the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 23 Aug 2022
Temperature and CCN sensitivity of orographic precipitation enhanced by a mixed-phase seeder-feeder mechanism
Julia Thomas
Andrew Barrett
Abstract. Orographic precipitation is a key driver of flooding in mountainous areas. This article investigates the microphysical response of orographic rainfall to perturbations of temperature and cloud condensation nuclei (CCN) concentration. The study is motivated by the increased water vapour capacity of the atmosphere in a warming climate and the increasing frequency of extreme rainfall events. A case study for the Cumbria flood in December 2015 is performed with sensitivities using a realization of the `piggybacking' method implemented into a limited-area setup of the ICON model. A 6 % K-1 enhancement of rainfall results for the highest altitudes, caused by a `mixed-phase seeder-feeder mechanism', i.e. the interplay of melting and accretion. Total 24 h rainfall is found to increase by only 2 % K-1, significantly less than the 7 % K-1 increase in atmospheric water vapour. A rain budget analysis reveals that the negative temperature sensitivity of the condensation ratio and the increase of rain evaporation dampen the rainfall enhancement. Decreasing the CCN concentration speeds up the microphysical processing, which leads to an increase in total rainfall. At low CCN concentration the rainfall sensitivity to temperature is systematically smaller. It is shown that the CCN and temperature sensitivities are to a large extent independent (with a ±3 % relative error) and additive.
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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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Preprint
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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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Journal article(s) based on this preprint
Julia Thomas et al.
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2022-740', Anonymous Referee #1, 26 Sep 2022
Review of the manuscript entitled: “Temperature and CCN sensitivity of orographic precipitation enhanced by a mixed-phase seeder-feeder mechanism”.
The manuscript discusses the microphysical response of orographic precipitation to perturbations of temperature and cloud condensation nuclei (CCN) concentration. The authors provide technically sound analysis. There are, however, some comments that need to be addressed.
The manuscript contains English writing problems and needs to be carefully edited.
The first sentence of the Abstract is irrelevant to the subject of the manuscript and is better to be replaced by another sentence.
In the abstract and elsewhere, please replace “orographic rainfall” with “orographic precipitation”
It is better to remove the following sentence in the abstract or move it to the Introduction Section to have enough space to discuss the obtained results: “The study is motivated by the increased water vapour capacity of the atmosphere in a warming climate and the increasing frequency of extreme rainfall events."
Line 5: write out the full words for “ICON”
The Introduction is much weaker than the other parts of the manuscript and could be substantially improved. For example, the first paragraph of the Introduction does not provide any important information about the topic of the manuscript. It is irrelevant and can be omitted. Another example is in Line 22 where appropriate references and more clarification are required for the dynamic, thermodynamic, and microphysical contributions to precipitation changes under global warming. The microphysical contribution to precipitation changes is well discussed, but at least a few sentences can be added to explain the thermodynamic and dynamic contributions, particularly because the thermodynamic contribution to precipitation change is the main subject of the manuscript. As discussed in http://dx.doi.org/10.1007/s10584-022-03316-z, the precipitation response to climate change is regulated by two basic mechanisms, which include the wet-get-wetter mechanism and the warmer-get-wetter, both of which are referred to as the thermodynamic mechanism, while circulation changes under the impact of global warming which lead to precipitation changes are referred to as the dynamic change of precipitation.
Line 29: replace “by constant” with “be constant”
Line 34: Replace “English West coast” with “British West coast”
Line 45-46. Total precipitation might reduce or slightly change under a higher CCN concentration, but please note that some evidence suggests that heavy precipitation might increase in a polluted environment. For example, see the following paper: http://dx.doi.org/10.1016/j.atmosres.2016.10.021. This needs to be discussed in the Introduction, particularly because the importance of extreme precipitation and the risk of flooding is emphasized in the first paragraph of the introduction.
Line 49-50: This sentence does not mean anything: Which effect dominates highly depends on the synoptic conditions (e.g. whether convection is involved) and on the mountain geometry.
Line 56: westward or eastward?
Line 93: write out the full words in the first use of “DWD”
Parameterization schemes that are used for the boundary layer, radiation, etc. should be mentioned in Section 2.1
Lines 152-155: Rephrase the sentence.
