the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 05 May 2025
Evaporation measurements using commercial microwave links as scintillometers
Abstract. As the spatial coverage of evaporation observations is limited, we propose a novel, opportunistic method to estimate evaporation in which we consider commercial microwave links (CMLs), such as used in cellular telecommunication networks, in combination with scintillometry. Scintillometers are dedicated instruments to measure path-integrated latent and sensible heat fluxes, transmitting electromagnetic radiation that is diffracted by turbulent eddies between transmitter and receiver, causing the so-called scintillation effect. CMLs are line-of-sight devices that transmit electromagnetic radiation at similar frequencies as microwave scintillometers. However, CMLs and their sampling strategies are designed to ensure a continuously functioning wireless communication network rather than to capture the scintillation effect. Here, we estimate 30-min latent heat fluxes and daily evaporation using a former CML. To do so, we use data of a 38 GHz Nokia CML (formerly part of a telecom network) installed over an 856 m path at the Ruisdael Observatory near Cabauw, the Netherlands. We compare our results with estimates from an optical and microwave scintillometer setup, as well as an EC system. To obtain the flux estimates using the CML, we apply the two-wavelength method, in combination with the optical scintillometer, as well as a standalone energy-balance method (EBM), requiring net radiation estimates. For comparison, we also consider the free-convection limit of Monin-Obukhov similarity theory (MOST), instead of the complete scaling. An advantage of this approach is that it does not require horizontal wind speed measurements, which are more difficult to obtain in complex environments. For the net radiation estimates, we use in-situ measured radiation and data products provided by the Satellite Application Facility on Land Surface Analysis (LSA SAF) of EUMETSAT. Considering both turbulent heat fluxes, the two-wavelength method outperforms the EBM. The standalone EBM shows a reasonable performance, but also a large dependence on the quality of the net radiation estimates. When aggregating our 30-min latent heat fluxes to daily evaporation estimates, the relative performance of the methods remains comparable to that at 30-min intervals. These daily evaporation estimates could also be useful for catchment hydrological applications. Application of the free-convection scaling instead of the complete MOST scaling results in a comparable performance for all methods.
Competing interests: Miriam Coenders-Gerrits is a member of the editorial board of Hydrology and Earth System Sciences.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.-
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
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- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2025-1128', Prajwal Khanal, 02 Jun 2025
- AC1: 'Reply on RC1', Luuk van der Valk, 04 Jul 2025
-
RC2: 'Comment on egusphere-2025-1128', Anonymous Referee #2, 06 Jun 2025
See attached PDF. I think the study is worth publishing but the article needs some massaging to be more reader friendly.
- AC2: 'Reply on RC2', Luuk van der Valk, 04 Jul 2025
-
RC3: 'Comment on egusphere-2025-1128', Anonymous Referee #3, 26 Jun 2025
Review: Evaporation measurements using commercial microwave links as scintillometers.
General summary of review:
The paper discusses/demonstrates the use of commercial microwave links as scintillometers, which is a very important and interesting topic. In a previous aper the authors discussed and demonstrated the use of such microwave links for determining the structure parameter of the refractive index, Cnn (the base for determining turbulent flux estimates from scintillations). For operational evaporation estimates either a combination with an optical scintillometer or a restriction on available energy is required (assuming energy closure), both of which are examined in the current paper. Despite claiming that the results using commercial microwave links with an optical scintillometer are comparable to “reference” observations, this does not hold. Results worsen up to a factor 2.5 compared to a designated dual scintillometer set-up versus EC observations. Results with the available energy-approach seem slightly better, but sensible heat fluxes deteriorate. Further restriction by neglecting shear-driven turbulence improves the performance, but for the wrong reasons (as correctly stated by the authors). Despite these seemingly not very positive results the story is worth publishing, but need further clarifications and a more clear structure/story telling.
English is good, although at a few points sentences are a bit lengthy and it would be better to split them into two or three shorter sentences.
In general sections 1 up and until 3 are OK, but section 4 is written in a rather chaotic manner, jumping between (too) many different approaches making it very hard to understand what is meant exactly. In addition the abbreviations used are not consistent throughout the section/paper. Sections 5 and 6 seem more a bit of a repetition of section 4 than that they are “Discussion” and “Conclusion” sections.
Over-all, the paper needs major revisions before publishing.
This review summary is exemplified by several, but not exhaustive, examples below.
