the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 11 Apr 2024
An Economical Tunable-Diode Laser Spectrometer for Fast-Response Measurements of Water Vapor in the Atmospheric Boundary Layer
Abstract. The high spatiotemporal variability of water vapor in the atmospheric boundary layer possesses a significant measurement challenge with abundances varying by an order of magnitude over short spatial and temporal scales. Herein, we describe the design and characterization of an economical and flexible fast-response instrument for measurements of water vapor the atmospheric boundary layer (ABL). The in-situ method of tunable-diode laser spectroscopy (TDLS) in the mid-infrared was chosen based on a heritage with previous instruments developed in our laboratory and flown on research aircraft. The instrument is constructed from readily available components and based on low-cost distributed feedback laser diodes (DFB) that enjoy widespread use for high-speed fiber-optic telecommunications. A pair of versatile, high-speed ARM-based microcontrollers drive the laser and acquire and store data. High precision and reproducibility are obtained by tight temperature regulation of the laser via a miniature commercial proportional integrating (PI) controller. The instrument can be powered by two rechargeable 3.5 V lithium-ion batteries, consumes less than 5 W, weighs under 1 kg, and is comprised of hardware costing less than $3,000. The new TDLS agrees within 2 % compared to a laboratory standard and displays a precision of 10 ppm at a sample rate of 10 Hz. The new instrument allows users with little previous experience in instrumentation to acquire high quality, fast-response observations of water vapor for a variety of applications. These include frequent horizontal and vertical profiling by uncrewed aerial vehicles (UAVs), long-term eddy covariance measurements from fixed and portable flux towers, and routine measurements of humidity from weather stations in remote locations such as the polar ice caps, mountains, and glaciers.
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Status: closed
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RC1: 'Comment on amt-2024-34', Anonymous Referee #1, 05 Jun 2024
The manuscript describes the promising development of a low-cost, fast-response tunable-diode laser spectrometer for measuring water vapor in the atmospheric boundary layer. As the instruments hard and the software design is based on readily available components, lightweight, and energy-efficient it can be easily reproduced and exhibits a broad spectrum of potential atmospheric measurement applications. The laboratory calibration and first atmospheric measurements show a high accuracy and precision of 10 ppm at 10Hz allowing for sampling with high spatial and temporal resolution.
General:
- The consistency of naming should be improved throughout the manuscript. Some names are changed multiple times as an example: Teensy = Teensy 4.1 = data collection microcontroller = receiver. Also introduced acronyms should be used or left out. More consistency here would be very helpful.
- The quality of language/sentence syntax should be improved. Many typos, slips of the pen, and complicated/convoluted sentences.
- The plotting ticks should be changed using to a more standard style as they are confusing that way. E.g.: Fig 5, yaxis highest tick should be 30, above the axis a common coefficient with 1x10-3
- Also cross check references if missing and use correct citation style: Textual citation XXX et al. (YYYY) vs. parenthetical citations (XXX etl al. YYYY)
2.1 Hardware Description
- The captions of Fig.1 to Fig. 3 should be extended to be self-explanatory and not reference to the text.
For example: Fig 1, please explain the different components shown: are drive input and TEC input circuits by themselves, how does the TIA look, are the laser driver and data collection unit the two Teensy microcontrollers…
- L 103: The laser wavelength is tuned via temperature?
- L 105: add ± before 0.002 K
- L 127: adapt trigger pulse direction in Fig 1. From driver to data collection if the text is correct
- L129: After 5V reference to figure
- L 141 – 146: Please clarify: Was the laser collimated or divergent? How much bigger is the laser beamwidth compared to the InGaAs sensor active area? Have there been any tests regarding vibrations? (Even collimated laser beams show a distinct Gaussian profile which could induce signal variations upon vibration)
- L 149: Syntax wrong or double sentence
2.2 Spectral Processing
- L 163: please cross check values on where the offset/drift is determined 30 & 20 points vs. 10 point in fig 4 caption.
- L 165 – 169: This part requires more clarification on how to convert scan steps into wavelength.
- L 170: What do you want to say with the “[..] are then placed in an array?
- Fig4 (b) Unit should be wavenumber
3. Results:
- Fig 5: Does the x-axis represent values measured by the Picarro or converted values from the TDLS?
Please also state the lin-regress function parameters (slope, intercept, r2) or a plot of the converted H2O-ppm from TDLS over H2O-ppm measured by the Picarro together with a 1:1 line and respective regression slope. Similar as for Figure 8 (b)
- L 216 – 220: This part needs more clarification. Was a different InGaAs sensor used for the calibration of the instrument than the actual measurement? That could yield a different conversion coefficient.
