the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 11 Jun 2021
The contribution of transpiration, ground evaporation, and canopy evaporation to local and remote precipitation across North America
Abstract. Land surface evapotranspiration (ET) is a major source of moisture for the global hydrologic cycle. Though the influence of the land surface is well documented, moisture tracking analysis has often relied on offline tracking approaches that require simplifying assumptions and can bias results. Additionally, the contribution of the ET components (transpiration (T), canopy evaporation (C), and ground evaporation (E)) individually to precipitation is not well understood, inhibiting our understanding of moisture teleconnections in both the current and future climate. Here we use the Community Earth System Model version 1.2 with online numerical water tracers to examine the contribution of local and remote land surface ET, including the contribution from each individual ET component, to precipitation across North America. We find the role of the land surface and the individual ET components varies considerably across the continent and across seasons. Much of northern and northeastern North America receives up to 80% of summertime precipitation from land surface ET, and over 50 % of that moisture originates from transpiration alone. Local moisture recycling constitutes an essential source of precipitation across much of the southern and western regions of North America, while remote land surface moisture supplies most of the land-based precipitation across northern and eastern North America. Though the greatest contribution of remotely sourced land ET occurs in the north and east, we find the primary sources of North American land surface moisture shifts seasonally. The results highlight regions that are especially sensitive to land cover and hydrologic changes in local and upwind areas, providing key insights for drought prediction and water resource management.
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Status: closed
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RC1: 'Comment on hess-2021-284', Anonymous Referee #1, 02 Jul 2021
Review of "The contribution of transpiration, ground evaporation, and canopy evaporation to local and remote precipitation across North America" submitted to Hydrology and Earth System Sciences by Harrington et al. (https://doi.org/10.5194/hess-2021-284).
Summary:
This manuscript investigated the contribution of transpiration, ground evaporation, and canopy evaporation to local and remote precipitation across North America. They found that the role of the land surface and the individual ET components varies considerably across the continent and across seasons. In annual time scale, transpiration is the dominant source of precipitation across the north and east, while soil evaporation moisture is dominant in the south and west.
Comments:
I would recommend a major revision:
- Content needs to be condensed (see below). Many words should be removed since it is less important for the objective. It is really time-consuming to read those words.
- This is also related to comment 1. There appears to be little focus within this manuscript. In my opinion, the result section should be re-organized, and most of the words in the discussion should be moved to the result section. Meanwhile, I think the uncertainties of simulation should be discussed in detail in the discussion section.
- The method part is also unclear. Even though the authors provided an appendix to introduce the water tracers used in their study (it is hard to understand as well). It is still unclear why the author uses the isotope-enabled model to perform their simulation. Is isotope information used in this study? I did not find any information for it (I think it is not). Compared to other isotope-based studies (such as Yoshimura et al 2004; Sodemann et al., 2008 ), what is its advantage? Please specify.
Ref:
Yoshimura, Kei, et al. "Colored moisture analysis estimates of variations in 1998 Asian monsoon water sources." Journal of the Meteorological Society of Japan. Ser. II 82.5 (2004): 1315-1329.
Sodemann, H., Schwierz, C., & Wernli, H. (2008). Interannual variability of Greenland winter precipitation sources: Lagrangian moisture diagnostic and North Atlantic Oscillation influence. Journal of Geophysical Research, 113(D3). doi:10.1029/2007jd008503
4. The validation of simulation is not enough. The comparison of climatology mean of simulation and observation is not fair enough to check the model performance. We need more detailed metrics, such as RMSE, PBIAS etc. At the same time, since the author compares simulated ET with GLEAM, why not compare simulated transpiration, soil evaporation, and canopy interception with those from GLEAM as well?
Detailed comments
- L97-L104: I suggest removing these words. Since the model used in this study can not answer the question about how Lai and co2 will change the ET partitioning (I think the model used climatology mean LAI and constant values of Co2 in MS).
- L135-L138: Was isotope used here?
- L233: which version of the GLEAM dataset was used? Why not conduct a comparison of simulation and observed E, T, and C as well?
