the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 14 Feb 2023
Influence of the previous North Atlantic Oscillation (NAO) on the spring dust aerosols over North China
Abstract. The North Atlantic Oscillation (NAO) has been confirmed to be closely related to the weather-climate in many regions of the Northern Hemisphere, however, its effect and mechanism upon the formation of regional dust events (DEs) have rarely been involved in China. By using the station observation data, and multi reanalysis datasets, the influence of NAO on the dust aerosols (DAs) in China, as well as the corresponding mechanism of synoptic cause are explored in perspective of transient eddy fluxes. It is found that the DAs in the non-dust source areas show high values with a strong annual variability in north of the Yangtze River (30–40° N, 105–120° E), which is referred to as the North China hereafter. A significant negative relationship is indicated between the boreal winter NAO index and the late spring DAs in the North China with the correlation coefficient of −0.39. According to the 9 spring DEs affected significantly by negative phase of the preceding winter NAO in the North China during 1980–2020, it is shown that before the outbreak of DEs, due to the transient eddy momentum (heat) convergence (divergence) over the dust aerosol (DA) source regions, the zonal wind speed increases in upper-level troposphere, strengthening the zonal wind in the middle-lower levels through momentum downward transmission. Simultaneously, there is transient eddy momentum (heat) divergence (convergence) around the Ural Mountains, which is favorable for establishment and maintenance of the Ural ridge, as well as development of the air temperature and vorticity advections. The combined action of temperature and vorticity advections results in the Siberian Highs and Mongolian cyclone to establish, strengthen, and move southward near the surface, guiding the cold air from high latitudes southward, and is favorable to the uplift and transmission of DAs to the downstream North China. After the outbreak of DEs, change of transient eddy fluxes in the DA source regions and the Urals regions, leads to both energy and mass divergence and reduction of the zonal winds over the North China. Accompanying with the prevailing southerly airflow in south of the North China, a stable high value of DA concentration is maintained for 1–2 days. This study reveals the impact of transient eddy fluxes transport on the dusty weather anomalies modulated by the NAO negative signal in the North China, which can deepen the understanding of formation mechanism of DEs in China.
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Notice on discussion status
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
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2023-52', Anonymous Referee #1, 08 Mar 2023
Using the station observations and multi reanalysis data, the authors investigated the possible influences of the previous NAO on the dust aerosols over northern China. Authors concluded that the boreal winter NAO has significant impacts on the following spring dust aerosols, particularly during the negative phase of the NAO. The thermal and dynamical processes relevant to the anomalous NAO on the circulation are analyzed, and it indicated that the impact of transient eddy fluxes transport plays important role in the formation of the dust aerosol events. I agree with the authors that the influence of previous NAO on dust aerosols in China cannot be ignored. And it is an important interdisciplinary issue that needs more attention and deep research. Overall the manuscript is well written and clear, and the figures are also appropriate and clear. However, there are some problems with this manuscript, and it cannot be accepted by ACP as it is now. Some specific comments or suggestions are listed as follows:
(1) Introduction: the review of the dust aerosol’s climate effect and the NAO’s impacts on the regional climate anomalies are a little repetitive and lengthy. Address and summary the major research progress of the present work.
(2) NAO index: There are lots of definitions of the NAOI, what is the advantage of the NAOI used, and whether the result is robust if other definitions are used. The authors need to further compare the different NAOI, and clarify whether the result is subject to the NAOI.
(3) The role of previous winter NAO on the following spring dust aerosols is discussed, however, as reported ENSO shows a significant role in determining the winter and spring climate anomalies over eastern China. it is of interest to further discuss whether the impacts of NAO on the aerosols are independent of ENSO.
(4) L218: prior to rather than previous to
(5) Line 34: The descriptions are confusing.
(6) In the upper troposphere, it is emphasized that both the jet stream and downward transmission of high-altitude wind speed momentum contribute to the formation of the dust aerosols, however, without a detailed physical explanation of the combined role the two.
(7) In the middle troposphere, the evolution of the trough-ridge system along with the occurrence of the dust aerosol events should be further analyzed. The involved physical process, particularly, which variable is more important in the process warranty further illustration.