- L 239: Wu et al 2015 citation not present in references
- Fig8 (a). Please convert the x-axis to actual time in UTC
- L 278: Doesn't the averaging over 30s smooth all variation on a spatial scale of 1.5m? Hence I am not surprised that that values align even the locations had a 1.5m separation.
Some Typos:
- L 104: remove dot after “([…], MT)”
- L 111: add quotes “ after receiver
- L 122: resister -> resistor
- L 209: remove dot after “(black points)”
- L 256: lowercase a before 25-m long
- L 298: Remove dot after power
- L 320: mission word(s) after water
- L 325: Either tested or powered
- L 333: remove with before TEC
- L 337 delete “configuring for use”
- L 342: ABL was already introduced in the introduction
Citation: https://doi.org/10.5194/amt-2024-34-RC1 - AC1: 'Reply on RC1', Emily Wein, 07 Jun 2024
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RC2: 'Comment on amt-2024-34', Anonymous Referee #2, 20 Jun 2024
The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2024-34/amt-2024-34-RC2-supplement.pdf
- AC2: 'Reply on RC2', Emily Wein, 09 Jul 2024
-
EC1: 'Editor Comment on amt-2024-34', Ulrich Platt, 10 Jul 2024
Dear Authors,
As you certainly noticed, both reviewers provided positive judgements of your manuscript although noting many minor points that should be corrected.
From your responses to the reviewers’ comments it is clear that you will attempt to make all requested changes to the manuscript.
Therefore and in view of the positive reviews I like to encourage you to provide a revised version of the manuscript for the final decision on acceptance.
At this point I should like to encourage you to actually include all relevant circuit diagrams (as suggested by referee #2) and to perhaps expand the discussion of the role of new applications that have been limited in the past by high cost of instrumentation. Final comment: You may want to check again whether in Fig. 2 the labeling of the two inputs (+ and -) of the operational amplifier is correct.
With very best regards
Ulrich Platt
Citation: https://doi.org/10.5194/amt-2024-34-EC1 -
AC3: 'Reply on EC1', Emily Wein, 11 Jul 2024
We thank the Editor for additional comments.
We will incorporate the suggestions in the revised manuscript, including additional circuit details as suggested by one of the reviewers.
Citation: https://doi.org/10.5194/amt-2024-34-AC3
-
AC3: 'Reply on EC1', Emily Wein, 11 Jul 2024
-
EC2: 'Comment on amt-2024-34', Ulrich Platt, 23 Sep 2024
The authors submitted a substantially revised version on the basis of the reviewers’ comments.
However, after reading the revised version, I find that quite a number of points still do need improvement, for instance:
The sentence in lines 58-61 introducing the new instrument is very hard to read (in fact the sentences in the original version of the manuscript were better in that respect):
“As fast in situ observations of H2O are essential for numerical weather prediction and for investigations of the evolution of the ABL and its turbulence characteristics (e.g. large eddy simulations), and there is a need for more frequent measurements from remote locations, we have developed an economical new fast-response laser spectrometer (Helbig et al., 2021; Petersen, 2016).”
Line 65: The term „capacitive sensors” appears to correspond to “thin-film water-sensitive polymers sandwiched between two electrodes” in lines 53-54. This should be made clear.
Lines 83-84: The meaning of „heterogeneous scalar and vector fields resulting from complex terrain“ remains cryptic. If H2O mixing ratio (scalar) fields and H2O flux (vector) fields are meant this should be spelled out clearly.
Line 105 (Caption of Fig. 1): What does the dashed line (there appears to be no dotted line) actually indicate ?
Line 125: Explain “a Teensy 3.6“. Is this one of the Arduino micocontrollers mentioned above?
Line 141: What does the term „Teensy 4.1“ refer to?
Line 179: Give figures also in nm.
Figure 3 (new): Lower right corner: TIP32AG is designated PNP transistor, but the symbol indicates an NPN transistor (which is probably correct from the schematics, so transistor type designation is probably wrong), perhaps TIP31AG.
Unfortunately this list can be extended.
Furthermore the „track changes“ document is not very helpful in that several sections of the text are marked as changed while they are actually unchanged (e.g. most of lines 58 and 59). At the same time several changes (e.g. the caption of the new Fig. 3) are not marked as changed although they are clearly new text.
Also the line numbers given in the answer to the reviewers do not appear to match the text.
