the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 13 May 2024
Assessing Soil and Potential Air Temperature Coupling Using PALM-4U: Implications for Idealized Scenarios
Abstract. Underground heat extremes amplified by e.g., underground infrastructure or badly adjusted geothermal systems have long been discussed in geosciences. However, there is little emphasis on the exchange between these subsurface heat extremes and the atmosphere. To address the issue, this study investigates the impact of varying soil temperatures on potential air temperatures in an idealized domain using the turbulence and building resolving large eddy simulation urban micro-climate model PALM-4U. This involves two steps: first we test if and how idealized domains can be simulated, second the coupling between surface and subsurface energy fluxes or rather temperatures in air and soil are in focus. We develop several scenarios, distinguishing between cyclic or Dirichlet/radiation boundary conditions along the x-axis, between summer and winter, as well as between various land cover types. Our results demonstrate that cyclic boundary conditions induce modifications of the potential air temperatures due to changes in the soil temperature. The magnitude of the impact varies with respect to the tested land covers, which primarily affect absolute temperatures. Daytime and season have a larger influence on the magnitude of the modifications. A 5 K increase in subsurface temperatures at 2 m depth results in a maximum of a 0.38 K increase for near surface potential air temperatures in winter between 09:00 and 10:00 local time after three days of simulation. When soil temperatures are decreased, we find predominantly inverse patterns. The least influence is found during summer at 09:00 local time where the elevated soil temperatures increase potential air temperatures by only 0.02 K over short- and tall grass, and 0.18 K over bare soil. When using Dirichlet/radiation boundary conditions, the atmosphere cannot develop freely and changing soil temperatures do not impact potential air temperatures.
These results help to enhance our understanding of the coupling between soil- and atmospheric temperatures and also provide recommendations for the simulability of idealized but reality-oriented scenarios in PALM-4U. It is one of the first studies that demonstrates that heat and cold sources in the soil can affect atmospheric parameters.
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Status: closed
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RC1: 'Comment on egusphere-2024-1234', Anonymous Referee #1, 02 Jul 2024
Please see my comments in the attached file.
- AC2: 'Reply on RC1', Patricia Glocke, 13 Aug 2024
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RC2: 'Comment on egusphere-2024-1234', Anonymous Referee #2, 13 Jul 2024
In their article titled “Assessing Soil and Potential Air Temperature Coupling Using PALM-4U: Implications for Idealized Scenarios,” the authors aim to answer the important question of how underground temperature extremes impact atmospheric temperatures. More specifically, the authors formulate the following three research questions:
- How to depict a realistic but idealized domain in PALM-4U?
- Do heat or cold extremes in the soil modify potential air temperatures?
- What parameters affect these modifications?
The authors are moving in a new direction by investigating the effect of subsurface temperature extremes on air temperatures (and not vice-versa). In the introduction, the authors succinctly address the relevance of this novel perspective. With its interdisciplinary view of the interactions between multiple spheres of the Earth system, this research is of interest to the scientific community and beyond, making it a suitable contribution to ESD. The authors present a well-written and concise manuscript in most parts and provide a good introduction to the general relevance of the topic as well as typical approaches and limitations in understanding and implementing a thermal coupling of the subsurface and the atmosphere.
However, I find the manuscript difficult to follow for the following reasons: First, the introduction provides a good overview of the relevance and state of knowledge, but it seems decoupled from the rest of the manuscript. For example, I assume the choice of boundary conditions is self-evident to the authors, but it may not be to every interested reader. In that way, a brief explanation of boundary conditions used in temperature simulation at interfaces (e.g., in atmospheric research) would help the reader understand the choice of boundary conditions, their pros and cons, and why they were considered for the investigation.
Second, there is a very detailed presentation/explanation and interpretation (rather than discussion) of the obtained results. My impression is that the authors focus on these highly detailed results, but the general evaluation of the model performance/suitability is not prominently discussed and/or limited to the plausibility check of the results. Therefore, the question arises of how the results and model performance can be evaluated and checked. Can available datasets or data from experiments be used to validate the results?