- L257: We need to see other metrics such as RMSE and PBIAS. Indeed, even for climatology mean, the bias is still considerable in my opinion (about 0.25 mm/day)
- L291: Again, other metrics such as RMSE or /and PBIAS are required.
- Section 3.3. Content needs to be condensed. Eq 6 should be moved to the method part.
- Section 3.5 and 3.6. Content needs to be condensed. I think to summarize as a table or Figure would be much better.
- L728-L751: move to the method section.
Citation: https://doi.org/10.5194/hess-2021-284-RC1 -
AC1: 'Reply on RC1', Tyler Harrington, 16 Aug 2021
Dear Anonymous Referee #1,
Summary:
Thank you for your constructive feedback to help improve our manuscript. We will address each of your specific suggestions below and indicate how we plan to revise our manuscript.
This manuscript investigated the contribution of transpiration, ground evaporation, and canopy evaporation to local and remote precipitation across North America. They found that the role of the land surface and the individual ET components varies considerably across the continent and across seasons. In annual time scale, transpiration is the dominant source of precipitation across the north and east, while soil evaporation moisture is dominant in the south and west.
Comments:
I would recommend a major revision:
- Content needs to be condensed (see below). Many words should be removed since it is less important for the objective. It is really time-consuming to read those words.
We will condense the discussion section to help cut back on the length of the manuscript. Specifically, we will remove portions of the discussion section that repeat information from the results section. This will help reduce the total word count.
- This is also related to comment 1. There appears to be little focus within this manuscript. In my opinion, the result section should be re-organized, and most of the words in the discussion should be moved to the result section. Meanwhile, I think the uncertainties of simulation should be discussed in detail in the discussion section.
The results section is organized in the following way: a comparison of model output to observations, an examination of total ET to precipitation, recycling, and moisture export, and an examination of each individual ET component to precipitation, recycling, and moisture export. Most of the research literature examines land surface ET in each of these processes, but does not investigate each component individually. We believe organizing our results section in this way first provides the reader with information that can be directly compared to other studies (though we look at recycling and export on a more refined spatial scale than many other studies), and then provides a further analysis by repeating the results for the individual ET components. As such, we prefer to keep the results section organized in this way.
As addressed in the previous comment, we plan to reduce the length of the discussion section. We will remove the parts of the discussion section that could be directly moved into the results section. We will also address uncertainties of our results given the constraints of the model, including those related to biases and model parameterizations.
- The method part is also unclear. Even though the authors provided an appendix to introduce the water tracers used in their study (it is hard to understand as well). It is still unclear why the author uses the isotope-enabled model to perform their simulation. Is isotope information used in this study? I did not find any information for it (I think it is not). Compared to other isotope-based studies (such as Yoshimura et al 2004; Sodemann et al., 2008 ), what is its advantage? Please specify.
Ref:
Yoshimura, Kei, et al. "Colored moisture analysis estimates of variations in 1998 Asian monsoon water sources." Journal of the Meteorological Society of Japan. Ser. II 82.5 (2004): 1315-1329.
Sodemann, H., Schwierz, C., & Wernli, H. (2008). Interannual variability of Greenland winter precipitation sources: Lagrangian moisture diagnostic and North Atlantic Oscillation influence. Journal of Geophysical Research, 113(D3). doi:10.1029/2007jd008503
The version of the Community Earth System Model that has water tracing capabilities is the isotope-enabled Community Earth System Model (iCESM). Though iCESM is needed to use the water tracers, isotopes are not used in the tracking nor in any of our analysis. We will add a couple of sentences to our methods section to clarify that isotopes are not used in our study.
- The validation of simulation is not enough. The comparison of climatology mean of simulation and observation is not fair enough to check the model performance. We need more detailed metrics, such as RMSE, PBIAS etc. At the same time, since the author compares simulated ET with GLEAM, why not compare simulated transpiration, soil evaporation, and canopy interception with those from GLEAM as well?
Thank you for this suggestion. We agree that more validation metrics can be useful to check our model performance. Though RMSE is a great metric for validating model performance, (Willmott & Matsuura, 2005) showed MAE is more appropriate for assessing climate model performance. We will include a Supplemental Table in our revised manuscript that shows the MAE and PBIAS for each region of our study domain for precipitation, ET, and each ET component.
