the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 09 Apr 2024
Synergistic effects of previous winter NAO and ENSO on the spring dust activities in North China
Abstract. Dust plays an important role in influencing global weather and climate via impacting the Earth's radiative balance. Based on the atmospheric and oceanic datasets during 1980–2022, the impacts of preceding winter North Atlantic Oscillation (NAO) and El Niño-Southern Oscillation (ENSO) on the following spring dust activities over North China are explored. It is found that both NAO and ENSO exert significant effects in influencing the dust activities over North China, particularly during their negative phases. A synergistic influence on the dust activities in North China is observed when both NAO and ENSO are in negative phase, with their combined impacts exceeding that of either factor alone. The previous winter NAO exhibits significant impacts on the sea surface temperatures (SST) in the North Atlantic, associating with an anomalous SST tripole pattern. Owing to the persistence of SST, these anomalies can extend into the following spring, when anomalous atmospheric teleconnection wave trains would be induced, thereby influencing the dust activities in North China. ENSO, on the one hand, directly impacts dust activities in North China by modulating the circulation in the Western North Pacific (WNP). Moreover, ENSO enhances the NAO's effect on the North Atlantic SST, explaining their synergistic effects on the dust activities over North China. This study explains the combined role of NAO and ENSO on the dust weather over North China, providing one season ahead signals for the forecast of spring dust activities in North China.
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RC1: 'Comment on egusphere-2024-955', Anonymous Referee #1, 22 Apr 2024
General comments
This study investigated the impacts of preceding boreal winter North Atlantic Oscillation (NAO) and El Ni?o-Southern Oscillation (ENSO) on the following spring dust activities over North China during 1980-2022. The authors demonstrated that the significant impacts of NAO and ENSO on the dust activities over North China is only manifested in the negative phases, and discussed the physical mechanism involved to illustrate why the negative phases of NAO and ENSO show a synergistic effect on the following dust events in North China. The message is conveyed clearly and the topic is interesting. The results of this study provide an insight to further understand the dust activities over North China. The conclusions are substantiated based on composite analyses. If published, this work could serve as a valuable reference for dust weather. However, it needs to be minor revised before accepted this paper for publication in ACP with addressing those comments listed below:
Specific comments are as follows:
1.The NAO is a large-scale seesaw in atmospheric mass between the subtropical high and the polar low. It is the dominant mode of atmospheric circulation variability in the North Atlantic sector throughout the year. The definition of the NAO index derived using EOF is commonly employed to depict the variation of NAO. However, the SLP difference between 35°N and 65°N within the Atlantic section is used to define the NAO index. A full comparison of the NAO index is necessary to establish the robustness of result.2.The authors focus on the relationship between preceding winter NAO and ENSO and dust weather in late spring. The introduction mentions that “the impacts of winter NAO and ENSO on the climate in China is more pronounced” by citing results from previous work. However, it is unclear whether the cross-seasonal impacts also apply when exploring the relationship between NAO, ENSO and dust weather in North China. Therefore, it would be better to provide some references to explain why we should investigate the impacts of previous winter of NAO and ENSO on spring dust weather.
3. In the paper, the authors primarily discuss the effect of NAO and ENSO negative phases on the dust activities over North China. However, given the various phases combinations between these two factors, a more detailed explanation as to why only the negative-negative combinations are considered.
4. In Figures 1-2, the authors illustrate the relationship between NAO, ENSO and dust weather over North China through the spatial distribution of correlation coefficients, and that the relationship is only manifested when NAO and ENSO are in negative phases. A quantitative analysis is needed to further establish the robustness of the result.
5. From Fig 3 and Table 1, it is evident that there are two types when NAO and ENSO are in their negative phases: negative phases of the NAO and ENSO, and negative phases of the NAO and ENSO occurring separately (remove the years with concurrent negative phases of NAO and ENSO). Furthermore, the subsequent composite analyses in the study, focus on the cases with negative phases of the NAO and ENSO. The authors should explain why they have made this choice.
6. In Figs 4 c, f, and i, the variations in the near-surface wind field caused by anomalies of Siberian High, lead to dust emissions from the source areas. However, the depiction of the wind field anomalies appears unclear. It is recommended to modify the Figs to highlight the variations in the wind field.
