Effect of UV Scattering on Detection Limit of SO2 Cameras
Round 1
Reviewer 1 Report
The manuscript “Effect of UV Scattering on Detection Limit of SO2 Cameras” analyzes the relevant factors which affect the detection accuracy of SO2 cameras. According to the authors, atmospheric visibility and detection distance are the main factors that cause measurement errors, but these errors can be effectively improved by some correction methods.
The paper is globally well written, presents in a concrete way the contributions of the manuscript to the referred state of the art. The theoretical background is almost clear and the experimental setup is well described. However, the principal problem that I encountered when I read the manuscript was that it was not clear for me to understand some procedures to perform the simulations and the calibrations itself.
For example,
1. Is the uncorrected filter transmittance curve in Figure 2 from the experimental one? Why the transmissivity of the curve without correction is higher than that of the curve after correction?
2. Line 241: The authors say that “The central wavelength varies between 300 and 310 nm”, however, the X-axis range shown in Figure 3 is significantly larger?
3. What is the definition of Limitation that is present on Y-axis of Figs. 5, 6 and 7? Are the authors referring to Detection Limit?
4. In Line 426, the sensitivity of the UV camera to detect SO2 concentration is dependent heavily on the optical depth of the carbon black particles. But authors concluded in line 420 that the effect of aerosol extinction on the SO2 concentration detection limit can often be ignored in actual measurement experiments. Therefore, it seems to be contradictory. Does the following correction of ship exhaust images consider the influence of aerosols?
5. Where the filters are placed into the system? Is in between the lens and the sensor?
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript “Effect of UV Scattering on Detection Limit of SO2 Cameras” proposes a correction model for light dilution effect to effectively improve the detection limit of the camera system. Also, authors discussed an image processing method that can liberate the camera's performance. Some detailed comments are given as follows.
1. The manuscript may need to unified explanation of terms. For example, in line 73, “which can further reduce the effect of optical dilution on the calibration accuracy of UV cameras”. The “optical dilution” should be changed to “light dilution”.
2. Change the filter transmittance symbol “ ” on line 184 to reflect the transmittance as a function of wavelength.
3. In Lines 267 and 396, there are some blank areas in the figures. Could the authors explain why there is no data?
4. The authors say that “To obtain a calibration curve that fully considers the actual radiative transfer process, this SO2 UV camera system is equipped with a DOAS and placed between the two cameras.” The spectra acquired by the spectrometer were also corrected for light dilution problem? If not, what is the function of the spectrometer here?
5. Figure 12, 13,14 and 15. The Y-axis should have the same ranges, i.e., have one fixed scale. This would make it easier to distinguish the detection limits under different environmental conditions.
6. I think that this could be applied not only for ship-plumes, but also in situations in which the FOV of the system is not completely covered by the SO2 plume (like industrial emissions). Perhaps this can be mentioned in the abstract.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