Details/Examples:
Line 26: “Bastiaanssen et.al. 1998, Mu et.al., 2007” more recent references, as well as overview papers, could have been used here to illustrate the point the authors make.
Line 52: “so that the Cnn values are overestimated”; better to replace this with: “resulting in an overestimation of Cnn values”.
Lines 54-57: Please split up this sentence to make it more clear.
Line 91: “to be 0.8”; maybe add that this is for daytime conditions.
Line 127: “To do so, closure of the measured energy balance is assumed” It might be good to mention at this point that closure of the energy balance is almost never accomplished, especially not in “complex measurement environments (e.g. forests or cities)”.
Line 162: “from 1 April 2024 to 1 October 2024”; please mention that only daytime data is used.
Lines 164-165: “The footprints … included.” It might be considered to show the typical footprint in Figure 2 to illustrate this statement.
Line 169: Replace “we show” by “it is shown”, since the authors are not (exactly) the same.
Line 171: add “a” between “is” and “more”.
Lines 184-186: “In order … time intervals”. Please rephrase this to make clear what exactly has been done here.
Line 206: “comparable”; unclear to what; please add clarification.
Line 222: “the expected differences”; please explain what these expected differences are.
Lines 231: “In this…versus the MWS-2λ.” Please use shorter sentence to make this more clear.
Lines 233-234: “This Bowen … intervals).” Please explain/justify why this was done (instead of using the actual Bowen ratio).
Line 237-238, figure 5, caption: remove “together”
Line 237-238, figure 6, caption “The used Bowen ….intervals).” Please explain why this constant ratio is used instead of the (more appropriate?) instantaneous/daily value.
Line 238 and further; please use the same abbreviation throughout the paper (for example not EBM without addition versus later on EBM-LSA and/or EBM-ßEC). Maybe a good idea would be to add an abbreviation list at the start/end of the paper for more easy reference.
Line 241: add “it” between “but” and “has”.
Lines 243-245. This sentence is insufficient explanation at this point. Only mentioning the Van der Valk 2025 paper is not enough; one or two additional explanatory lines would be required here.
Line 246-248. “If desired… and H.” Doing so would be rather arbitrary and considered finetuning, which is not a good approach to solve this particular phenomenon.
Line 256: “two alternative methods”; unclear what is meant with these two alternative methods. Please explain.
Line 259: “between between”; remove one of these.
Line 259: “estimates directly obtained from LSA SAF”; unclear what is meant here. Please explain.
Lines 218-261: In this section too many methods are intercompared to each other, where the assessment is based on three different parameters (MBE, IQR, r). Apart from the fact that it is difficult to read a piece of text with numerous abbreviations also the comparison is described by means of jumping between approaches and also between assessment parameters. This needs to be described in a much more systematic manner. It is advised to use consistent acronyms, split the section into subsections where performance versus the reference method’s (only) are described w.r.t. MBE, IQR and r. Preferably only one reference method (which is the EC observation) should be used.
Lines 277-278: “the performance…is roughly comparable”: This is an incorrect statement. The r are lower in all four cases and the MBE and IQR are up to a factor 2.6 higher!
Line 282: Add “an” before “CML”
Lines 282-289: This section is mainly a repetition of what is described already in section 4.
Lines 293-294: “This underlines …the MBE” This statement is correctly mentioning that the method is suffering from an in-accurate product (Rn) that provides the upper limit of the turbulent fluxes. Because of this, a discussion on the accuracy of the relative contribution of H and LE to Rn would be more beneficial here. This would also better fit the topic of the paper, namely determination of turbulent LE flux.
Lines 304-306: “Moreover…estimates”. These lines are very confusing, please rephrase.
Line 310: “These two”, unclear what is meant with “these two”, please add an explanation (e.g. variables/parameters?).
Lines 316-319. Please describe/demonstrate why this (i.e. increase in LE and reduction of H due to free convection assumption) occurs instead of saying that this occurs.
Line 323: “The former”; unclear what is meant with “The former”, please explain.
Line 346: please remove “so that Cnn estimates….et.al. 2015b).”
Line 350: “shows” should be replaced by “show”
Lines 349-356: Indeed as mentioned also previously w.r.t. line 127; the energy balance or closure does not hold everywhere, in fact almost nowhere, and especially not over complex terrain (cities and forests). Agani, this is more a discussion on the energy balance approach than on the proper functioning of CMLs for LE estimates. It would be nice/better if the discussion section would focus more on the CML method itself.
