The interannual variability in precipitation during the pre-rainy season(PRS) in South China is significantly correlated with Eurasian snow cover. This study elucidates the distinct mechanisms by which Eurasian snow c...The interannual variability in precipitation during the pre-rainy season(PRS) in South China is significantly correlated with Eurasian snow cover. This study elucidates the distinct mechanisms by which Eurasian snow cover anomalies in March influence precipitation during the early(pre-monsoon) and late(post-monsoon) PRS. In the early PRS, anomalous snow cover in the western region of Eastern Europe(WEE) triggers a southeastward-propagating wave train that impacts Central Asia.The teleconnection pattern induces anomalous cyclonic circulation in Central Asia, which reinforces the midlatitude zonal wind,contributing to the zonal wind wave train pattern towards East Asia. As a result, the East Asian subtropical westerly jet and the western North Pacific subtropical high are enhanced, and the related upper-level divergence, ascending motion, and moisture convergence in South China are intensified, collectively promoting precipitation there. In contrast, during the late PRS, increased snow cover across the eastern sector of Eastern Europe(EEE) and the region east of Lake Baikal(ELB) inhibit South China's precipitation. The wave pattern associated with the EEE(ELB) snow anomaly propagates southeastwards(southwards) to lower latitudes, intensifying the western North Pacific subtropical high. Furthermore, the perturbation stemming from the ELB region induces negative geopotential height anomalies aloft and amplifies the baroclinic anticyclone over the western Pacific. This resulted in prevailing subsidence over South China, which in turn suppresses precipitation during the late PRS. Numerical experiments corroborate the observed circulation adjustments and precipitation responses to snow cover anomalies in the two periods, lending credence to the proposed mechanisms.展开更多
Based on the NCEP DOE AMIP II daily reanalysis data （1979-2005）, the evolution of the East Asia/Pacific （EAP） teleconnection pattern during the pre-rainy period of South China is studied on the medium-range time s...Based on the NCEP DOE AMIP II daily reanalysis data （1979-2005）, the evolution of the East Asia/Pacific （EAP） teleconnection pattern during the pre-rainy period of South China is studied on the medium-range time scale. It is found that positive and negative EAP patterns share a similar generation process. In the middle and upper troposphere, Rossby wave packets emanating from the northeast Atlantic or Europe propagate toward East Asia along the Eurasian continent waveguide and finally give rise to the three anomaly centers of the EAP pattern over East Asia. Among the three anomaly centers, the western Pacific subtropical center appears the latest. Rossby wave packets propagate from the high latitude anomaly center toward the mid-latitude and the subtropical ones. The enhancement and maintenance of the subtropical anomaly center is closely associated with the subtropical jet waveguide and the incoming Rossby wave packets from the upstream. In the lower troposphere, Rossby wave packets emanate from the subtropical Asia toward East Asia. Positive and negative EAP patterns could not be regarded as ＂mirrors＂ to each other with simply reversed phase. For the positive pattern, the positive height anomaly center around the Scandinavia Peninsula keeps its strength and position during the mature period, and the Rossby wave packets thus propagate persistently toward East Asia, facilitating a longer mature time of the positive pattern. As for the formation of the negative EAP pattern, however, the incoming Rossby wave energy from the upstream contributes to both the enhancement and southeastward movement of the negative anomaly belt from the Yenisei River to the Bering Strait and the positive anomaly center around Mongolia. At the peak time, the two anomlous circulations are evolved into the Northeast Asia and the mid-latitude anomaly centers of the negative pattern, respectively. The energy dispersion of Rossby wave packets is relatively fast due to the predominant zonal circulation in the extratropics, causing a shorter mature period of the negative pattern. During the pre-rainy period of South China, the prevalence of the EAP pattern significantly affects the rainfall over the region south of the Yangtze River. The positive （negative） EAP pattern tends to cause positive （negative） precipitation anomalies in that region. This is different from the earlier research findings based on monthly mean data.展开更多
With the acceleration of urbanization in South China, rainstorms and floods are threatening the safety of people in urban areas. The 11 April 2019(4·11 hereafter)rainstorm in Shenzhen City was a typical pre-rainy...With the acceleration of urbanization in South China, rainstorms and floods are threatening the safety of people in urban areas. The 11 April 2019(4·11 hereafter)rainstorm in Shenzhen City was a typical pre-rainy season rainstorm that caused great damage, yet such pre-rainy season events have not attracted sufficient attention in research.Risk perception of the public may indirectly affect their disaster preparedness, which is important for disaster management. In this study, we conducted a questionnaire survey that considered demographic factors and the level of risk perception, knowledge of risk, impact of the 4·11 rainstorm event on public risk perception, and degree of trust in the government. We used a two-factor model of risk perception to evaluate the factors that influenced public risk perception of the 4·11 rainstorm in Shenzhen. The main conclusions are: The 4·11 rainstorm improved public awareness of both risk and impact through the medium term, but the public’s perceived low probability of disaster occurrence and lack of knowledge of the pre-rainy season rainstorm phenomenon led to serious losses during this event. Although the public has high trust in the Shenzhen government, the management of rainstorm disasters in the pre-rainy season needs to be further improved.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 42365004)the Natural Science Foundation of Guangxi Province(GrantNos. 2024GXNSFAA010211 & 2023GXNSFAA026511)the Research Foundation for Advanced Talents of Nanning Normal University。