In regards to comparing our model simulation to GLEAM transpiration, soil evaporation, and canopy interception separately, these comparisons are included in the supplemental document (Figures S1-S3) of our current manuscript.
Ref:
Willmott, C.J. and Matsuura, K. (2005) Advantages of the Mean Absolute Error (MAE) over the Root Mean Square Error (RMSE) in Assessing Average Model Performance. Climate Research, 30, 79-82. http://dx.doi.org/10.3354/cr030079
Detailed comments
- L97-L104: I suggest removing these words. Since the model used in this study can not answer the question about how Lai and co2 will change the ET partitioning (I think the model used climatology mean LAI and constant values of Co2 in MS).
While the model does not answer the question about how LAI and CO2 will change future ET partitioning, the partitioning of ET impacts moisture teleconnections (as we show in this manuscript). Understanding how future moisture teleconnections may change starts with understanding moisture teleconnections in the current climate. We believe including this section in our introduction serves as great motivation for our study, and would prefer to keep this text.
- L135-L138: Was isotope used here?
No isotopes are used in our study. We will make sure to note this in the methods section.
- L233: which version of the GLEAM dataset was used? Why not conduct a comparison of simulation and observed E, T, and C as well?
We used GLEAM version 3.5a and will note this in the Methods section of our revised manuscript. We have compared the simulated E, T, and C to GLEAM. These comparisons are shown in the supplemental document (Figures S1-S3) and referenced in Section 3.2.
- L257: We need to see other metrics such as RMSE and PBIAS. Indeed, even for climatology mean, the bias is still considerable in my opinion (about 0.25 mm/day)
We will add a supplemental table that lists the MAE and PBIAS for each region.
- L291: Again, other metrics such as RMSE or /and PBIAS are required.
We will add a supplemental table that lists the MAE and PBIAS for each region.
- Section 3.3. Content needs to be condensed. Eq 6 should be moved to the method part.
While we do not believe we can remove the majority of the text from this section without removing valuable results, we will be more concise with our words and will remove any extraneous information to reduce the Section’s length. We also agree that most equations should be included in the methods section. However, the need for this equation arises in Section 3.4, and we believe incorporating this equation within our results (along with references to other manuscripts showing the need for this equation) is easier for the reader to follow.
- Section 3.5 and 3.6. Content needs to be condensed. I think to summarize as a table or Figure would be much better.
Sections 3.5 and 3.6 describe the seasonal evolution of regional moisture convergence/divergence, and the breakdown of the individual ET component contributions to precipitation, respectively. The results presented in these sections are key for understanding the teleconnections between regions, and for understanding the relative importance of transpiration, canopy evaporation, and ground evaporation in driving local and remote precipitation.
While we do not believe we can remove the majority of the text in these sections without removing valuable results, we will be more concise with our words and will remove any extraneous information to reduce each Section’s length. Figure 7 combines all of Section 3.5 into one Figure to hopefully make seasonal comparisons easy for the reader.
- L728-L751: move to the method section.
We will move this to the methods section.
Citation: https://doi.org/10.5194/hess-2021-284-AC1
-
RC2: 'Comment on hess-2021-284', Anonymous Referee #2, 02 Jul 2021
General comments:
This paper analyzed regional moisture recycling and precipitation sources to individual ET components (transpiration (T), canopy evaporation (C), and ground evaporation (E)) by using the Community Earth System Model version 1.2 with online numerical water tracers, and found the role of the land surface and each individual ET components across North America and across seasons. It is found that the northern part of study area receives more contribution from land surface (80%), more than half of which originates from T moisture, while E moisture is dominant in the south and west. Meanwhile, the contributions of each component to recycling varies by season. During winter and fall E and C moisture make up a large proportion, while the summer is dominated by T, and the spring receives high contributions from all three components. This study separates the contribution from each ET components, which is of scientific significance. This paper is well-organized and well-written, and it can be accepted after the following questions are revised or explained.
