the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 06 Dec 2022
Multiscale meteorological controls and impact of soil moisture heterogeneity on radiation fog in complex terrain
Abstract. Coupled surface-atmosphere high-resolution simulations were carried out to understand radiation fog development and persistence in a city surrounded by complex terrain. The controls of mesoscale meteorology and microscale soil moisture heterogeneity on fog were investigated using case studies for the city of Christchurch, New Zealand. Numerical model simulations from the synoptic to micro- scale were carried out using the Weather Research and Forecasting (WRF) model and the Parallelised Large-Eddy Simulation Model (PALM). Heterogeneous soil moisture, land use, and topography were included. The spatial heterogeneity of soil moisture was derived using Landsat 8 (https://www.usgs.gov/landsat-missions/landsat-8, last access: 10 October 2022) satellite imagery and ground-based meteorological observations. Eight simulations were carried out under identical meteorological conditions. One contained homogeneous soil moisture and one contained heterogeneous soil moisture derived from Landsat 8 imagery. For the other six simulations, the soil moisture heterogeneity magnitudes were amplified following the observed spatial distribution to aid our understanding of the impact of soil moisture heterogeneity. Our results showed that soil moisture heterogeneity did not significantly change the general spatial structure of near-surface fog occurrence, even when amplified. However, compared to homogeneous soil moisture, spatial heterogeneity in soil moisture leads to significant changes in radiation fog duration. The resulting changes in fog duration can be more than 50 minutes, although such changes are not directly correlated with spatial variations in soil moisture. The simulations showed that the mesoscale (104 to 2 × 105 m) meteorology controls the location of fog occurrence, while soil moisture heterogeneity alters fog duration at the microscale (10−2 to 103 m). Our results highlight the importance of including soil moisture heterogeneity for accurate spatiotemporal fog forecasting.
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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.
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- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
- RC1: 'Comment on egusphere-2022-1229', Stephanie Westerhuis, 10 Jan 2023
-
RC2: 'Comment on egusphere-2022-1229', Anonymous Referee #2, 01 Feb 2023
Review of https://doi.org/10.5194/egusphere-2022-1229 : «Multiscale meteorological controls and impact of soil moisture heterogeneity on radiation fog in complex terrain” by Lin et al., submitted to EGUsphere
Recommendation : Rejected
This work proposes a modelling study on a radiation fog case around Christchurch to investigate first the mechanisms leading to spatial heterogeneities of the fog life cycle and then the impact of soil moisture heterogeneity. The fog simulations are conducted with the PALM LES model already used for fog studies. The first part analyzes the spatial variability of fog duration, near-surface visibility, water vapour and modified Richardson number as an indicator of stability for the study case. The second part deals with a range of spatially heterogeneous soil moisture conditions in order to assess the impact of soil moisture on radiation fog duration.
The topic is very interesting, the objectives are relevant and promising (the introduction is very well written and promising), but the results are very disappointing with an incomplete analysis, and do not present any progress on the topic.
My major concerns are that:
- The numerical choices on the model configuration are not always clearly presented, and are sometimes debatable (see more details below). This does not give confidence in the quality of the results.
- The first part of the results concerning the meteorological controls is confusing, explanations are difficult to understand in relation to the geography of the maps, and we do not understand the results that emerge. I really found the 4.1 part very difficult to read: it is not always clear which part of the map is commented on.
- The conclusion of this part is that the macrostructure of fog occurrence and distribution is highly controlled by topography and the mesoscale meteorology: although we are not very surprised by this conclusion, it is a bit hasty and we do not learn much.
- There is no comparison to observations, which would allow to know if the simulations are relevant and can be considered as reliable. We understand that authors do not attempt to replicate a real radiation fog event in the simulations. But a direct comparison of the simulation to the observations presented in A1 would have been beneficial to give confidence in the simulations, as well as a comparison of cloud fraction or cloud water content to satellite images.
- For the second part of the results concerning different soil moisture conditions, the test only focuses on the magnitude of soil moisture heterogeneity. But a preliminary test would be necessary, dealing with the sensitivity to the soil moisture itself.
- Results concerning soil moisture heterogeneity do not show a clear impact on the fog duration. Indeed, the authors first underline that “there is no direct evidence to link the changes in soil moisture to the changes in fog duration” but just after they conclude that fog duration is sensitive to changes in soil moisture heterogeneity at microscale: here again, this is not really acceptable.
- The presented fields are rather poor compared to the potential of diagnostics classically available in a LES (vertical temporal evolution, budgets ...). For instance, the fog life cycle is only represented through fog duration 2D maps, without separating initiation and dissipation times.
