest the authors to conduct more lab tests to address the relative TE (transmission efficiency) dependence of two instruments on various meteorological parameters; repeat figure 1 type experiments for different parameters such as temperature, pressure and RH to verify the possible biases in instruments in quantitative way. (The ionization efficiency may vary with that kinds of parameters.)
2. If the measurements were conducted within the roughness sublayer, point measurement likely have limitations in inferring larger scale exchange (Raupach, M. R. 1987). More cautious descriptions are required for the implication part of this manuscript unless the authors describe more about the turbulent characteristic at the site.

Minor comments
1. Error or uncertainty analysis on the gradient of HOM would be helpful to convince the reader; more scatter on higher m/z in figure 1 may also derive the large variation in higher m/z in figure 8 and 9. Quantitative description about HOM difference would be plausible to proof the existence of HOM.
2. Address the physical meaning of curve fitting in figure 1.
3. Any temperature, RH, pressure dependence in 1:1 correlation between tower and ground HOM? (I mean figure 3 colored by different variables.)
4. If the authors put the information in Table 1 as box whisker plots, that would be easy to read.
5. Brief mention and more discussion about condensation sink would be helpful to the readers who are not in this field.
6. Difference or ratio plot between tower and ground for figure 7 would be more informative; current plot has many overlaps in points. This part may have a chance to link with figure 8 and 9 for deeper analysis than descriptive results.
7. If possible, I suggest the authors to add figure R1 for all time windows of a day in supplement as a way to prove the gradient in HOM is real.
8. I feel the description about the forest are missed in this manuscript especially for the readers who are not familiar with the site. Description about the canopy structure parameters (i.e. LAI, leaf distribution, tree species etc.) are required not only for the turbulent characteristics but also for the sources and sinks of HOM. I also suggest the authors to add a schematic of the site including the information about all the measurements which took place at the site to ease the reader for that information.
Reference
Raupach, M. R., "A Lagrangian Analysis of Scalar Transfer in Vegetation Canopies." Quarterly Journal of the Royal Meteorological Society 113(475), 107-120, 1987.

Please address the referee #1's concern.