Specific comments
1. Although the title is “The contribution of transpiration, ground evaporation, and canopy evaporation to local and remote precipitation across North America”, the study focuses only on precipitation in North America, while the sources are distinguished between local and remote. A revision of the title is suggested to emphasize local and remote contribution of the ET components to North America precipitation.
2. Line 49: “including the contributions from moisture transport and recycling”. It will be better to replace “moisture transport” with “moisture advection”.
3. Line 192: I do not get the meaning of this calculation equation and what it is trying to express here.
4. Line 395-396: “This scaling ensures that regions with…is not solely a function of domain size”: Please note that the local recycling ratio, or percent recycling in this paper, is not solely a function of area, but is also closely related to the local land-atmosphere coupling and circulation conditions. It is more appropriate to say that normalization can eliminate the impact of the size of the land area to a certain extent.
5. Figure7: Line 568 “All units are normalized units of length per m-1”. Please check if is should be “per m”. And what are the units of each variable itself? For example, is the unit of evaporation in mm day-1 and then normalized to per m? And what about divergence/convergence?
6. All the figures in the result section do not show the latitude and longitude range, I suggest adding it. And keep all figures showing the same range.
7. For Figure9-12, if the contribution of the same component in different seasons can be represented by the same range of colorbars, it will be easier for the reader to compare changes between seasons.
Citation: https://doi.org/10.5194/hess-2021-284-RC2 -
AC2: 'Reply on RC2', Tyler Harrington, 16 Aug 2021
Dear Anonymous Referee #2,
Thank you for your constructive feedback to help improve our manuscript. We will address each of your specific suggestions below and indicate how we plan to revise our manuscript.
General comments:
This paper analyzed regional moisture recycling and precipitation sources to individual ET components (transpiration (T), canopy evaporation (C), and ground evaporation (E)) by using the Community Earth System Model version 1.2 with online numerical water tracers, and found the role of the land surface and each individual ET components across North America and across seasons. It is found that the northern part of study area receives more contribution from land surface (80%), more than half of which originates from T moisture, while E moisture is dominant in the south and west. Meanwhile, the contributions of each component to recycling varies by season. During winter and fall E and C moisture make up a large proportion, while the summer is dominated by T, and the spring receives high contributions from all three components. This study separates the contribution from each ET components, which is of scientific significance. This paper is well-organized and well-written, and it can be accepted after the following questions are revised or explained.
Specific comments
- Although the title is “The contribution of transpiration, ground evaporation, and canopy evaporation to local and remote precipitation across North America”, the study focuses only on precipitation in North America, while the sources are distinguished between local and remote. A revision of the title is suggested to emphasize local and remote contribution of the ET components to North America precipitation.
Thank you for this suggestion. We agree the local and remote contribution of the ET components should be emphasized, so we will change our title to “The contribution of local and remote transpiration, ground evaporation, and canopy evaporation to precipitation across North America”.
- Line 49: “including the contributions from moisture transport and recycling”. It will be better to replace “moisture transport” with “moisture advection”.
We will make this change.
- Line 192: I do not get the meaning of this calculation equation and what it is trying to express here.
We include this equation to show that the matrix formulation developed in Singh et al. 2016 only works if all precipitation and evaporation over all the Earth’s surface area is considered. Since we only consider evaporation & precipitation that occurs over the North American continent, we have to adjust their matrix formulation (as shown in the appendix). We will include some extra clarification about this in the methods section of our revised manuscript.
- Line 395-396: “This scaling ensures that regions with…is not solely a function of domain size”: Please note that the local recycling ratio, or percent recycling in this paper, is not solely a function of area, but is also closely related to the local land-atmosphere coupling and circulation conditions. It is more appropriate to say that normalization can eliminate the impact of the size of the land area to a certain extent.
Thank you for this suggestion. We will change “this scaling ensures that regions with… is not solely a function of domain size” to “the scaling term helps to minimize the impact of domain size on recycling percentages”.
- Figure7: Line 568 “All units are normalized units of length per m-1”. Please check if is should be “per m”. And what are the units of each variable itself? For example, is the unit of evaporation in mm day-1and then normalized to per m? And what about divergence/convergence?