- In the same way, the paper deals with the impact of soil moisture, but no surface heat flux is presented.
To summarize, I would say that the objectives of the paper are very interesting, but the results and the analysis are not up to the objectives. For a new submission, it would be necessary to produce new fields and diagnostics, and to analyze more deeply the processes driving the fog life cycle and the spatial heterogeneities, and the role of soil humidity.
Model configuration :
The choices of simulation configuration are not clearly enough presented and argued, with sometimes questionable choices:
- It seems that the first vertical level is at 18 m height: it is not suitable at all to fog simulations as we know the necessity to have a first level very close to the ground (max 2 m) (see Tardif, 2007)
- The initialisation of PALM mixes observed atmospheric vertical profiles (for U, V, q) and simulated ones (for rv) from WRF: are they consistent? In other words, are the WRF simulated U, V, q profiles close to the observed ones?
- I suppose that D01 is used without orography for the cyclic boundary conditions: this should be indicated.
- what turbulence scheme is used ? What are its characteristics (order of closure, mixing length, 3D or 1D …) ?
- why is the microphysical scheme off in D02 and D03? Is it a way to prevent cloud advection from D02 to D03 ?
- for the Kessler scheme, what constant value is used for droplet concentration ? Is there droplet settling and if yes, how is it implemented ? Is there droplet deposition ?
References:
Tardif, R. (2007). The impact of vertical resolution in the explicit numerical forecasting of radiation fog: A case study. Pure and Applied Geophysics, 164, 1221-1240.
Citation: https://doi.org/10.5194/egusphere-2022-1229-RC2 -
EC1: 'Comment from co-editor on egusphere-2022-1229', Heini Wernli, 03 Feb 2023
Dear Dr. Lin
As you have seen, you received two very thoughtful, constructive, but also critical reviews of your paper. While both reviewers regard the topic and general approach as interesting and promising, they both conclude that, in its present form, the analysis of the results is incomplete and does not support some of the main statements made in the abstract and conclusions. Also, parts of the paper seem to be distracting (touching on themes that are not relevant for the study), while other parts are too short, including the explanation of the simulation setup and the analysis of the physical processes in the model simulations. One reviewer suggests major revisions and the other to reject the paper in its current form. First of all, I invite you to submit detailed final author comments where you can reply to the points raised by the reviewers.
You can then decide whether you prefer to withdraw the paper, take your time to do more in-depth analyses and submit the revised version as a new submission (to ACP or an other journal), or whether you prefer to stay in the loop and continue the review process with a strongly revised version. In any case, a more detailed analysis of the modelled processes will be required for a much better understanding of the fog event, and it would be necessary to produce new diagnostics to analyze more deeply the processes driving the fog life cycle and the spatial heterogeneities, and the role of soil humidity.
With best regards,
Heini WernliCitation: https://doi.org/10.5194/egusphere-2022-1229-EC1 - AC1: 'Authors' response to reviewers on egusphere-2022-1229', Dongqi Lin, 24 Mar 2023
Interactive discussion
Status: closed
- RC1: 'Comment on egusphere-2022-1229', Stephanie Westerhuis, 10 Jan 2023
-
RC2: 'Comment on egusphere-2022-1229', Anonymous Referee #2, 01 Feb 2023
Review of https://doi.org/10.5194/egusphere-2022-1229 : «Multiscale meteorological controls and impact of soil moisture heterogeneity on radiation fog in complex terrain” by Lin et al., submitted to EGUsphere
Recommendation : Rejected
This work proposes a modelling study on a radiation fog case around Christchurch to investigate first the mechanisms leading to spatial heterogeneities of the fog life cycle and then the impact of soil moisture heterogeneity. The fog simulations are conducted with the PALM LES model already used for fog studies. The first part analyzes the spatial variability of fog duration, near-surface visibility, water vapour and modified Richardson number as an indicator of stability for the study case. The second part deals with a range of spatially heterogeneous soil moisture conditions in order to assess the impact of soil moisture on radiation fog duration.
The topic is very interesting, the objectives are relevant and promising (the introduction is very well written and promising), but the results are very disappointing with an incomplete analysis, and do not present any progress on the topic.
My major concerns are that:
- The numerical choices on the model configuration are not always clearly presented, and are sometimes debatable (see more details below). This does not give confidence in the quality of the results.
- The first part of the results concerning the meteorological controls is confusing, explanations are difficult to understand in relation to the geography of the maps, and we do not understand the results that emerge. I really found the 4.1 part very difficult to read: it is not always clear which part of the map is commented on.