文摘The interannual variability in precipitation during the pre-rainy season(PRS) in South China is significantly correlated with Eurasian snow cover. This study elucidates the distinct mechanisms by which Eurasian snow cover anomalies in March influence precipitation during the early(pre-monsoon) and late(post-monsoon) PRS. In the early PRS, anomalous snow cover in the western region of Eastern Europe(WEE) triggers a southeastward-propagating wave train that impacts Central Asia.The teleconnection pattern induces anomalous cyclonic circulation in Central Asia, which reinforces the midlatitude zonal wind,contributing to the zonal wind wave train pattern towards East Asia. As a result, the East Asian subtropical westerly jet and the western North Pacific subtropical high are enhanced, and the related upper-level divergence, ascending motion, and moisture convergence in South China are intensified, collectively promoting precipitation there. In contrast, during the late PRS, increased snow cover across the eastern sector of Eastern Europe(EEE) and the region east of Lake Baikal(ELB) inhibit South China's precipitation. The wave pattern associated with the EEE(ELB) snow anomaly propagates southeastwards(southwards) to lower latitudes, intensifying the western North Pacific subtropical high. Furthermore, the perturbation stemming from the ELB region induces negative geopotential height anomalies aloft and amplifies the baroclinic anticyclone over the western Pacific. This resulted in prevailing subsidence over South China, which in turn suppresses precipitation during the late PRS. Numerical experiments corroborate the observed circulation adjustments and precipitation responses to snow cover anomalies in the two periods, lending credence to the proposed mechanisms.
基金Supported jointly by the 973 Project under Grant No. 2006CB403601the National Natural Science Foundation of Chinaunder Grant Nos. 40523001 and 40575024
文摘Based on the NCEP DOE AMIP II daily reanalysis data （1979-2005）, the evolution of the East Asia/Pacific （EAP） teleconnection pattern during the pre-rainy period of South China is studied on the medium-range time scale. It is found that positive and negative EAP patterns share a similar generation process. In the middle and upper troposphere, Rossby wave packets emanating from the northeast Atlantic or Europe propagate toward East Asia along the Eurasian continent waveguide and finally give rise to the three anomaly centers of the EAP pattern over East Asia. Among the three anomaly centers, the western Pacific subtropical center appears the latest. Rossby wave packets propagate from the high latitude anomaly center toward the mid-latitude and the subtropical ones. The enhancement and maintenance of the subtropical anomaly center is closely associated with the subtropical jet waveguide and the incoming Rossby wave packets from the upstream. In the lower troposphere, Rossby wave packets emanate from the subtropical Asia toward East Asia. Positive and negative EAP patterns could not be regarded as ＂mirrors＂ to each other with simply reversed phase. For the positive pattern, the positive height anomaly center around the Scandinavia Peninsula keeps its strength and position during the mature period, and the Rossby wave packets thus propagate persistently toward East Asia, facilitating a longer mature time of the positive pattern. As for the formation of the negative EAP pattern, however, the incoming Rossby wave energy from the upstream contributes to both the enhancement and southeastward movement of the negative anomaly belt from the Yenisei River to the Bering Strait and the positive anomaly center around Mongolia. At the peak time, the two anomlous circulations are evolved into the Northeast Asia and the mid-latitude anomaly centers of the negative pattern, respectively. The energy dispersion of Rossby wave packets is relatively fast due to the predominant zonal circulation in the extratropics, causing a shorter mature period of the negative pattern. During the pre-rainy period of South China, the prevalence of the EAP pattern significantly affects the rainfall over the region south of the Yangtze River. The positive （negative） EAP pattern tends to cause positive （negative） precipitation anomalies in that region. This is different from the earlier research findings based on monthly mean data.
基金The study was supported by the National Key Research and Development Project(Grant No.2017YFC1503000).The authors would like to thank the reviewers for their valuable comments and the editors’help with this article.
文摘With the acceleration of urbanization in South China, rainstorms and floods are threatening the safety of people in urban areas. The 11 April 2019(4·11 hereafter)rainstorm in Shenzhen City was a typical pre-rainy season rainstorm that caused great damage, yet such pre-rainy season events have not attracted sufficient attention in research.Risk perception of the public may indirectly affect their disaster preparedness, which is important for disaster management. In this study, we conducted a questionnaire survey that considered demographic factors and the level of risk perception, knowledge of risk, impact of the 4·11 rainstorm event on public risk perception, and degree of trust in the government. We used a two-factor model of risk perception to evaluate the factors that influenced public risk perception of the 4·11 rainstorm in Shenzhen. The main conclusions are: The 4·11 rainstorm improved public awareness of both risk and impact through the medium term, but the public’s perceived low probability of disaster occurrence and lack of knowledge of the pre-rainy season rainstorm phenomenon led to serious losses during this event. Although the public has high trust in the Shenzhen government, the management of rainstorm disasters in the pre-rainy season needs to be further improved.