Overall, I am sorry to have to conclude that the revised manuscript is still not ready for acceptance for final publication in AMT.
I therefore suggest:
1) That the authors provide a further revise version after thoroughly going through the text and taking care of the unclear statements and errors. In this context it might be helpful if a more senior scientist (co-author) could help.
2) That the authors provide a „track changes“ version that shows all changes (and only the changes) with correct line numbers.
Alternatively, the authors may re-submit a revised version of the manuscript to AMT.
Citation: https://doi.org/10.5194/amt-2024-34-EC2 -
AC4: 'Reply on EC2', Emily Wein, 04 Oct 2024
The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2024-34/amt-2024-34-AC4-supplement.pdf
-
AC4: 'Reply on EC2', Emily Wein, 04 Oct 2024
Status: closed
-
RC1: 'Comment on amt-2024-34', Anonymous Referee #1, 05 Jun 2024
The manuscript describes the promising development of a low-cost, fast-response tunable-diode laser spectrometer for measuring water vapor in the atmospheric boundary layer. As the instruments hard and the software design is based on readily available components, lightweight, and energy-efficient it can be easily reproduced and exhibits a broad spectrum of potential atmospheric measurement applications. The laboratory calibration and first atmospheric measurements show a high accuracy and precision of 10 ppm at 10Hz allowing for sampling with high spatial and temporal resolution.
General:
- The consistency of naming should be improved throughout the manuscript. Some names are changed multiple times as an example: Teensy = Teensy 4.1 = data collection microcontroller = receiver. Also introduced acronyms should be used or left out. More consistency here would be very helpful.
- The quality of language/sentence syntax should be improved. Many typos, slips of the pen, and complicated/convoluted sentences.
- The plotting ticks should be changed using to a more standard style as they are confusing that way. E.g.: Fig 5, yaxis highest tick should be 30, above the axis a common coefficient with 1x10-3
- Also cross check references if missing and use correct citation style: Textual citation XXX et al. (YYYY) vs. parenthetical citations (XXX etl al. YYYY)
2.1 Hardware Description
- The captions of Fig.1 to Fig. 3 should be extended to be self-explanatory and not reference to the text.
For example: Fig 1, please explain the different components shown: are drive input and TEC input circuits by themselves, how does the TIA look, are the laser driver and data collection unit the two Teensy microcontrollers…
- L 103: The laser wavelength is tuned via temperature?
- L 105: add ± before 0.002 K
- L 127: adapt trigger pulse direction in Fig 1. From driver to data collection if the text is correct
- L129: After 5V reference to figure
- L 141 – 146: Please clarify: Was the laser collimated or divergent? How much bigger is the laser beamwidth compared to the InGaAs sensor active area? Have there been any tests regarding vibrations? (Even collimated laser beams show a distinct Gaussian profile which could induce signal variations upon vibration)
- L 149: Syntax wrong or double sentence
2.2 Spectral Processing
- L 163: please cross check values on where the offset/drift is determined 30 & 20 points vs. 10 point in fig 4 caption.
- L 165 – 169: This part requires more clarification on how to convert scan steps into wavelength.
- L 170: What do you want to say with the “[..] are then placed in an array?
- Fig4 (b) Unit should be wavenumber
3. Results:
- Fig 5: Does the x-axis represent values measured by the Picarro or converted values from the TDLS?
Please also state the lin-regress function parameters (slope, intercept, r2) or a plot of the converted H2O-ppm from TDLS over H2O-ppm measured by the Picarro together with a 1:1 line and respective regression slope. Similar as for Figure 8 (b)
- L 216 – 220: This part needs more clarification. Was a different InGaAs sensor used for the calibration of the instrument than the actual measurement? That could yield a different conversion coefficient.
- L 239: Wu et al 2015 citation not present in references
- Fig8 (a). Please convert the x-axis to actual time in UTC
- L 278: Doesn't the averaging over 30s smooth all variation on a spatial scale of 1.5m? Hence I am not surprised that that values align even the locations had a 1.5m separation.
