the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 07 May 2024
Historical evolution of the geomagnetic declination at the Royal Observatory of Madrid
Abstract. The agonic line, representing geomagnetic declinations of 0°, recently crossed the Royal Observatory of Madrid (ROM) in December 2021, causing a shift in declination values from west to east. This event constitutes a notable milestone for this significant place, where the first geomagnetic observation series in Spain commenced around 1855. Consequently, a thorough investigation into the historical evolution of the declination has been undertaken to decipher prior occurrences of the agonic line crossing at the ROM. Despite the ROM hosted the first series of geomagnetic measurements in Spain, the present lack of geomagnetic measurements in this observatory makes necessary to extend the declination measurements to other observatories distributed throughout the Iberian Peninsula to better define the passage of the agonic line since 1855 up to the present. For periods prior to 1855, a bibliographic search for declination measurements conducted in the Iberian Peninsula has been carried out, complemented by historical data from the HISTMAG database. As a result, a time-continuous curve of geomagnetic declination is generated from 1590 to 2021 at the ROM coordinates. The declination curve reveals that the agonic line also crossed the ROM 400 years ago (around 1600) passing from west to east declination values.
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RC1: 'Comment on hgss-2024-6', Mioara Mandea, 23 May 2024
This manuscript presents a tour of measurements realised over Iberian Peninsula, with a focus on Royal Observatory of Madrid. The information are interesting and somehow unique. Nevertheless, I am in the inevitability to recommend a major revision of this manuscript. It has to be re-worked to attain an acceptable level for publication in HGSS.
Specific comments
- The paper structure needs to be revisited, with a clear introduction, a section dedicated to ROB where all information about it are gathered, a section on other Spanish observatories, a result session to show different comparisons between observatories and with models, before concluding.
- This manuscript invokes to provide an historical evolution of the geomagnetic declination at the Royal Observatory of Madrid. In describing the history it is needed to tell more about the first instruments (e.g. lines 74-77 – which kind of magnetometers of inclinometers, etc). Figure 5 shows an inclinometer, maybe some others photos can be provided?
- Many information are difficult to read. For example, in the section “Observatory data selection” I suggest the authors to draw a map with the used observatories. It would be nice to provide a table gathering the main information (observatory name, iaga code, coordinates, starting time - closing time, instruments, data availability - minutes, hourly, monthly, annual, etc).
- Some figures need to be revisited. E.g.
- In Figure 4 the comparison with the gufm1 model is presented, but this model is not built to describe variations on daily basis. Moreover, the difference is not du only to crustal field, but maybe to other factors, as unmodelled contributions or errors in measurements. To compute the crustal field (which can be considered constant in time) I suggest you to adapt methods proposed in the literature.
- Figures indicating series and comporting many plots may be view over the same time-span (min _ max of the series). This refers mainly to figures 7, 11.
- Coimbra observatory has a long series of observation. A comparison with the series published in 2021 (and not cited), can bring interesting information and discussions.
- The IGRF model is invoked (line 369), without citations. This choice is not very clear, and I wonder why not to use the gufm1 and COV-OBS models, only.
- The last session needs to be revisited, to get into some real discussions/ conclusions. The section on ROM observatories has to include the Table 1 and the Figure 16. At the end of the paper we would expected some interpretation of the observed secular variation curves.
Finally, efforts are needed to improve the English. Some parts are difficult to read: e.g. abbreviation used and not defined or defined after some pages, as IGN; “Declination data is translated from SPT to ROM » - data are not translated, they are adjusted; some expressions are not clear (“Note that the solar activity is not recorded before 1700 due to the scarce number of declination data”). I encourage the authors to work on the manuscript to provide a more fluid reading.
Some references:
Mandea, M. and Langlais, B. (2002) Observatory Crustal Magnetic Biases during MAGSAT and Oersted Satellite Missions. Geophysical Research Letters, 29.
Morozova, A. L., Ribeiro, P., and Pais, M. A.: Homogenization of the historical series from the Coimbra Magnetic Observatory, Portugal, Earth Syst. Sci. Data, 13, 809–825, https://doi.org/10.5194/essd-13-809-2021, 2021
Citation: https://doi.org/10.5194/hgss-2024-6-RC1 -
AC1: 'Reply on RC1', Jose Manuel Tordesillas, 29 May 2024
Many thanks to Dr. Mioara Mandea for the modifications suggested to improve the quality of our work.
