Standoff Infrared Measurements of Chemical Plume Dynamics in Complex Terrain Using a Combination of Active Swept-ECQCL Laser Spectroscopy with Passive Hyperspectral Imaging
Round 1
Reviewer 1 Report
The manuscript entitled: “Standoff infrared measurements of chemical plume dynamics in complex terrain using a combination of active swept-ECQCL laser spectroscopy with passive hyperspectral imaging” proposed an application of the hyperspectral imaging and active swept-ECQCL technique to detect and classify chemical plume dynamics.
1. Line 279-292: Authors have to revise the whole sentence (or correct citation).
2. Line 310-313: Authors have to revise the whole sentence (or correct citation).
Author Response
Please see our responses to reviewers' comments and the revised manuscript in the attached file.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This paper studies the outdoor plume release measurements in complex terrain through using a passive LWIR-HSI System and an active-mode swept-ECQCL system. The manuscript is well organized. The experiments analyzed different factor effects on chemical plume. Here are some comments.
1. The review wonders how to verify the effectiveness of the proposed method, since there is no other competitor and ground truth for reference.
2. This manuscript is more like an experimental report. The motivation or the contribution is not significant.
3. Some grammar mistakes should be corrected.
Author Response
Please see our responses to the reviewers' comments in the attached document.
Author Response File: Author Response.pdf
Reviewer 3 Report
Review of “Standoff infrared measurements of chemical plume dynamics in complex terrain using a combination of active swept-ECQCL laser spectroscopy with passive hyperspectral imaging”
In this manuscript, the authors present results from outdoor plume measurements of SF6 and F152a in a complex terrain, with plume detection using two complementary remote (1.5 km distance) measurement techniques—the first based on passive long-wave infrared high speed imaging, and the other based on wavelength-scanned laser absorption spectroscopy. The authors studied two different plume propagation configurations with gas releases at two locations. For both measurement systems, spectral and temporal resolution was high enough to provide for sensitive measurements of SF6 over a period of time corresponding to the gas release, while only the absorption spectroscopy-based method was sensitive enough to assess time-evolution of F152a. The authors found that traditional Gaussian plume models are lacking in their predictions when local topography and wind variations are involved in such a measurement. The measurement techniques are high quality and demonstrate high potential for application in remote sensing environments, and the challenges associated with the experimental setup overcome by the others to produce the data are commendable. The authors provide a nice appendix as well to describe the signal processing methods as well as provide insights into the uncertainties and sensitivities of their measurements.
As a demonstration of a sensing method (a detailed analysis of plume dispersion patterns would be outside the scope of this paper), the paper is acceptable for publication pending minor revisions to the manuscript.
- The spectra of SF6 and F152a, the cross-sections of which are available in the PNNL database at multiple temperatures, are shown for specific temperatures only. It is conceivable that the temperature across the line-of-sight measurement here (2 x 1.5 km) is not uniform, and thus the measured spectra are subject to some interpretative error. The authors should provide some comments on estimating measurement uncertainty (perhaps relative %) owing to expected temperature variation across the line of sight.
Author Response
Please see attached responses to the reviewers' comments.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Thanks for authors' careful response. The questions have been answered well. The reviewer has no more questions.
