the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 25 Mar 2025
Expanding Observational Capabilities of A Diode-Laser-Based Lidar Through Shot-To-Shot Modification of Laser Pulse Characteristics
Abstract. A method for expanding the observational capabilities of diode-laser-based atmospheric lidar is discussed. A straightforward test, consisting of interleaved "long'' and "short'' laser pulses, was developed to demonstrate how shot-to-shot modification of laser pulse characteristics can enhance the performance of low-power, diode-laser-based lidar and could benefit atmospheric observations. Two examples are given to demonstrate the technique. In the first, water vapor profiling is extended closer to the surface while simultaneously maintaining consistent far-range performance. These results are verified with collocated measurements. In the second example, clouds are resolved at high vertical spatial resolution with high signal-to-noise ratio. Details of the lidar instrument hardware and the method to combine the laser pulses of different durations are given.
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Status: open (until 08 May 2025)
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RC1: 'Comment on egusphere-2025-1288', Julien Totems, 22 Apr 2025
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In this concise article, the NCAR team of Dr. Stillwell improves on the already very successful design of micro-pulse dial proposed in 2021, by adjusting pulse length for two benefits: shortening the minimum range, and obtaining better resolution on fine water vapor, cloud or aerosol structures. This is the first time this has been done to my knowledge as well, because other lidar systems do not have any way to change pulse characteristics during the measurement. The results are promising, if a bit incomplete, and the implications important. The science is sound, and the presentation is good, although some very minor corrections can be made, that I have listed in the attached pdf (comments in the text).
My main concern and proposal for improvement is that, contrary to what is stated, there are indeed techniques to combine low/high resolution (resp) and high/low noise (resp) data, but in the literature of other fields such as imaging or astronomy (please see specific comment in the pdf for more details). As it is now, the paper seems to me a bit light in that specific regard, and it could gain a lot in significance if the authors could add just a trial of one of these techniques at the end of the last section. This remains a personal opinion and more of a wish than a request, but as a lidar scientist I would be extremely interested in seeing them applied to the perfect case study proposed on cloud features in the last section.
This is why I recommend Minor Revisions be made to the article, mostly concerning the last point. I still find the overall paper to be of very good quality.
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RC2: 'Comment on egusphere-2025-1288', Anonymous Referee #2, 25 Apr 2025
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The work by Stillwell et al. presents a method to enhance the observational capabilities of the NCAR water vapor DIAL. By alternating between long and short pulses on a shot-to-shot basis, the technique retrieves water vapor measurements closer to the surface and resolves clouds with high vertical spatial resolution, while maintaining far-range performance.
The manuscript is relevant, well-written, and concise. However, it could benefit from a more quantitative discussion of the magnitude and relative weight of the different uncertainty sources associated with the short-range retrieval (e.g., signal strength changes due to incomplete overlap, background effects). Based on the plots in Figs. 2 and 3, there appears to be a slight low bias below 500 m, which reverses into a high bias between 500 m and 1 km. While the comparison includes only a few radiosondes, a quantitative analysis in the overlapping region between short- and long-pulse retrievals could provide insights into the high bias. Similarly, if available, a comparison with surface humidity measurements and the first ‘valid’ retrieval bin could clarify any potential low bias at the bottom of the short-pulse retrieval.
Lastly, I agree with Julien Totems's comment regarding subsection 1.1; there is no need to separate it from the introduction.
I recommend the manuscript for publication once these minor concerns are addressed.
Citation: https://doi.org/10.5194/egusphere-2025-1288-RC2
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