We will review and revise the manuscript taking into account your suggestions.
In the coming days, we will upload a new version of the manuscript and a response letter answering to your comments.
Citation: https://doi.org/10.5194/hgss-2024-6-AC1 - AC4: 'Reply on RC1', Jose Manuel Tordesillas, 19 Jun 2024
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RC2: 'Comment on hgss-2024-6', Tohru Araki, 31 May 2024
The contour line of zero geomagnetic declination always exists somewhere on the Earth's surface. The fact that it passes through a certain point at a certain time has no special physical meaning. On the other hand, it is meaningful to know when the geomagnetic declination becomes zero at a specific observation point that has played a historical role in measuring the geomagnetic field, because it adds new data to the geomagnetic record accumulated at that observation point.
The main objective of this paper is to determine the date and time of occurrence of zero declination at the Royal Madrid Observatory（RMO）, the first observatory in Spain to begin routine geomagnetic observations, and in relation to this, to summarize the distribution and temporal changes of declination in the Iberian Peninsula and its surrounding areas, as well as the history of the scattered observatories.
The structure of the paper is reasonable but there is room for improvement to make it easier for the casual reader to understand.
- The font on the diagrams is too small.
- The full names should be included in parentheses when their abbreviations appear at first.
- Locations of the observatories referred should be shown on the map. This could be included in Figure 8.
- Figure 4: The time variation is unclear. The vertical scale should be changed so that the variation is clearer.
- lines 24 and 31：What "Supplementary Material" do refer to?
- Lines 25-26: "that this observatory does not have a great tradition on geomagnetism"): What does this mean? Is RMO not important?
- Figure 2 : Zero declination horizontal line should be indicated.
- A brief explanation of the geomagnetic database (HISTMAG, gufmq1model), is necessary
- Is it possible to know the date and location of the first self-recording magnetometer observations?
Citation: https://doi.org/10.5194/hgss-2024-6-RC2 - AC3: 'Reply on RC2', Jose Manuel Tordesillas, 19 Jun 2024
-
EC1: 'Comment on hgss-2024-6', Kristian Schlegel, 06 Jun 2024
As Topical Editor I strongly recommend to follow the suggestions 1 -3 of referee #2:
> larger fonts in the figures
> full names
> locations on a map
Citation: https://doi.org/10.5194/hgss-2024-6-EC1 - AC2: 'Reply on EC1', Jose Manuel Tordesillas, 19 Jun 2024
Status: closed
-
RC1: 'Comment on hgss-2024-6', Mioara Mandea, 23 May 2024
This manuscript presents a tour of measurements realised over Iberian Peninsula, with a focus on Royal Observatory of Madrid. The information are interesting and somehow unique. Nevertheless, I am in the inevitability to recommend a major revision of this manuscript. It has to be re-worked to attain an acceptable level for publication in HGSS.
Specific comments
- The paper structure needs to be revisited, with a clear introduction, a section dedicated to ROB where all information about it are gathered, a section on other Spanish observatories, a result session to show different comparisons between observatories and with models, before concluding.
- This manuscript invokes to provide an historical evolution of the geomagnetic declination at the Royal Observatory of Madrid. In describing the history it is needed to tell more about the first instruments (e.g. lines 74-77 – which kind of magnetometers of inclinometers, etc). Figure 5 shows an inclinometer, maybe some others photos can be provided?
- Many information are difficult to read. For example, in the section “Observatory data selection” I suggest the authors to draw a map with the used observatories. It would be nice to provide a table gathering the main information (observatory name, iaga code, coordinates, starting time - closing time, instruments, data availability - minutes, hourly, monthly, annual, etc).
- Some figures need to be revisited. E.g.
- In Figure 4 the comparison with the gufm1 model is presented, but this model is not built to describe variations on daily basis. Moreover, the difference is not du only to crustal field, but maybe to other factors, as unmodelled contributions or errors in measurements. To compute the crustal field (which can be considered constant in time) I suggest you to adapt methods proposed in the literature.