Thank you for catching this mistake. We will change line 568 to per m rather than per m^-1. We also agree that our length per m units are difficult to interpret. We will clarify that length per m for the evaporation plots refers to the “normalized water amount per m” and the convergence/divergence plots refers to the “normalized water mass flux per m”.
- All the figures in the result section do not show the latitude and longitude range, I suggest adding it. And keep all figures showing the same range.
We will make this change to all of our map plots.
- For Figure9-12, if the contribution of the same component in different seasons can be represented by the same range of colorbars, it will be easier for the reader to compare changes between seasons.
We will make sure that each ET component has the same colorbar scale for all seasons.
Citation: https://doi.org/10.5194/hess-2021-284-AC2
-
AC2: 'Reply on RC2', Tyler Harrington, 16 Aug 2021
Status: closed
-
RC1: 'Comment on hess-2021-284', Anonymous Referee #1, 02 Jul 2021
Review of "The contribution of transpiration, ground evaporation, and canopy evaporation to local and remote precipitation across North America" submitted to Hydrology and Earth System Sciences by Harrington et al. (https://doi.org/10.5194/hess-2021-284).
Summary:
This manuscript investigated the contribution of transpiration, ground evaporation, and canopy evaporation to local and remote precipitation across North America. They found that the role of the land surface and the individual ET components varies considerably across the continent and across seasons. In annual time scale, transpiration is the dominant source of precipitation across the north and east, while soil evaporation moisture is dominant in the south and west.
Comments:
I would recommend a major revision:
- Content needs to be condensed (see below). Many words should be removed since it is less important for the objective. It is really time-consuming to read those words.
- This is also related to comment 1. There appears to be little focus within this manuscript. In my opinion, the result section should be re-organized, and most of the words in the discussion should be moved to the result section. Meanwhile, I think the uncertainties of simulation should be discussed in detail in the discussion section.
- The method part is also unclear. Even though the authors provided an appendix to introduce the water tracers used in their study (it is hard to understand as well). It is still unclear why the author uses the isotope-enabled model to perform their simulation. Is isotope information used in this study? I did not find any information for it (I think it is not). Compared to other isotope-based studies (such as Yoshimura et al 2004; Sodemann et al., 2008 ), what is its advantage? Please specify.
Ref:
Yoshimura, Kei, et al. "Colored moisture analysis estimates of variations in 1998 Asian monsoon water sources." Journal of the Meteorological Society of Japan. Ser. II 82.5 (2004): 1315-1329.
Sodemann, H., Schwierz, C., & Wernli, H. (2008). Interannual variability of Greenland winter precipitation sources: Lagrangian moisture diagnostic and North Atlantic Oscillation influence. Journal of Geophysical Research, 113(D3). doi:10.1029/2007jd008503
4. The validation of simulation is not enough. The comparison of climatology mean of simulation and observation is not fair enough to check the model performance. We need more detailed metrics, such as RMSE, PBIAS etc. At the same time, since the author compares simulated ET with GLEAM, why not compare simulated transpiration, soil evaporation, and canopy interception with those from GLEAM as well?
Detailed comments
- L97-L104: I suggest removing these words. Since the model used in this study can not answer the question about how Lai and co2 will change the ET partitioning (I think the model used climatology mean LAI and constant values of Co2 in MS).
- L135-L138: Was isotope used here?
- L233: which version of the GLEAM dataset was used? Why not conduct a comparison of simulation and observed E, T, and C as well?
- L257: We need to see other metrics such as RMSE and PBIAS. Indeed, even for climatology mean, the bias is still considerable in my opinion (about 0.25 mm/day)
- L291: Again, other metrics such as RMSE or /and PBIAS are required.
- Section 3.3. Content needs to be condensed. Eq 6 should be moved to the method part.
- Section 3.5 and 3.6. Content needs to be condensed. I think to summarize as a table or Figure would be much better.
- L728-L751: move to the method section.
Citation: https://doi.org/10.5194/hess-2021-284-RC1 -
AC1: 'Reply on RC1', Tyler Harrington, 16 Aug 2021
Dear Anonymous Referee #1,
Summary:
Thank you for your constructive feedback to help improve our manuscript. We will address each of your specific suggestions below and indicate how we plan to revise our manuscript.