Some Typos:
- L 104: remove dot after “([…], MT)”
- L 111: add quotes “ after receiver
- L 122: resister -> resistor
- L 209: remove dot after “(black points)”
- L 256: lowercase a before 25-m long
- L 298: Remove dot after power
- L 320: mission word(s) after water
- L 325: Either tested or powered
- L 333: remove with before TEC
- L 337 delete “configuring for use”
- L 342: ABL was already introduced in the introduction
Citation: https://doi.org/10.5194/amt-2024-34-RC1 - AC1: 'Reply on RC1', Emily Wein, 07 Jun 2024
-
RC2: 'Comment on amt-2024-34', Anonymous Referee #2, 20 Jun 2024
The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2024-34/amt-2024-34-RC2-supplement.pdf
- AC2: 'Reply on RC2', Emily Wein, 09 Jul 2024
-
EC1: 'Editor Comment on amt-2024-34', Ulrich Platt, 10 Jul 2024
Dear Authors,
As you certainly noticed, both reviewers provided positive judgements of your manuscript although noting many minor points that should be corrected.
From your responses to the reviewers’ comments it is clear that you will attempt to make all requested changes to the manuscript.
Therefore and in view of the positive reviews I like to encourage you to provide a revised version of the manuscript for the final decision on acceptance.
At this point I should like to encourage you to actually include all relevant circuit diagrams (as suggested by referee #2) and to perhaps expand the discussion of the role of new applications that have been limited in the past by high cost of instrumentation. Final comment: You may want to check again whether in Fig. 2 the labeling of the two inputs (+ and -) of the operational amplifier is correct.
With very best regards
Ulrich Platt
Citation: https://doi.org/10.5194/amt-2024-34-EC1 -
AC3: 'Reply on EC1', Emily Wein, 11 Jul 2024
We thank the Editor for additional comments.
We will incorporate the suggestions in the revised manuscript, including additional circuit details as suggested by one of the reviewers.
Citation: https://doi.org/10.5194/amt-2024-34-AC3
-
AC3: 'Reply on EC1', Emily Wein, 11 Jul 2024
-
EC2: 'Comment on amt-2024-34', Ulrich Platt, 23 Sep 2024
The authors submitted a substantially revised version on the basis of the reviewers’ comments.
However, after reading the revised version, I find that quite a number of points still do need improvement, for instance:
The sentence in lines 58-61 introducing the new instrument is very hard to read (in fact the sentences in the original version of the manuscript were better in that respect):
“As fast in situ observations of H2O are essential for numerical weather prediction and for investigations of the evolution of the ABL and its turbulence characteristics (e.g. large eddy simulations), and there is a need for more frequent measurements from remote locations, we have developed an economical new fast-response laser spectrometer (Helbig et al., 2021; Petersen, 2016).”
Line 65: The term „capacitive sensors” appears to correspond to “thin-film water-sensitive polymers sandwiched between two electrodes” in lines 53-54. This should be made clear.
Lines 83-84: The meaning of „heterogeneous scalar and vector fields resulting from complex terrain“ remains cryptic. If H2O mixing ratio (scalar) fields and H2O flux (vector) fields are meant this should be spelled out clearly.
Line 105 (Caption of Fig. 1): What does the dashed line (there appears to be no dotted line) actually indicate ?
Line 125: Explain “a Teensy 3.6“. Is this one of the Arduino micocontrollers mentioned above?
Line 141: What does the term „Teensy 4.1“ refer to?
Line 179: Give figures also in nm.
Figure 3 (new): Lower right corner: TIP32AG is designated PNP transistor, but the symbol indicates an NPN transistor (which is probably correct from the schematics, so transistor type designation is probably wrong), perhaps TIP31AG.
Unfortunately this list can be extended.
Furthermore the „track changes“ document is not very helpful in that several sections of the text are marked as changed while they are actually unchanged (e.g. most of lines 58 and 59). At the same time several changes (e.g. the caption of the new Fig. 3) are not marked as changed although they are clearly new text.
Also the line numbers given in the answer to the reviewers do not appear to match the text.
Overall, I am sorry to have to conclude that the revised manuscript is still not ready for acceptance for final publication in AMT.
I therefore suggest:
1) That the authors provide a further revise version after thoroughly going through the text and taking care of the unclear statements and errors. In this context it might be helpful if a more senior scientist (co-author) could help.
2) That the authors provide a „track changes“ version that shows all changes (and only the changes) with correct line numbers.
Alternatively, the authors may re-submit a revised version of the manuscript to AMT.
Citation: https://doi.org/10.5194/amt-2024-34-EC2 -
AC4: 'Reply on EC2', Emily Wein, 04 Oct 2024
The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2024-34/amt-2024-34-AC4-supplement.pdf
-
AC4: 'Reply on EC2', Emily Wein, 04 Oct 2024
Model code and software
TDLS Arduino Sketches and Extraction codes Emily Wein https://github.com/emiwein/TDLS_code
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