Fig.4: It is better to start the label bar with white color representing zero value. Instead of using kg m-2 for the unit of precipitation, please consider writing it as mm for this figure and the others, although the values do not change.
Line 198-201. It is expected that heavy precipitation experiences the highest increase in response to warming, while light precipitation experiences a slight change or even decrease. It is interesting to compare the obtained results with those of http://dx.doi.org/ 10.1002/met.1724. This paper is already cited in the Introduction, but here or in the discussion section you can compare your results with their results and discuss the reasons for such behavior. In this paper, it is noted that more hygroscopic aerosols in the atmosphere could potentially increase heavy precipitation but reduce light precipitation. The author argued that an ample influx of water vapour over the regions with heavy precipitation could contribute to an increase of heavy precipitation under a polluted atmosphere, while less efficient autoconversion processes and/or increased cloud-top evaporation may contribute to a decrease in light precipitation. Could the same reasons contribute to an increase in heavy precipitation and a decrease in light precipitation in response to warming in your study? Please clarify. Such discussions could improve the quality of the manuscript.
Line 282: remove “a” before “only”
Line 407: Replace “in climate change” with “under climate change”
Citation: https://doi.org/10.5194/egusphere-2022-740-RC1 -
RC2: 'Comment on egusphere-2022-740', Anonymous Referee #2, 29 Sep 2022
This manuscript describes be sensitivity of precipitation efficiency with increased temperature and CCN concentration. I find the manuscript mostly well written and organized. The conclusions are justified and I think this manuscript should be published after some minor revisions.
Page 1, line 21: Can you provide a citation for the statement: “If there were no changes in cloud dynamics and microphysics, the total precipitation would increase by the same rate as total vapour inflow”
Page 2, line 35: When I first read through the manuscript, I questioned why specifically the English West Coast was mentioned. Later, when learning that the location of the Cambria flood is at the English Coast, I realized the importance. However, the Cambria flood has so far only been mentioned in the Abstract (and not given a more general location (the English West Coast)). I think a description of the Cambria flood needs to come before the statement of “enhanced precipitation along the English West coast”, or this statement needs to be moved.
Page 3, line 56: I suggest rewording to: “At the English West Coast, moist air flows that is moving westward over the Atlantic are ….”
Page 3, line 64: I suggest rephrasing to: “Only then are low mountain ranges (up to 1 km height) sufficient to ……”
Page 3, line 71: How long did the flood last? From 5th December to?
Page 3, line 71 to 77: This is a nice description of the Cumbria Flood and its area. I finally understand why the English West Coast is mentioned earlier. As mentioned in comment above, some description of the Cumbria Flood (at least location) needs to come before describing precipitation on the English West Coast so the reader understands why there is a focus on the English West coast.
Page 5, line 96: The triangular cells. This is the first time triangular cells are mentioned. Perhaps add a sentence how the grids are used in ICON.
Page 5, lines 112-114: On line 112 it is mentioned four sets of all microphysical prognostic variables, while on line 114, it is said “the five microphysical variable sets”. Is it four or five or am I mistaken and there are different microphysical variable sets?
Page 5, Line 116: Not sure why Fig2b is referenced.
Page 5, line 117: suggest to add “to” : “….temperature is used to preserve static……”
Page 6, line 152: Are the hourly rates of rainfall from observations or the model?
Page 14, line 282: Remove “a” before “only”
Page 16: Line 342: What is the reason for that the temperature sensitivity is higher in more polluted regions? This might have been stated earlier, but it would be good to spell it out again.
Page 18. Lines 394 – 401. I think it is worth including the study by Eidhammer et al (2018) here in the discussion as well. They looked at changes in drying ratio in a changing climate. They noted that the shape of the mountains and the wind speeds also have impacts on how the drying ratio changes with temperature. The difference between the current study and Siler and Roe and Krishbaum and Smith can therefore also be additional attributed to differences in the orography and windspeeds. Typically, wider mountain ranges have a lower change in drying ratio due to temperature increases compared to narrower mountains
Page 19, line 416. Eidhammer et al (2018) used downscaled climate simulation for their study on DR. In that study, the horizontal velocity changed between the current and future climate scenarios, and they showed the impact the changed velocity field had on the DR.
Page 19, line 434. I suggest adding citation of Kirshbaum et al and Eidhammer et al here regarding the rescaling of orography.