Lines 361-364: Not clear what is meant with this section, please add clarification, or remove.
Lines 370-371: Performance is roughly comparable to the reference; this is not true, see also remarks made w.r.t. lines 277-278.
Lines 380-382: “Yet, for … of the CML”: It is unclear why this statement would illustrate the added value of the CML. Please explain.
Line 397: “In general, …scintillometers” In fact this was already illustrated in the Van der Valk et.al. 2025 paper. To my opinion, in the current paper it is illustrated that operational scintillometry for LE estimates is not (yet?) possible with CMLs with a sufficient accuracy and that attempts to increase the accuracy are either hampered by inaccurate restriction/limitation determination or result in deteriorating sensible heat flux estimates. This in itself is a useful story to tell, though maybe less satisfying.
Citation: https://doi.org/10.5194/egusphere-2025-1128-RC3 - AC3: 'Reply on RC3', Luuk van der Valk, 04 Jul 2025
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2025-1128', Prajwal Khanal, 02 Jun 2025
Hi,
Please find my comments in the pdf attached.
Prajwal
- AC1: 'Reply on RC1', Luuk van der Valk, 04 Jul 2025
-
RC2: 'Comment on egusphere-2025-1128', Anonymous Referee #2, 06 Jun 2025
See attached PDF. I think the study is worth publishing but the article needs some massaging to be more reader friendly.
- AC2: 'Reply on RC2', Luuk van der Valk, 04 Jul 2025
-
RC3: 'Comment on egusphere-2025-1128', Anonymous Referee #3, 26 Jun 2025
Review: Evaporation measurements using commercial microwave links as scintillometers.
General summary of review:
The paper discusses/demonstrates the use of commercial microwave links as scintillometers, which is a very important and interesting topic. In a previous aper the authors discussed and demonstrated the use of such microwave links for determining the structure parameter of the refractive index, Cnn (the base for determining turbulent flux estimates from scintillations). For operational evaporation estimates either a combination with an optical scintillometer or a restriction on available energy is required (assuming energy closure), both of which are examined in the current paper. Despite claiming that the results using commercial microwave links with an optical scintillometer are comparable to “reference” observations, this does not hold. Results worsen up to a factor 2.5 compared to a designated dual scintillometer set-up versus EC observations. Results with the available energy-approach seem slightly better, but sensible heat fluxes deteriorate. Further restriction by neglecting shear-driven turbulence improves the performance, but for the wrong reasons (as correctly stated by the authors). Despite these seemingly not very positive results the story is worth publishing, but need further clarifications and a more clear structure/story telling.
English is good, although at a few points sentences are a bit lengthy and it would be better to split them into two or three shorter sentences.
In general sections 1 up and until 3 are OK, but section 4 is written in a rather chaotic manner, jumping between (too) many different approaches making it very hard to understand what is meant exactly. In addition the abbreviations used are not consistent throughout the section/paper. Sections 5 and 6 seem more a bit of a repetition of section 4 than that they are “Discussion” and “Conclusion” sections.
Over-all, the paper needs major revisions before publishing.
This review summary is exemplified by several, but not exhaustive, examples below.
Details/Examples:
Line 26: “Bastiaanssen et.al. 1998, Mu et.al., 2007” more recent references, as well as overview papers, could have been used here to illustrate the point the authors make.
Line 52: “so that the Cnn values are overestimated”; better to replace this with: “resulting in an overestimation of Cnn values”.
Lines 54-57: Please split up this sentence to make it more clear.
Line 91: “to be 0.8”; maybe add that this is for daytime conditions.
Line 127: “To do so, closure of the measured energy balance is assumed” It might be good to mention at this point that closure of the energy balance is almost never accomplished, especially not in “complex measurement environments (e.g. forests or cities)”.
Line 162: “from 1 April 2024 to 1 October 2024”; please mention that only daytime data is used.
Lines 164-165: “The footprints … included.” It might be considered to show the typical footprint in Figure 2 to illustrate this statement.
Line 169: Replace “we show” by “it is shown”, since the authors are not (exactly) the same.
Line 171: add “a” between “is” and “more”.
Lines 184-186: “In order … time intervals”. Please rephrase this to make clear what exactly has been done here.
Line 206: “comparable”; unclear to what; please add clarification.
Line 222: “the expected differences”; please explain what these expected differences are.
Lines 231: “In this…versus the MWS-2λ.” Please use shorter sentence to make this more clear.