The very technical nature and a high degree of detailed explanation of the results make it difficult to follow the common theme and line of argumentation and really understand the work's contribution and novelty – also regarding the accuracy of the results and validity beyond the model domain. The guidance of the reader is missing or at least not apparent to me. Hence, I encourage the authors to revise the manuscript accordingly (moderate to major revision required).
Minor comments include:
Lines 20-27: Check the syntax for suitability in a scientific journal
Line 41: How relevant is the impact of an individual construction? The accumulation is probably relevant, and the examples given appear somewhat random.
Line 46: Delete “However”
Line 64: Please specify “near surface atmosphere”
Line 87: What about heat transport via percolating water? Should be addressed.
Line 158 and others: Is “right side” the best terminology to refer to the orientation in the model?
Line 197: You mention Fig. 2 and then Fig.5. Should Fig. 5 then be renamed as Fig. 3?
Citation: https://doi.org/10.5194/egusphere-2024-1234-RC2 - AC1: 'Reply on RC2', Patricia Glocke, 13 Aug 2024
Status: closed
-
RC1: 'Comment on egusphere-2024-1234', Anonymous Referee #1, 02 Jul 2024
Please see my comments in the attached file.
- AC2: 'Reply on RC1', Patricia Glocke, 13 Aug 2024
-
RC2: 'Comment on egusphere-2024-1234', Anonymous Referee #2, 13 Jul 2024
In their article titled “Assessing Soil and Potential Air Temperature Coupling Using PALM-4U: Implications for Idealized Scenarios,” the authors aim to answer the important question of how underground temperature extremes impact atmospheric temperatures. More specifically, the authors formulate the following three research questions:
- How to depict a realistic but idealized domain in PALM-4U?
- Do heat or cold extremes in the soil modify potential air temperatures?
- What parameters affect these modifications?
The authors are moving in a new direction by investigating the effect of subsurface temperature extremes on air temperatures (and not vice-versa). In the introduction, the authors succinctly address the relevance of this novel perspective. With its interdisciplinary view of the interactions between multiple spheres of the Earth system, this research is of interest to the scientific community and beyond, making it a suitable contribution to ESD. The authors present a well-written and concise manuscript in most parts and provide a good introduction to the general relevance of the topic as well as typical approaches and limitations in understanding and implementing a thermal coupling of the subsurface and the atmosphere.
However, I find the manuscript difficult to follow for the following reasons: First, the introduction provides a good overview of the relevance and state of knowledge, but it seems decoupled from the rest of the manuscript. For example, I assume the choice of boundary conditions is self-evident to the authors, but it may not be to every interested reader. In that way, a brief explanation of boundary conditions used in temperature simulation at interfaces (e.g., in atmospheric research) would help the reader understand the choice of boundary conditions, their pros and cons, and why they were considered for the investigation.
Second, there is a very detailed presentation/explanation and interpretation (rather than discussion) of the obtained results. My impression is that the authors focus on these highly detailed results, but the general evaluation of the model performance/suitability is not prominently discussed and/or limited to the plausibility check of the results. Therefore, the question arises of how the results and model performance can be evaluated and checked. Can available datasets or data from experiments be used to validate the results?
The very technical nature and a high degree of detailed explanation of the results make it difficult to follow the common theme and line of argumentation and really understand the work's contribution and novelty – also regarding the accuracy of the results and validity beyond the model domain. The guidance of the reader is missing or at least not apparent to me. Hence, I encourage the authors to revise the manuscript accordingly (moderate to major revision required).
Minor comments include:
Lines 20-27: Check the syntax for suitability in a scientific journal
Line 41: How relevant is the impact of an individual construction? The accumulation is probably relevant, and the examples given appear somewhat random.
Line 46: Delete “However”
Line 64: Please specify “near surface atmosphere”
Line 87: What about heat transport via percolating water? Should be addressed.
Line 158 and others: Is “right side” the best terminology to refer to the orientation in the model?
Line 197: You mention Fig. 2 and then Fig.5. Should Fig. 5 then be renamed as Fig. 3?
Citation: https://doi.org/10.5194/egusphere-2024-1234-RC2 - AC1: 'Reply on RC2', Patricia Glocke, 13 Aug 2024
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