Eidhammer, T., V. GrubišiÄ, R. Rasmussen and K. Ikeda (2018), Winter precipitation efficiency of mountain ranges in the Colorado Rockies under climate change, J. Geophys. Res. 123, 2573-2590, https://doi.org/10.1002/2017JD027995.
Citation: https://doi.org/10.5194/egusphere-2022-740-RC2 -
RC3: 'Comment on egusphere-2022-740', Anonymous Referee #3, 02 Oct 2022
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-740/egusphere-2022-740-RC3-supplement.pdf
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AC1: 'Replies', Corinna Hoose, 30 Nov 2022
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-740/egusphere-2022-740-AC1-supplement.pdf
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2022-740', Anonymous Referee #1, 26 Sep 2022
Review of the manuscript entitled: “Temperature and CCN sensitivity of orographic precipitation enhanced by a mixed-phase seeder-feeder mechanism”.
The manuscript discusses the microphysical response of orographic precipitation to perturbations of temperature and cloud condensation nuclei (CCN) concentration. The authors provide technically sound analysis. There are, however, some comments that need to be addressed.
The manuscript contains English writing problems and needs to be carefully edited.
The first sentence of the Abstract is irrelevant to the subject of the manuscript and is better to be replaced by another sentence.
In the abstract and elsewhere, please replace “orographic rainfall” with “orographic precipitation”
It is better to remove the following sentence in the abstract or move it to the Introduction Section to have enough space to discuss the obtained results: “The study is motivated by the increased water vapour capacity of the atmosphere in a warming climate and the increasing frequency of extreme rainfall events."
Line 5: write out the full words for “ICON”
The Introduction is much weaker than the other parts of the manuscript and could be substantially improved. For example, the first paragraph of the Introduction does not provide any important information about the topic of the manuscript. It is irrelevant and can be omitted. Another example is in Line 22 where appropriate references and more clarification are required for the dynamic, thermodynamic, and microphysical contributions to precipitation changes under global warming. The microphysical contribution to precipitation changes is well discussed, but at least a few sentences can be added to explain the thermodynamic and dynamic contributions, particularly because the thermodynamic contribution to precipitation change is the main subject of the manuscript. As discussed in http://dx.doi.org/10.1007/s10584-022-03316-z, the precipitation response to climate change is regulated by two basic mechanisms, which include the wet-get-wetter mechanism and the warmer-get-wetter, both of which are referred to as the thermodynamic mechanism, while circulation changes under the impact of global warming which lead to precipitation changes are referred to as the dynamic change of precipitation.
Line 29: replace “by constant” with “be constant”
Line 34: Replace “English West coast” with “British West coast”
Line 45-46. Total precipitation might reduce or slightly change under a higher CCN concentration, but please note that some evidence suggests that heavy precipitation might increase in a polluted environment. For example, see the following paper: http://dx.doi.org/10.1016/j.atmosres.2016.10.021. This needs to be discussed in the Introduction, particularly because the importance of extreme precipitation and the risk of flooding is emphasized in the first paragraph of the introduction.
Line 49-50: This sentence does not mean anything: Which effect dominates highly depends on the synoptic conditions (e.g. whether convection is involved) and on the mountain geometry.
Line 56: westward or eastward?
Line 93: write out the full words in the first use of “DWD”
Parameterization schemes that are used for the boundary layer, radiation, etc. should be mentioned in Section 2.1
Lines 152-155: Rephrase the sentence.
Fig.4: It is better to start the label bar with white color representing zero value. Instead of using kg m-2 for the unit of precipitation, please consider writing it as mm for this figure and the others, although the values do not change.
Line 198-201. It is expected that heavy precipitation experiences the highest increase in response to warming, while light precipitation experiences a slight change or even decrease. It is interesting to compare the obtained results with those of http://dx.doi.org/ 10.1002/met.1724. This paper is already cited in the Introduction, but here or in the discussion section you can compare your results with their results and discuss the reasons for such behavior. In this paper, it is noted that more hygroscopic aerosols in the atmosphere could potentially increase heavy precipitation but reduce light precipitation. The author argued that an ample influx of water vapour over the regions with heavy precipitation could contribute to an increase of heavy precipitation under a polluted atmosphere, while less efficient autoconversion processes and/or increased cloud-top evaporation may contribute to a decrease in light precipitation. Could the same reasons contribute to an increase in heavy precipitation and a decrease in light precipitation in response to warming in your study? Please clarify. Such discussions could improve the quality of the manuscript.