Lines 233-234: “This Bowen … intervals).” Please explain/justify why this was done (instead of using the actual Bowen ratio).
Line 237-238, figure 5, caption: remove “together”
Line 237-238, figure 6, caption “The used Bowen ….intervals).” Please explain why this constant ratio is used instead of the (more appropriate?) instantaneous/daily value.
Line 238 and further; please use the same abbreviation throughout the paper (for example not EBM without addition versus later on EBM-LSA and/or EBM-ßEC). Maybe a good idea would be to add an abbreviation list at the start/end of the paper for more easy reference.
Line 241: add “it” between “but” and “has”.
Lines 243-245. This sentence is insufficient explanation at this point. Only mentioning the Van der Valk 2025 paper is not enough; one or two additional explanatory lines would be required here.
Line 246-248. “If desired… and H.” Doing so would be rather arbitrary and considered finetuning, which is not a good approach to solve this particular phenomenon.
Line 256: “two alternative methods”; unclear what is meant with these two alternative methods. Please explain.
Line 259: “between between”; remove one of these.
Line 259: “estimates directly obtained from LSA SAF”; unclear what is meant here. Please explain.
Lines 218-261: In this section too many methods are intercompared to each other, where the assessment is based on three different parameters (MBE, IQR, r). Apart from the fact that it is difficult to read a piece of text with numerous abbreviations also the comparison is described by means of jumping between approaches and also between assessment parameters. This needs to be described in a much more systematic manner. It is advised to use consistent acronyms, split the section into subsections where performance versus the reference method’s (only) are described w.r.t. MBE, IQR and r. Preferably only one reference method (which is the EC observation) should be used.
Lines 277-278: “the performance…is roughly comparable”: This is an incorrect statement. The r are lower in all four cases and the MBE and IQR are up to a factor 2.6 higher!
Line 282: Add “an” before “CML”
Lines 282-289: This section is mainly a repetition of what is described already in section 4.
Lines 293-294: “This underlines …the MBE” This statement is correctly mentioning that the method is suffering from an in-accurate product (Rn) that provides the upper limit of the turbulent fluxes. Because of this, a discussion on the accuracy of the relative contribution of H and LE to Rn would be more beneficial here. This would also better fit the topic of the paper, namely determination of turbulent LE flux.
Lines 304-306: “Moreover…estimates”. These lines are very confusing, please rephrase.
Line 310: “These two”, unclear what is meant with “these two”, please add an explanation (e.g. variables/parameters?).
Lines 316-319. Please describe/demonstrate why this (i.e. increase in LE and reduction of H due to free convection assumption) occurs instead of saying that this occurs.
Line 323: “The former”; unclear what is meant with “The former”, please explain.
Line 346: please remove “so that Cnn estimates….et.al. 2015b).”
Line 350: “shows” should be replaced by “show”
Lines 349-356: Indeed as mentioned also previously w.r.t. line 127; the energy balance or closure does not hold everywhere, in fact almost nowhere, and especially not over complex terrain (cities and forests). Agani, this is more a discussion on the energy balance approach than on the proper functioning of CMLs for LE estimates. It would be nice/better if the discussion section would focus more on the CML method itself.
Lines 361-364: Not clear what is meant with this section, please add clarification, or remove.
Lines 370-371: Performance is roughly comparable to the reference; this is not true, see also remarks made w.r.t. lines 277-278.
Lines 380-382: “Yet, for … of the CML”: It is unclear why this statement would illustrate the added value of the CML. Please explain.
Line 397: “In general, …scintillometers” In fact this was already illustrated in the Van der Valk et.al. 2025 paper. To my opinion, in the current paper it is illustrated that operational scintillometry for LE estimates is not (yet?) possible with CMLs with a sufficient accuracy and that attempts to increase the accuracy are either hampered by inaccurate restriction/limitation determination or result in deteriorating sensible heat flux estimates. This in itself is a useful story to tell, though maybe less satisfying.
Citation: https://doi.org/10.5194/egusphere-2025-1128-RC3 - AC3: 'Reply on RC3', Luuk van der Valk, 04 Jul 2025
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Luuk D. van der Valk
Oscar K. Hartogensis
Miriam Coenders-Gerrits
Rolf W. Hut
Remko Uijlenhoet
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(3946 KB) - Metadata XML
-
Supplement
(9609 KB) - BibTeX
- EndNote
- Final revised paper
Hi,
Please find my comments in the pdf attached.
Prajwal