This manuscript investigated the contribution of transpiration, ground evaporation, and canopy evaporation to local and remote precipitation across North America. They found that the role of the land surface and the individual ET components varies considerably across the continent and across seasons. In annual time scale, transpiration is the dominant source of precipitation across the north and east, while soil evaporation moisture is dominant in the south and west.
Comments:
I would recommend a major revision:
- Content needs to be condensed (see below). Many words should be removed since it is less important for the objective. It is really time-consuming to read those words.
We will condense the discussion section to help cut back on the length of the manuscript. Specifically, we will remove portions of the discussion section that repeat information from the results section. This will help reduce the total word count.
- This is also related to comment 1. There appears to be little focus within this manuscript. In my opinion, the result section should be re-organized, and most of the words in the discussion should be moved to the result section. Meanwhile, I think the uncertainties of simulation should be discussed in detail in the discussion section.
The results section is organized in the following way: a comparison of model output to observations, an examination of total ET to precipitation, recycling, and moisture export, and an examination of each individual ET component to precipitation, recycling, and moisture export. Most of the research literature examines land surface ET in each of these processes, but does not investigate each component individually. We believe organizing our results section in this way first provides the reader with information that can be directly compared to other studies (though we look at recycling and export on a more refined spatial scale than many other studies), and then provides a further analysis by repeating the results for the individual ET components. As such, we prefer to keep the results section organized in this way.
As addressed in the previous comment, we plan to reduce the length of the discussion section. We will remove the parts of the discussion section that could be directly moved into the results section. We will also address uncertainties of our results given the constraints of the model, including those related to biases and model parameterizations.
- The method part is also unclear. Even though the authors provided an appendix to introduce the water tracers used in their study (it is hard to understand as well). It is still unclear why the author uses the isotope-enabled model to perform their simulation. Is isotope information used in this study? I did not find any information for it (I think it is not). Compared to other isotope-based studies (such as Yoshimura et al 2004; Sodemann et al., 2008 ), what is its advantage? Please specify.
Ref:
Yoshimura, Kei, et al. "Colored moisture analysis estimates of variations in 1998 Asian monsoon water sources." Journal of the Meteorological Society of Japan. Ser. II 82.5 (2004): 1315-1329.
Sodemann, H., Schwierz, C., & Wernli, H. (2008). Interannual variability of Greenland winter precipitation sources: Lagrangian moisture diagnostic and North Atlantic Oscillation influence. Journal of Geophysical Research, 113(D3). doi:10.1029/2007jd008503
The version of the Community Earth System Model that has water tracing capabilities is the isotope-enabled Community Earth System Model (iCESM). Though iCESM is needed to use the water tracers, isotopes are not used in the tracking nor in any of our analysis. We will add a couple of sentences to our methods section to clarify that isotopes are not used in our study.
- The validation of simulation is not enough. The comparison of climatology mean of simulation and observation is not fair enough to check the model performance. We need more detailed metrics, such as RMSE, PBIAS etc. At the same time, since the author compares simulated ET with GLEAM, why not compare simulated transpiration, soil evaporation, and canopy interception with those from GLEAM as well?
Thank you for this suggestion. We agree that more validation metrics can be useful to check our model performance. Though RMSE is a great metric for validating model performance, (Willmott & Matsuura, 2005) showed MAE is more appropriate for assessing climate model performance. We will include a Supplemental Table in our revised manuscript that shows the MAE and PBIAS for each region of our study domain for precipitation, ET, and each ET component.
In regards to comparing our model simulation to GLEAM transpiration, soil evaporation, and canopy interception separately, these comparisons are included in the supplemental document (Figures S1-S3) of our current manuscript.
Ref:
Willmott, C.J. and Matsuura, K. (2005) Advantages of the Mean Absolute Error (MAE) over the Root Mean Square Error (RMSE) in Assessing Average Model Performance. Climate Research, 30, 79-82. http://dx.doi.org/10.3354/cr030079
Detailed comments
- L97-L104: I suggest removing these words. Since the model used in this study can not answer the question about how Lai and co2 will change the ET partitioning (I think the model used climatology mean LAI and constant values of Co2 in MS).
