the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 01 Oct 2024
The SAIL dataset of marine atmospheric electric field observations over the Atlantic Ocean
Abstract. A unique dataset of marine atmospheric electric field observations over the Atlantic Ocean is described. The data are relevant not only for atmospheric electricity studies, but more generally for studies of the Earth's atmosphere and climate variability, as well as space-earth interactions studies. In addition to the atmospheric electric field data, the dataset includes simultaneous measurements of other atmospheric variables, including gamma radiation, visibility, and solar radiation. These ancillary observations not only support interpretation and understanding of the atmospheric electric field data, but are also of interest in themselves. The entire framework from data collection to final derived datasets has been duly documented to ensure traceability and reproducibility of the whole data curation chain. All the data, from raw measurements to final datasets, are preserved in data repositories with a corresponding assigned DOI. Final datasets are available from the Figshare repository (https://figshare.com/projects/SAIL_Data/178500) and computational notebooks containing the code used at every step of the data curation chain are available from the Zenodo repository (https://zenodo.org/communities/sail).
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RC1: 'Comment on essd-2024-245', Anonymous Referee #1, 24 Oct 2024
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This document is very clear in its description of valuable measurements made from a Portuguese ship in the Atlanic Ocean. Important "clean" data sets are provided. I congratulate the authors, and I hope that their observations will be further used for research purposes.
I only found one error; on line 222, "dully "should be replaced by "duly".
Citation: https://doi.org/10.5194/essd-2024-245-RC1 -
RC2: 'Comment on essd-2024-245', Earle Williams, 14 Nov 2024
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Review of “The SAIL dataset of marine atmospheric electric field observations over the Atlantic Ocean” by Susana Barbosa et al.
Susana Barbosa has devoted valuable attention to making scientific observations from a Portuguese Navy ship. I this work the emphasis lies with the measurement of the fair-weather electric field. At a time of resurging interest in the monitoring of the global electric circuits, these efforts are most welcome. The work definitely deserves to be published, but some suggestions come to mind for improving the final submission. These substantive issues are followed by detailed comments/edits on the text.
Summary: Publish after major revision
Substantive Issues:
- Sources for the DC global circuit
Thunderstorms are given emphasis (page 1, line 14) as the source for the global circuit, but recent work by Mach et al. (2009, 2010) have substantiated the prescient suggestions of CTR Wilson (1921), a paper cited by the authors, that electrified shower clouds may play an equally important role. It is recommended that the authors study the relevant sections of Wilson (1921) and then modify their Introduction slightly.
- Absolute calibration of electric field
The one aspect of this work in most need of additional attention is the absolute calibration. And this is never a trivial task. The E field magnitudes in Figures 5, 6, 8 and 9 are low. The Carnegie Curve” field is low by roughly a factor of two. This reviewer needs clarification of procedure. The very best thing to have done is to place the second sensor “on shore” but perhaps more rigorously than what is reported in line 136 on page 6, to mount the CS-110 flush-mounted on a large planar surface on the dock and well out of influence of the mast and rigging of the ship. (If flush-mounted the makers of the CS-110 have a sound procedure for absolute calibration.) Then one makes simultaneous recordings on shore (i.e., the flat dock) and on the ship mast in fair weather conditions to get the best form-factor for the ship’s installation. The shore measurement is the absolute reference.
The procedure described above is exactly what members of the Carnegie Institution did with the calibration of the E field on the Maude, though instead of using a flat dock, they used the flat Arctic ice sheet in the vicinity of the ship, when it was locked in the ice.
Now if this rigorous procedure has not been undertaken, I am not quite sure what to suggest. One could adjust the mean value in Figure 6 to match the Carnegie ship measurements, or more recent ones undertaken by Wilson and Cummins (2021) on measurements made (also with CS-110 instruments) on buoys at sea off the coast of Florida.
Wilson, J. G., & Cummins, K. L. (2021). Thunderstorm and fair-weather quasi-static electric fields over land and ocean. Atmospheric Research, 257, 105618. https://doi.org/10.1016/j.atmosres.2021.105618
Neither adjustment may be appealing to the authors, so I am hoping the more rigorous treatment has been pursued, or could still be pursued. The mean values of 119 V/m reported in line 140 (page 7) is close to the Carnegie mean value of 130 V/m and in Figure 7 I see an eyeball mean near 120 V/m. So now I wonder if this normalization was applied to the analysis in Figure 9, why isn’t the mean value roughly twice what is shown here?
I do think something can be done to improve the situation overall.
- Spikes in Figure 6
Isn’t it likely that the spikes in Figure 6 in the purple record for the pier are due to cultural activity on the pier near the CS-110 that could not be completely suppressed?
- Selection of common time series for two scenarios
I think data plots of the kind shown in Figure 6 transformed to a scatterplot in Figure 7 is a a good way to calibrate one field recording against another. I would suggest however the calculation of a formal correlation coefficient between the two records as further quantitative evidence that you are measuring (mostly) a common E field imposed on both instruments.
- Confusion about data “while navigating” and “in port”
Here I cited line 70 on page 3 and line 86 on page 4. In Figure 2, does the “land” flag mean being in port and not under sail (“navigating”. Please clarify all in the text.
- Energy bandwidth of gamma ray source
The information provided in line 63 on page 3 is relevant to an earlier interest on the reviewer’s part in seeing whether electron runaway may have been occurring during precipitation events at sea. However, the rather low min value for gamma ray energy (475 keV) will allow for radon daughter products and that could dominate any event. To be more certain about real electron runaway, this lower threshold would be need to be substantially higher. See also Chilingarian (2018).