- Figures indicating series and comporting many plots may be view over the same time-span (min _ max of the series). This refers mainly to figures 7, 11.
- Coimbra observatory has a long series of observation. A comparison with the series published in 2021 (and not cited), can bring interesting information and discussions.
- The IGRF model is invoked (line 369), without citations. This choice is not very clear, and I wonder why not to use the gufm1 and COV-OBS models, only.
- The last session needs to be revisited, to get into some real discussions/ conclusions. The section on ROM observatories has to include the Table 1 and the Figure 16. At the end of the paper we would expected some interpretation of the observed secular variation curves.
Finally, efforts are needed to improve the English. Some parts are difficult to read: e.g. abbreviation used and not defined or defined after some pages, as IGN; “Declination data is translated from SPT to ROM » - data are not translated, they are adjusted; some expressions are not clear (“Note that the solar activity is not recorded before 1700 due to the scarce number of declination data”). I encourage the authors to work on the manuscript to provide a more fluid reading.
Some references:
Mandea, M. and Langlais, B. (2002) Observatory Crustal Magnetic Biases during MAGSAT and Oersted Satellite Missions. Geophysical Research Letters, 29.
Morozova, A. L., Ribeiro, P., and Pais, M. A.: Homogenization of the historical series from the Coimbra Magnetic Observatory, Portugal, Earth Syst. Sci. Data, 13, 809–825, https://doi.org/10.5194/essd-13-809-2021, 2021
Citation: https://doi.org/10.5194/hgss-2024-6-RC1 -
AC1: 'Reply on RC1', Jose Manuel Tordesillas, 29 May 2024
Many thanks to Dr. Mioara Mandea for the modifications suggested to improve the quality of our work.
We will review and revise the manuscript taking into account your suggestions.
In the coming days, we will upload a new version of the manuscript and a response letter answering to your comments.
Citation: https://doi.org/10.5194/hgss-2024-6-AC1 - AC4: 'Reply on RC1', Jose Manuel Tordesillas, 19 Jun 2024
-
RC2: 'Comment on hgss-2024-6', Tohru Araki, 31 May 2024
The contour line of zero geomagnetic declination always exists somewhere on the Earth's surface. The fact that it passes through a certain point at a certain time has no special physical meaning. On the other hand, it is meaningful to know when the geomagnetic declination becomes zero at a specific observation point that has played a historical role in measuring the geomagnetic field, because it adds new data to the geomagnetic record accumulated at that observation point.
The main objective of this paper is to determine the date and time of occurrence of zero declination at the Royal Madrid Observatory（RMO）, the first observatory in Spain to begin routine geomagnetic observations, and in relation to this, to summarize the distribution and temporal changes of declination in the Iberian Peninsula and its surrounding areas, as well as the history of the scattered observatories.
The structure of the paper is reasonable but there is room for improvement to make it easier for the casual reader to understand.
- The font on the diagrams is too small.
- The full names should be included in parentheses when their abbreviations appear at first.
- Locations of the observatories referred should be shown on the map. This could be included in Figure 8.
- Figure 4: The time variation is unclear. The vertical scale should be changed so that the variation is clearer.
- lines 24 and 31：What "Supplementary Material" do refer to?
- Lines 25-26: "that this observatory does not have a great tradition on geomagnetism"): What does this mean? Is RMO not important?
- Figure 2 : Zero declination horizontal line should be indicated.
- A brief explanation of the geomagnetic database (HISTMAG, gufmq1model), is necessary
- Is it possible to know the date and location of the first self-recording magnetometer observations?
Citation: https://doi.org/10.5194/hgss-2024-6-RC2 - AC3: 'Reply on RC2', Jose Manuel Tordesillas, 19 Jun 2024
-
EC1: 'Comment on hgss-2024-6', Kristian Schlegel, 06 Jun 2024
As Topical Editor I strongly recommend to follow the suggestions 1 -3 of referee #2:
> larger fonts in the figures
> full names
> locations on a map
Citation: https://doi.org/10.5194/hgss-2024-6-EC1 - AC2: 'Reply on EC1', Jose Manuel Tordesillas, 19 Jun 2024
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