While the model does not answer the question about how LAI and CO2 will change future ET partitioning, the partitioning of ET impacts moisture teleconnections (as we show in this manuscript). Understanding how future moisture teleconnections may change starts with understanding moisture teleconnections in the current climate. We believe including this section in our introduction serves as great motivation for our study, and would prefer to keep this text.
- L135-L138: Was isotope used here?
No isotopes are used in our study. We will make sure to note this in the methods section.
- L233: which version of the GLEAM dataset was used? Why not conduct a comparison of simulation and observed E, T, and C as well?
We used GLEAM version 3.5a and will note this in the Methods section of our revised manuscript. We have compared the simulated E, T, and C to GLEAM. These comparisons are shown in the supplemental document (Figures S1-S3) and referenced in Section 3.2.
- L257: We need to see other metrics such as RMSE and PBIAS. Indeed, even for climatology mean, the bias is still considerable in my opinion (about 0.25 mm/day)
We will add a supplemental table that lists the MAE and PBIAS for each region.
- L291: Again, other metrics such as RMSE or /and PBIAS are required.
We will add a supplemental table that lists the MAE and PBIAS for each region.
- Section 3.3. Content needs to be condensed. Eq 6 should be moved to the method part.
While we do not believe we can remove the majority of the text from this section without removing valuable results, we will be more concise with our words and will remove any extraneous information to reduce the Section’s length. We also agree that most equations should be included in the methods section. However, the need for this equation arises in Section 3.4, and we believe incorporating this equation within our results (along with references to other manuscripts showing the need for this equation) is easier for the reader to follow.
- Section 3.5 and 3.6. Content needs to be condensed. I think to summarize as a table or Figure would be much better.
Sections 3.5 and 3.6 describe the seasonal evolution of regional moisture convergence/divergence, and the breakdown of the individual ET component contributions to precipitation, respectively. The results presented in these sections are key for understanding the teleconnections between regions, and for understanding the relative importance of transpiration, canopy evaporation, and ground evaporation in driving local and remote precipitation.
While we do not believe we can remove the majority of the text in these sections without removing valuable results, we will be more concise with our words and will remove any extraneous information to reduce each Section’s length. Figure 7 combines all of Section 3.5 into one Figure to hopefully make seasonal comparisons easy for the reader.
- L728-L751: move to the method section.
We will move this to the methods section.
Citation: https://doi.org/10.5194/hess-2021-284-AC1
-
RC2: 'Comment on hess-2021-284', Anonymous Referee #2, 02 Jul 2021
General comments:
This paper analyzed regional moisture recycling and precipitation sources to individual ET components (transpiration (T), canopy evaporation (C), and ground evaporation (E)) by using the Community Earth System Model version 1.2 with online numerical water tracers, and found the role of the land surface and each individual ET components across North America and across seasons. It is found that the northern part of study area receives more contribution from land surface (80%), more than half of which originates from T moisture, while E moisture is dominant in the south and west. Meanwhile, the contributions of each component to recycling varies by season. During winter and fall E and C moisture make up a large proportion, while the summer is dominated by T, and the spring receives high contributions from all three components. This study separates the contribution from each ET components, which is of scientific significance. This paper is well-organized and well-written, and it can be accepted after the following questions are revised or explained.
Specific comments
1. Although the title is “The contribution of transpiration, ground evaporation, and canopy evaporation to local and remote precipitation across North America”, the study focuses only on precipitation in North America, while the sources are distinguished between local and remote. A revision of the title is suggested to emphasize local and remote contribution of the ET components to North America precipitation.
2. Line 49: “including the contributions from moisture transport and recycling”. It will be better to replace “moisture transport” with “moisture advection”.
3. Line 192: I do not get the meaning of this calculation equation and what it is trying to express here.
4. Line 395-396: “This scaling ensures that regions with…is not solely a function of domain size”: Please note that the local recycling ratio, or percent recycling in this paper, is not solely a function of area, but is also closely related to the local land-atmosphere coupling and circulation conditions. It is more appropriate to say that normalization can eliminate the impact of the size of the land area to a certain extent.