Chilingarian, A. (2018). Long lasting low energy thunderstorm ground enhancements and possible Rn-222 daughter isotopes contamination. Physics Review D, 98, 022007. https://doi.org/10.1103/physrevd.98.022007
Detailed comments/edits on the text:
Page 1
Line 14 Add “and electrified shower clouds”
Line 22 “variation of global thunderstorm activity”
Page 23 delete “throughout the Earth”
Page 2
Line 24 change “at the end of the day” to “late in the day”
Line 27 “came to be known”
Line 28 Can also cite Markson (BAMS, 2007)
Line 31 “The need for such observations…”
Line 34 Interesting. I had forgotten about this. That should be checked again sometime, maybe by this group.
Line 41 The inclusion of a photo of the ship with mast and rigging would be helpful here.
Line 44 “arrived in Lisbon”
Line 48 Why is the microsecond precision so important for your endeavors here?
Line 53 Suggest change from “rotating” to “oscillating”
Line 53 “at a height”; No problem of E field shielded by conductive rigging?
Line 56 I think you need more details about “radon gas progeny” (the same suggestion I made for your other recent manuscript).
Page 3
Lines 59-61 Think you need to tie together better the visibility variable and the conductivity variable, with aerosol being the key physical linkage.
Line 65 Clarify why “pointing upwards”?
Line 68 Is the outgoing also shortwave, or rather longwave radiation?
Page 4
line 74 change “voids” to “missing segments”
line 78 “to foster their reuse”
line 86 This seems contradictory with line 70 on the previous page.
Figure 2 caption should tell what total time was involved.
Line 94 2 meter height over flat terrain? (Your procedure is not entirely clear to me.)
Page 5
Lines 102-103 Your procedure is not completely clear to me
Line 106 4 V/m is a small fraction of typical fair weather fields
Figure 3: minor DC offsets
Figure 4: only Campbell (CS-110) people will know how to interpret these results (and me!)
Page 6
Line 112 Suggest adding: “The electric field is downward-directed in fair weather conditions”
Line 118 “applying these procedures to the raw data”
Line 133 This suggests that only height is included but it is more complicated than that I think.
Lines 135-136 Use of photos here would be helpful.
Line 138 Calculation of correlation coefficient would be helpful here.
Page 7
Line 141 Quantify the correlation.
Figure 6 caption: Add a statement about the weather condition for this short period of data.
Page 8
Figure 7 What is the origin of the points beneath the main linear scatter? It would be useful to give the overall correlation coefficient.
Line 150 What are the details of the height-corrected data?
Line 156 “as a fully-ocean day”
Page 9
Line 162 Are “marine observations” all ocean days?
Line 166 Add a sentence about the quantitative comparison: the Carnegie curve amplitude variation is +/- 15% as I recall.
Figure 9 is a very valuable result, but it would be nice if the absolute field were more accurate (see earlier remarks in item (2) above.
Line 172 This reminds me of the spike in Figure 6 (top record). What do you attribute that to?
Line 174 What is the “jupyter notebook”?
Page 10
Line 175 “what is “Zenodo”?
Figure 10 What do you think causes the spikes? Could they be chunks of radioactivity coming over? The first author is well-suited to answering this question.
Line 184 “are consistently high” They are constant. Discuss that limit (40 km) (see line 67 on page 3)
Page 11
Figures 11 and 12 Why not show solar radiation for the same two days shown for visibility? This would help point up the internal consistency of the overall data archive.
Line 204 “jupyter notebook”???
Page 12
Line 213 “include”
Line 222 “duly” ???
Section 5 Should this follow the Conclusions, or rather appear in an Appendix?
Page 14
What did the Portuguese Navy get out of the useful project?
End review
Earle Williams
Citation: https://doi.org/10.5194/essd-2024-245-RC2
Data sets
SAIL - Fair weather atmospheric electric field data Susana Barbosa et al. https://figshare.com/articles/dataset/SAIL_-_Fair_weather_atmospheric_electric_field_data/26022001
SAIL - Atmospheric electric field data Susana Barbosa et al. https://figshare.com/articles/dataset/SAIL_-_Atmospheric_electric_field_data/19692391
Pre-processed atmospheric data from the SAIL campaign onboard the Sagres ship Susana Barbosa et al. https://rdm.inesctec.pt/es/dataset/nis-2023-007
SAIL - Solar radiation data Susana Barbosa et al. https://figshare.com/articles/dataset/SAIL_-_Solar_radiation_data/24614754
SAIL - Visibility data Susana Barbosa et al. https://figshare.com/articles/dataset/SAIL_-_Visibility_data/19692394
SAIL - gamma radiation data Susana Barbosa et al. https://figshare.com/articles/dataset/SAIL_-_gamma_radiation_data/20393931
Interactive computing environment
SAIL Jupyter Notebooks - Pre-processing and quality-control of gamma radiation data from the SAIL project Susana Barbosa https://doi.org/10.5281/zenodo.11620014
SAIL Jupyter Notebooks - Pre-processing of visibility data from the SAIL project Susana Barbosa https://doi.org/10.5281/zenodo.11621789
SAIL Jupyter Notebooks - Pre-processing of meteorological data from the SAIL project Susana Barbosa https://doi.org/10.5281/zenodo.10150266
SAIL Jupyter Notebooks - Pre-processing and quality-control of solar radiation data from the SAIL project Susana Barbosa https://doi.org/10.5281/zenodo.10161091
SAIL Jupyter Notebooks - Pre-processing and quality-control of electric field data from the SAIL project Susana Barbosa https://doi.org/10.5281/zenodo.10276613
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