7. In Table 2, the value of correlation coefficients between the previous winter NATI and spring NATI are similar in scenarios of ENSO- phase (when the negative phase of ENSO occurs alone) and NAO- & ENSO- phase (when the negative phases of both NAO and ENSO co-occur). However, if there exists a synergistic effect of NAO and ENSO on the dust weather, the correlation in the scenario where both NAO and ENSO negative phases co-occur should be higher than when the negative phases of NAO and ENSO occur separately. The authors should have provided a more detailed explanation to clarify this point.
8.The main mechanism for the impact of the winter NAO on the spring dust is the maintenance of the North Atlantic SST anomalies from winter to spring, consistent with previous findings (Chen et al. 2020; Wu and Chen 2020; Song et al. 2022). Several discussions could be added.
Song, L.-Y., et al, 2022: Distinct evolutions of haze pollution from winter to following spring over the North China Plain: Role of the North Atlantic sea surface temperature anomalies. Atmos. Chem. Phys., 22, 1669–1688.
Wu and Chen, 2020: What leads to persisting surface air temperature anomalies from winter to following spring over the mid-high latitude Eurasia?. Journal of Climate, 33, 5861-5883.
Chen et al. 2020: Strengthened connection between springtime North Atlantic Oscillation and North Atlantic tripole SST pattern since the late-1980s. Journal of Climate, 35(5), 2007-2022.9. There are lots of clerical errors, i.e.,
Line 17-18, sea surface temperatures (SST) in the North Atlantic
Line 220, with regard to the description of the graphs, there may be some errors that
“(b) and (d) As in (a) and (b) ” -> “(c) and (d) As in (a) and (b)”.
The authors should carefully check the whole manuscript.-
AC1: 'Reply on RC1', Fa lei Xu, 12 Jun 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-955/egusphere-2024-955-AC1-supplement.pdf
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AC1: 'Reply on RC1', Fa lei Xu, 12 Jun 2024
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RC2: 'Comment on egusphere-2024-955', Anonymous Referee #2, 27 May 2024
Using multi-reanalysis datasets, the authors investigated the effects of the previous winter NAO and ENSO on the spring dust aerosols over North China. The pronounced influence of NAO and ENSO on dust aerosols was predominantly observed during their negative phases. Furthermore, this analysis examined meteorological conditions, atmospheric dynamics, and wave energy transport, elucidating the synergistic impacts of these negative phases on subsequent dust activities. The findings enhance our understanding of the formation mechanisms of dust events in North China. I recommend that this manuscript be accepted after minor revisions, as this study fits well within the scope of Atmospheric Chemistry and Physics.
Specific comments are as follows:
- The study primarily utilizes MERRA-2 reanalysis data for analyzing dust activities over North China. It is essential to assess whether the MERRA-2 data accurately captures dust activities in North China. Please provide further details on the reliability of the reanalysis.
- The preceding role of NAO and ENSO on the spring dusty weather over North China is investigated, and it is of interest why the preceding role is focused. And whether their simultaneous role in the dust content is significant or not.
- Dust aerosols are important components of atmospheric aerosols, alongside other constituents such as sulfates, nitrogen oxides, black carbon, and so on. Why did the authors choose the dust aerosols in North China as the research objects to be discussed and studied? Please explain and justify this point.
- Line 36-37, “The Gobi Desert in East Asia, especially for the Mongolian Plateau and North China, is a major source of dust”. Whether the author is trying to express the meaning of Northern China here, Northern China and North China are two different meanings, please confirm and revise.
- Line 77-78, the authors mentioned that “NAO and ENSO often co-occur and have complex interactions”. As well as by citing previous work, the facts of a possible relationship between the two factors are enumerated. However, the authors have not thoroughly explored their relationship. It is suggested that further details be provided to enhance the understanding.
- In Figure 3 (a), it is notable that there is a point during the negative phase of the NAO that deviates from the majority of the points, potentially qualifying it as an outlier. If this point is removed from the sequence, it is important to verify whether the relationship between the NAO and dust aerosol content remains robust.
- In Figure 5, by describing the precipitation and humidity fields under different scenarios, the authors illustrate the synergistic effect of NAO and ENSO on dust activities in North China. However, the large values of the variables in the graphs do not seem to be well highlighted. Consider modifying the color-coded intervals to enhance the reader's understanding of the section.
Citation: https://doi.org/10.5194/egusphere-2024-955-RC2 -
AC2: 'Reply on RC2', Fa lei Xu, 12 Jun 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-955/egusphere-2024-955-AC2-supplement.pdf
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