Line 282: remove “a” before “only”
Line 407: Replace “in climate change” with “under climate change”
Citation: https://doi.org/10.5194/egusphere-2022-740-RC1 -
RC2: 'Comment on egusphere-2022-740', Anonymous Referee #2, 29 Sep 2022
This manuscript describes be sensitivity of precipitation efficiency with increased temperature and CCN concentration. I find the manuscript mostly well written and organized. The conclusions are justified and I think this manuscript should be published after some minor revisions.
Page 1, line 21: Can you provide a citation for the statement: “If there were no changes in cloud dynamics and microphysics, the total precipitation would increase by the same rate as total vapour inflow”
Page 2, line 35: When I first read through the manuscript, I questioned why specifically the English West Coast was mentioned. Later, when learning that the location of the Cambria flood is at the English Coast, I realized the importance. However, the Cambria flood has so far only been mentioned in the Abstract (and not given a more general location (the English West Coast)). I think a description of the Cambria flood needs to come before the statement of “enhanced precipitation along the English West coast”, or this statement needs to be moved.
Page 3, line 56: I suggest rewording to: “At the English West Coast, moist air flows that is moving westward over the Atlantic are ….”
Page 3, line 64: I suggest rephrasing to: “Only then are low mountain ranges (up to 1 km height) sufficient to ……”
Page 3, line 71: How long did the flood last? From 5th December to?
Page 3, line 71 to 77: This is a nice description of the Cumbria Flood and its area. I finally understand why the English West Coast is mentioned earlier. As mentioned in comment above, some description of the Cumbria Flood (at least location) needs to come before describing precipitation on the English West Coast so the reader understands why there is a focus on the English West coast.
Page 5, line 96: The triangular cells. This is the first time triangular cells are mentioned. Perhaps add a sentence how the grids are used in ICON.
Page 5, lines 112-114: On line 112 it is mentioned four sets of all microphysical prognostic variables, while on line 114, it is said “the five microphysical variable sets”. Is it four or five or am I mistaken and there are different microphysical variable sets?
Page 5, Line 116: Not sure why Fig2b is referenced.
Page 5, line 117: suggest to add “to” : “….temperature is used to preserve static……”
Page 6, line 152: Are the hourly rates of rainfall from observations or the model?
Page 14, line 282: Remove “a” before “only”
Page 16: Line 342: What is the reason for that the temperature sensitivity is higher in more polluted regions? This might have been stated earlier, but it would be good to spell it out again.
Page 18. Lines 394 – 401. I think it is worth including the study by Eidhammer et al (2018) here in the discussion as well. They looked at changes in drying ratio in a changing climate. They noted that the shape of the mountains and the wind speeds also have impacts on how the drying ratio changes with temperature. The difference between the current study and Siler and Roe and Krishbaum and Smith can therefore also be additional attributed to differences in the orography and windspeeds. Typically, wider mountain ranges have a lower change in drying ratio due to temperature increases compared to narrower mountains
Page 19, line 416. Eidhammer et al (2018) used downscaled climate simulation for their study on DR. In that study, the horizontal velocity changed between the current and future climate scenarios, and they showed the impact the changed velocity field had on the DR.
Page 19, line 434. I suggest adding citation of Kirshbaum et al and Eidhammer et al here regarding the rescaling of orography.
Eidhammer, T., V. GrubišiÄ, R. Rasmussen and K. Ikeda (2018), Winter precipitation efficiency of mountain ranges in the Colorado Rockies under climate change, J. Geophys. Res. 123, 2573-2590, https://doi.org/10.1002/2017JD027995.
Citation: https://doi.org/10.5194/egusphere-2022-740-RC2 -
RC3: 'Comment on egusphere-2022-740', Anonymous Referee #3, 02 Oct 2022
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-740/egusphere-2022-740-RC3-supplement.pdf
-
AC1: 'Replies', Corinna Hoose, 30 Nov 2022
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-740/egusphere-2022-740-AC1-supplement.pdf
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Journal article(s) based on this preprint
Julia Thomas et al.
Julia Thomas et al.
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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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