(8) There are lots of clerical errors, i.e.,
L306, should be 0.1 in and 0.2 in
L351, should be 35°-50°N, 70°-110°E
L356-360, lengthy and repetition
L377, should be prior to
L404, should be 30°-60°N, 105°-130°E
The authors should carefully check the whole manuscript.
(9) Figures 2, 4, 7, 10, 13, without clarification of the axis, Figure 3, without units.Citation: https://doi.org/10.5194/egusphere-2023-52-RC1 - AC1: 'Reply on RC1', Fa lei Xu, 17 Apr 2023
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RC2: 'Comment on egusphere-2023-52', Anonymous Referee #2, 11 Mar 2023
General comments:
This study investigated the relationship between the boreal winter North Atlantic Oscillation (NAO) and the spring dust events (DEs) over North China (30-40°N, 105-120°E) during 1980-2020. The authors demonstrated that there is a significant negative relationship between the boreal winter NAO index and the late spring DAs in the North China. The synoptic cause of such relation is characterized as the changes in the tropospheric synoptic situation in the Ural Mountains, DAs source regions in China, and North China during the DEs under the modulation of the NAO negative signal. Further, evolution mechanism of abnormal atmospheric circulation affected by the NAO negative signal is explained by the transient eddy fluxes transport, thermal wind principle, and the quasi-geostrophic theory.
This paper is very meaningful, and a great quantity of previous work has been summarized and cited. The results of this study are interesting and useful to deepen our understanding of formation mechanism of the DEs in east Asia. I would like to recommend this manuscript should be accepted subject to minor revision, for this study fit well with the scope of Atmospheric Chemistry and Physics.
Specific comments are as follows.
- Line 85: “it is of important practical”. I suggest deleting “of” in the sentence.
- Line 155,450,471: “mechanisms”. I suggest revising it as “mechanism” and pay more attention to tenses of verbs.
- Line 140: “the DEs in northern China regions”. I suggest deleting “regions”.
- Line 192-195: The full name of the ERA5 reanalysis datasets is not correct.
- Line 208-210: What is the exact definition of selection criteria for the NAO abnormal years? Please describe it specifically.
- Line 259: “in DJF, JFM, and FMA in the early period”. I suggest revising it as “in previous DJF, JFM, and FMA”.
- Line 278: Figure 3, units needed.
- Line 310-311: Information of the 27 DEs seems not enough. It is suggested to list 27 DEs and the years in which these DEs occurred in a table, which may be easier for readers to understand better.
- Line 316-321: It is not clear how the 9 DEs are selected from the climate scale and the weather scale. It is better to be described in detail by means of figures or tables.
- Line 404: Should be (30°-60°N, 105-130°E).
- Line 579,603: The citation of references (Gary, 2011) should be revised as (Gary, 2012).
- Line 728-730: The author also mentioned that both NAO and ENSO play important role in the occurrence and development of DEs in China, and the research on such synergistic effects is relatively little yet. Have you got some preliminary results? Or the authors could conduct research on this issue in the next step of work.
- The labels in some figures (Figure 7, Figure 10-13) should be further enlarged, since they are rather small to distinguish.
Citation: https://doi.org/10.5194/egusphere-2023-52-RC2 - AC2: 'Reply on RC2', Fa lei Xu, 17 Apr 2023
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RC3: 'Comment on egusphere-2023-52', Anonymous Referee #3, 11 Mar 2023
This study investigates the impacts of North Atlantic Oscillation (NAO) on spring dust aerosols over North China based on station observation data and multi reanalysis datasets. They found that late spring dust aerosols are negatively correlated with the boreal winter NAO index. They further illustrate that the changes in transient eddy momentum over the dust source region the Ural Mountains could explain the relative high spring dust levels following the negative winter NAO events. The topic is interesting and method is sound. I recommend it can be published after addressing my minor comments below.
My main comment is about how is the station observation of dust events and reanalysis data connected. Many results of this study are based on MERRA-2 dust column mass. However, how the MERRA-2 captures the dust events over the 41-years, especially those related to the negative NAO, comparing to the surface observation should be examined. Also, the dust events are separated into dust storm, blowing dust and floating dust. Are they show the same relationship with NAO?
Minor comments:
In the abstract, the correlation coefficient between the boreal winter NAO index and the late spring DAs in the North China is -0.39, but I did not find thin value in the main text (probably in line 260).