5. Figure7: Line 568 “All units are normalized units of length per m-1”. Please check if is should be “per m”. And what are the units of each variable itself? For example, is the unit of evaporation in mm day-1 and then normalized to per m? And what about divergence/convergence?
6. All the figures in the result section do not show the latitude and longitude range, I suggest adding it. And keep all figures showing the same range.
7. For Figure9-12, if the contribution of the same component in different seasons can be represented by the same range of colorbars, it will be easier for the reader to compare changes between seasons.
Citation: https://doi.org/10.5194/hess-2021-284-RC2 -
AC2: 'Reply on RC2', Tyler Harrington, 16 Aug 2021
Dear Anonymous Referee #2,
Thank you for your constructive feedback to help improve our manuscript. We will address each of your specific suggestions below and indicate how we plan to revise our manuscript.
General comments:
This paper analyzed regional moisture recycling and precipitation sources to individual ET components (transpiration (T), canopy evaporation (C), and ground evaporation (E)) by using the Community Earth System Model version 1.2 with online numerical water tracers, and found the role of the land surface and each individual ET components across North America and across seasons. It is found that the northern part of study area receives more contribution from land surface (80%), more than half of which originates from T moisture, while E moisture is dominant in the south and west. Meanwhile, the contributions of each component to recycling varies by season. During winter and fall E and C moisture make up a large proportion, while the summer is dominated by T, and the spring receives high contributions from all three components. This study separates the contribution from each ET components, which is of scientific significance. This paper is well-organized and well-written, and it can be accepted after the following questions are revised or explained.
Specific comments
- Although the title is “The contribution of transpiration, ground evaporation, and canopy evaporation to local and remote precipitation across North America”, the study focuses only on precipitation in North America, while the sources are distinguished between local and remote. A revision of the title is suggested to emphasize local and remote contribution of the ET components to North America precipitation.
Thank you for this suggestion. We agree the local and remote contribution of the ET components should be emphasized, so we will change our title to “The contribution of local and remote transpiration, ground evaporation, and canopy evaporation to precipitation across North America”.
- Line 49: “including the contributions from moisture transport and recycling”. It will be better to replace “moisture transport” with “moisture advection”.
We will make this change.
- Line 192: I do not get the meaning of this calculation equation and what it is trying to express here.
We include this equation to show that the matrix formulation developed in Singh et al. 2016 only works if all precipitation and evaporation over all the Earth’s surface area is considered. Since we only consider evaporation & precipitation that occurs over the North American continent, we have to adjust their matrix formulation (as shown in the appendix). We will include some extra clarification about this in the methods section of our revised manuscript.
- Line 395-396: “This scaling ensures that regions with…is not solely a function of domain size”: Please note that the local recycling ratio, or percent recycling in this paper, is not solely a function of area, but is also closely related to the local land-atmosphere coupling and circulation conditions. It is more appropriate to say that normalization can eliminate the impact of the size of the land area to a certain extent.
Thank you for this suggestion. We will change “this scaling ensures that regions with… is not solely a function of domain size” to “the scaling term helps to minimize the impact of domain size on recycling percentages”.
- Figure7: Line 568 “All units are normalized units of length per m-1”. Please check if is should be “per m”. And what are the units of each variable itself? For example, is the unit of evaporation in mm day-1and then normalized to per m? And what about divergence/convergence?
Thank you for catching this mistake. We will change line 568 to per m rather than per m^-1. We also agree that our length per m units are difficult to interpret. We will clarify that length per m for the evaporation plots refers to the “normalized water amount per m” and the convergence/divergence plots refers to the “normalized water mass flux per m”.
- All the figures in the result section do not show the latitude and longitude range, I suggest adding it. And keep all figures showing the same range.
We will make this change to all of our map plots.
- For Figure9-12, if the contribution of the same component in different seasons can be represented by the same range of colorbars, it will be easier for the reader to compare changes between seasons.
We will make sure that each ET component has the same colorbar scale for all seasons.
Citation: https://doi.org/10.5194/hess-2021-284-AC2
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AC2: 'Reply on RC2', Tyler Harrington, 16 Aug 2021
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