- The conclusion of this part is that the macrostructure of fog occurrence and distribution is highly controlled by topography and the mesoscale meteorology: although we are not very surprised by this conclusion, it is a bit hasty and we do not learn much.
- There is no comparison to observations, which would allow to know if the simulations are relevant and can be considered as reliable. We understand that authors do not attempt to replicate a real radiation fog event in the simulations. But a direct comparison of the simulation to the observations presented in A1 would have been beneficial to give confidence in the simulations, as well as a comparison of cloud fraction or cloud water content to satellite images.
- For the second part of the results concerning different soil moisture conditions, the test only focuses on the magnitude of soil moisture heterogeneity. But a preliminary test would be necessary, dealing with the sensitivity to the soil moisture itself.
- Results concerning soil moisture heterogeneity do not show a clear impact on the fog duration. Indeed, the authors first underline that “there is no direct evidence to link the changes in soil moisture to the changes in fog duration” but just after they conclude that fog duration is sensitive to changes in soil moisture heterogeneity at microscale: here again, this is not really acceptable.
- The presented fields are rather poor compared to the potential of diagnostics classically available in a LES (vertical temporal evolution, budgets ...). For instance, the fog life cycle is only represented through fog duration 2D maps, without separating initiation and dissipation times.
- In the same way, the paper deals with the impact of soil moisture, but no surface heat flux is presented.
To summarize, I would say that the objectives of the paper are very interesting, but the results and the analysis are not up to the objectives. For a new submission, it would be necessary to produce new fields and diagnostics, and to analyze more deeply the processes driving the fog life cycle and the spatial heterogeneities, and the role of soil humidity.
Model configuration :
The choices of simulation configuration are not clearly enough presented and argued, with sometimes questionable choices:
- It seems that the first vertical level is at 18 m height: it is not suitable at all to fog simulations as we know the necessity to have a first level very close to the ground (max 2 m) (see Tardif, 2007)
- The initialisation of PALM mixes observed atmospheric vertical profiles (for U, V, q) and simulated ones (for rv) from WRF: are they consistent? In other words, are the WRF simulated U, V, q profiles close to the observed ones?
- I suppose that D01 is used without orography for the cyclic boundary conditions: this should be indicated.
- what turbulence scheme is used ? What are its characteristics (order of closure, mixing length, 3D or 1D …) ?
- why is the microphysical scheme off in D02 and D03? Is it a way to prevent cloud advection from D02 to D03 ?
- for the Kessler scheme, what constant value is used for droplet concentration ? Is there droplet settling and if yes, how is it implemented ? Is there droplet deposition ?
References:
Tardif, R. (2007). The impact of vertical resolution in the explicit numerical forecasting of radiation fog: A case study. Pure and Applied Geophysics, 164, 1221-1240.
Citation: https://doi.org/10.5194/egusphere-2022-1229-RC2 -
EC1: 'Comment from co-editor on egusphere-2022-1229', Heini Wernli, 03 Feb 2023
Dear Dr. Lin
As you have seen, you received two very thoughtful, constructive, but also critical reviews of your paper. While both reviewers regard the topic and general approach as interesting and promising, they both conclude that, in its present form, the analysis of the results is incomplete and does not support some of the main statements made in the abstract and conclusions. Also, parts of the paper seem to be distracting (touching on themes that are not relevant for the study), while other parts are too short, including the explanation of the simulation setup and the analysis of the physical processes in the model simulations. One reviewer suggests major revisions and the other to reject the paper in its current form. First of all, I invite you to submit detailed final author comments where you can reply to the points raised by the reviewers.
You can then decide whether you prefer to withdraw the paper, take your time to do more in-depth analyses and submit the revised version as a new submission (to ACP or an other journal), or whether you prefer to stay in the loop and continue the review process with a strongly revised version. In any case, a more detailed analysis of the modelled processes will be required for a much better understanding of the fog event, and it would be necessary to produce new diagnostics to analyze more deeply the processes driving the fog life cycle and the spatial heterogeneities, and the role of soil humidity.
With best regards,
Heini WernliCitation: https://doi.org/10.5194/egusphere-2022-1229-EC1 - AC1: 'Authors' response to reviewers on egusphere-2022-1229', Dongqi Lin, 24 Mar 2023
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Marwan Katurji
Laura E. Revell
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Andrew Sturman
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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(29350 KB) - Metadata XML
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Supplement
(4742 KB) - BibTeX
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- Final revised paper