Line 54: Studies also reported that the dust can interact with winds in China through its radiative effect, which further weakens winds during weak wind years in winter over North China (e.g., Yang et al., 2017).
The authors explain the impacts of NAO on dust in North China through changes in energy and large-scale circulation. But they also showed that NAO can cause unusual rainy climate, which can influence the wet removal of dust. How this effect considered in the study.
The mechanism of the NAO impacts may not be only limited to dust in China, but also dust over the central Asia and North Africa. The authors could add some discussion about it.
Reference:
Yang, Y., Russell, L. M., Lou, S., Liao, H., Guo, J., Liu, Y., Singh, B., and Ghan, S. J.: Dust-wind interactions can intensify aerosol pollution over eastern China, Nat. Commun., 8, 15333, https://doi.org/10.1038/ncomms15333, 2017.
Citation: https://doi.org/10.5194/egusphere-2023-52-RC3 - AC3: 'Reply on RC3', Fa lei Xu, 17 Apr 2023
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2023-52', Anonymous Referee #1, 08 Mar 2023
Using the station observations and multi reanalysis data, the authors investigated the possible influences of the previous NAO on the dust aerosols over northern China. Authors concluded that the boreal winter NAO has significant impacts on the following spring dust aerosols, particularly during the negative phase of the NAO. The thermal and dynamical processes relevant to the anomalous NAO on the circulation are analyzed, and it indicated that the impact of transient eddy fluxes transport plays important role in the formation of the dust aerosol events. I agree with the authors that the influence of previous NAO on dust aerosols in China cannot be ignored. And it is an important interdisciplinary issue that needs more attention and deep research. Overall the manuscript is well written and clear, and the figures are also appropriate and clear. However, there are some problems with this manuscript, and it cannot be accepted by ACP as it is now. Some specific comments or suggestions are listed as follows:
(1) Introduction: the review of the dust aerosol’s climate effect and the NAO’s impacts on the regional climate anomalies are a little repetitive and lengthy. Address and summary the major research progress of the present work.
(2) NAO index: There are lots of definitions of the NAOI, what is the advantage of the NAOI used, and whether the result is robust if other definitions are used. The authors need to further compare the different NAOI, and clarify whether the result is subject to the NAOI.
(3) The role of previous winter NAO on the following spring dust aerosols is discussed, however, as reported ENSO shows a significant role in determining the winter and spring climate anomalies over eastern China. it is of interest to further discuss whether the impacts of NAO on the aerosols are independent of ENSO.
(4) L218: prior to rather than previous to
(5) Line 34: The descriptions are confusing.
(6) In the upper troposphere, it is emphasized that both the jet stream and downward transmission of high-altitude wind speed momentum contribute to the formation of the dust aerosols, however, without a detailed physical explanation of the combined role the two.
(7) In the middle troposphere, the evolution of the trough-ridge system along with the occurrence of the dust aerosol events should be further analyzed. The involved physical process, particularly, which variable is more important in the process warranty further illustration.
(8) There are lots of clerical errors, i.e.,
L306, should be 0.1 in and 0.2 in
L351, should be 35°-50°N, 70°-110°E
L356-360, lengthy and repetition
L377, should be prior to
L404, should be 30°-60°N, 105°-130°E
The authors should carefully check the whole manuscript.
(9) Figures 2, 4, 7, 10, 13, without clarification of the axis, Figure 3, without units.Citation: https://doi.org/10.5194/egusphere-2023-52-RC1 - AC1: 'Reply on RC1', Fa lei Xu, 17 Apr 2023
-
RC2: 'Comment on egusphere-2023-52', Anonymous Referee #2, 11 Mar 2023
General comments:
This study investigated the relationship between the boreal winter North Atlantic Oscillation (NAO) and the spring dust events (DEs) over North China (30-40°N, 105-120°E) during 1980-2020. The authors demonstrated that there is a significant negative relationship between the boreal winter NAO index and the late spring DAs in the North China. The synoptic cause of such relation is characterized as the changes in the tropospheric synoptic situation in the Ural Mountains, DAs source regions in China, and North China during the DEs under the modulation of the NAO negative signal. Further, evolution mechanism of abnormal atmospheric circulation affected by the NAO negative signal is explained by the transient eddy fluxes transport, thermal wind principle, and the quasi-geostrophic theory.
This paper is very meaningful, and a great quantity of previous work has been summarized and cited. The results of this study are interesting and useful to deepen our understanding of formation mechanism of the DEs in east Asia. I would like to recommend this manuscript should be accepted subject to minor revision, for this study fit well with the scope of Atmospheric Chemistry and Physics.
Specific comments are as follows.
- Line 85: “it is of important practical”. I suggest deleting “of” in the sentence.
- Line 155,450,471: “mechanisms”. I suggest revising it as “mechanism” and pay more attention to tenses of verbs.
- Line 140: “the DEs in northern China regions”. I suggest deleting “regions”.
- Line 192-195: The full name of the ERA5 reanalysis datasets is not correct.
- Line 208-210: What is the exact definition of selection criteria for the NAO abnormal years? Please describe it specifically.
- Line 259: “in DJF, JFM, and FMA in the early period”. I suggest revising it as “in previous DJF, JFM, and FMA”.
- Line 278: Figure 3, units needed.
- Line 310-311: Information of the 27 DEs seems not enough. It is suggested to list 27 DEs and the years in which these DEs occurred in a table, which may be easier for readers to understand better.
- Line 316-321: It is not clear how the 9 DEs are selected from the climate scale and the weather scale. It is better to be described in detail by means of figures or tables.
- Line 404: Should be (30°-60°N, 105-130°E).
- Line 579,603: The citation of references (Gary, 2011) should be revised as (Gary, 2012).
- Line 728-730: The author also mentioned that both NAO and ENSO play important role in the occurrence and development of DEs in China, and the research on such synergistic effects is relatively little yet. Have you got some preliminary results? Or the authors could conduct research on this issue in the next step of work.
- The labels in some figures (Figure 7, Figure 10-13) should be further enlarged, since they are rather small to distinguish.
Citation: https://doi.org/10.5194/egusphere-2023-52-RC2 - AC2: 'Reply on RC2', Fa lei Xu, 17 Apr 2023
-
RC3: 'Comment on egusphere-2023-52', Anonymous Referee #3, 11 Mar 2023
This study investigates the impacts of North Atlantic Oscillation (NAO) on spring dust aerosols over North China based on station observation data and multi reanalysis datasets. They found that late spring dust aerosols are negatively correlated with the boreal winter NAO index. They further illustrate that the changes in transient eddy momentum over the dust source region the Ural Mountains could explain the relative high spring dust levels following the negative winter NAO events. The topic is interesting and method is sound. I recommend it can be published after addressing my minor comments below.
My main comment is about how is the station observation of dust events and reanalysis data connected. Many results of this study are based on MERRA-2 dust column mass. However, how the MERRA-2 captures the dust events over the 41-years, especially those related to the negative NAO, comparing to the surface observation should be examined. Also, the dust events are separated into dust storm, blowing dust and floating dust. Are they show the same relationship with NAO?
Minor comments:
In the abstract, the correlation coefficient between the boreal winter NAO index and the late spring DAs in the North China is -0.39, but I did not find thin value in the main text (probably in line 260).
Line 54: Studies also reported that the dust can interact with winds in China through its radiative effect, which further weakens winds during weak wind years in winter over North China (e.g., Yang et al., 2017).
The authors explain the impacts of NAO on dust in North China through changes in energy and large-scale circulation. But they also showed that NAO can cause unusual rainy climate, which can influence the wet removal of dust. How this effect considered in the study.
The mechanism of the NAO impacts may not be only limited to dust in China, but also dust over the central Asia and North Africa. The authors could add some discussion about it.
Reference:
Yang, Y., Russell, L. M., Lou, S., Liao, H., Guo, J., Liu, Y., Singh, B., and Ghan, S. J.: Dust-wind interactions can intensify aerosol pollution over eastern China, Nat. Commun., 8, 15333, https://doi.org/10.1038/ncomms15333, 2017.
Citation: https://doi.org/10.5194/egusphere-2023-52-RC3 - AC3: 'Reply on RC3', Fa lei Xu, 17 Apr 2023
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Yan Li
Falei Xu
Juan Feng
Mengying Du
Wenjun Song
Chao Li
Wenjing Zhao
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(4077 KB) - Metadata XML