Taklamakan Desert(TD)has been characterized by numerous heatwaves and dust storms,leading to negative effects on societies and ecosystems at regional and global scales.However,the association between heatwaves and dus...Taklamakan Desert(TD)has been characterized by numerous heatwaves and dust storms,leading to negative effects on societies and ecosystems at regional and global scales.However,the association between heatwaves and dust storms is poorly known.In this study,we describe the association between heatwaves and dust events and propose a mechanism for such compound events in the TD.The results show that,from 1993 to 2022,the frequency and intensity of heatwaves in the TD have increased at a rate of 0.21 days year^(-1)and 0.02℃ year^(-1),respectively.More than 40% of heatwaves existed with dust events,which significantly lagged behind heatwaves.Mechanically,the higher the air temperature,the hotter and drier the soil,leading to more dust emissions in the TD.In high-occurrence heatwave years,a large-scale wave train of“cyclone-anticyclone-cyclone”in the northwest-southeast direction was found,with the anticyclone of which hovered over the TD region.The anomalous anticyclones favored the formation and maintenance of heatwaves,and subsequent anomalous cyclones in the wave train triggered strong dust events followed by heatwaves.With climate warming,the compound events of heatwave and dust storm are becoming bigger hazards threatening the socioeconomic and ecological security in the TD,the profound study of which is critical to understanding regional extreme responses.展开更多
Growing evidence indicates that extreme heat and rain may occur in succession within short time periods and cause greater impacts than individual events separated in time and space.Therefore,many studies have examined...Growing evidence indicates that extreme heat and rain may occur in succession within short time periods and cause greater impacts than individual events separated in time and space.Therefore,many studies have examined the impacts of compound hazard events on the social-ecological system at various scales.The definition of compound events is fundamental for such research.However,there are no existing studies that support the determination of time interval between individual events of a compound rainstorm and heatwave(CRH)event,which consists of two or more potentially qualifying component heatwave and rainstorm events.To address the deficiency in defining what individual events can constitute a CRH event,this study proposed a novel method to determine the maximum time interval for CRH events through the change in CRH event frequency with increasing time interval between individual events,using southern China as a case study.The results show that the threshold identified by the proposed method is reasonable.For more than 90%of the meteorological stations,the frequency of CRH events has reached a maximum when the time interval is less than or equal to the threshold.This study can aid in time interval selection,which is an important step for subsequent study of CRH events.展开更多
BACKGROUND： Previous studies of attentional control have focused primarily on pre-cue control of attentional cue and direction. OBJECTIVE： To measure the differences in electrical activity of brain cells while proce...BACKGROUND： Previous studies of attentional control have focused primarily on pre-cue control of attentional cue and direction. OBJECTIVE： To measure the differences in electrical activity of brain cells while processing pre-cue and post-cue compound stimuli, and to explore brain electrical activity during global and local processing of compound stimuli according to electroencephalogram （EEG） recordings. DESIGN, TIME AND SETTING： A within-subject design study was performed at the School of Psychology, State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, China from March to May 2006. PARTICIPANTS： A total of 30 healthy, undergraduate students, aged 17-24 years, comprising 12 males and 18 females, were voluntarily enrolled from Beijing Normal University. Subjects exhibited normal or corrected-to-normal visual acuity. No significant non signal wave drift was detected during testing. METHODS： A total of 30 subjects were subjected to pre-cue and post-cue compound stimulus processing using event-related potential and EEG recordings. MAIN OUTCOME MEASURES： Evoked potential was recorded in different brain regions utilizing event-related potential to observe hemispheric symmetry, cue consistency and global-local features. RESULTS： Pre-cue compound stimuli resulted in hemispheric asymmetry for early wave （N1） and late wave （P3） in anterior brain regions. Early- and late-wave induced hemispheric asymmetry for electrode points （O1, 02, P3, P4, Pz, F3, F4, F7, F8, Fz, FP1, FP2, T7, TS, C3, C4, and Cz） during processing of pre-cue compound stimuli （P 〈 0.05）. Post-cue compound stimuli did not induce hemispheric asymmetry of brain waves induced by the above-described electrode points. No significant differences in global and local responses were determined during processing of post-cue compound stimuli. Under pre-cue conditions, significant differences were observed in N1 and P3 in the above-mentioned electrode points （P 〈 0.05）. However, under post-cue conditions, no significant differences were observed in N1 and P3 using the above-mentioned electrode points. Significant differences in early waves （N1 and P1） using the above-mentioned electrode points were detected between anterior and posterior brain regions, regardless of consistent or inconsistent, large or small letters （P 〈 0.05）. CONCLUSION： Cue location effected mechanisms underlying global and local processing of compound stimuli. Pre- or post-cue conditions resulted in differences in hemispheric symmetry, cue consistency, and global and local features. Under pre-cue conditions, hemispheric dominance was detected in global and local processing following compound stimuli. Under post-cue conditions, hemispheric dominance was not determined.展开更多
使用淮河流域1981年至2020年的149个气象站点的气温和相对湿度数据,分析了流域暖季极端高温干旱复合事件(Compound Drought and Heat Events,CDHEs)的时空演变特征,并通过趋势分析和相关分析法探讨了CDHEs与气候和植被的关系。结果表明:...使用淮河流域1981年至2020年的149个气象站点的气温和相对湿度数据,分析了流域暖季极端高温干旱复合事件(Compound Drought and Heat Events,CDHEs)的时空演变特征,并通过趋势分析和相关分析法探讨了CDHEs与气候和植被的关系。结果表明:(1)CDHEs的发生日数在年代际尺度上呈现明显的增加趋势,并且范围扩大,频发区逐渐向淮河流域中西部移动;(2)在年际尺度上,CDHEs随时间序列呈显著的波动上升趋势,空间分布上以西北部为中心向四周递减。连续CDHEs事件呈年际变化,最大2至4天的连续事件存在波动,2019年达到高峰,并且在流域内零散或成片出现;(3)在月际尺度上,CDHEs的发生日数在6月最多,其次是5月、7月、9月和8月。淮河流域入汛前的旱情和入汛后的旱涝急转都容易导致CDHEs发生,而且随着月际变化向南移动;(4)CDHEs对水热条件和大气环流具有特别的敏感性。在850hPa反气旋和500hPa显著高压异常的控制下,高温、低湿、高蒸发和降水少的气候背景有利于淮河地区CDHEs的形成,尤其是在淮河中西部地区。因此,CDHEs的发生与气候变化密切相关;(5)CDHEs与植被生长也存在显著关系。CDHEs与GPP呈显著的负相关,而与NDVI呈显著的正相关,显著地区的土地类型以耕地和城乡、工矿、居民用地为主。GPP和NDVI的不同步可能是因为多种因素的非线性相互作用,而不仅仅是单一因素的影响。此外,对于GPP和NDVI来说,土壤含水量至关重要。总之,本文对淮河流域CDHEs的时空分布特征进行了深入研究,并探讨了其与气候和植被的关系。研究结果可以为该地区的气象灾害防御和生态环境保护提供科学依据和参考。展开更多
基金supported by the National Key Technologies R&D Program of China[grant number 2022YFC3002803]the National Science Fund for Distinguished Young Scholars[grant number 41925021].
基金supported by the National Natural Science Foundation of China(Grant Nos.41991231 and 91937302)the Fundamental Research Funds for the Central Universities(Grant No.lzujbky-2022-kb11)。
文摘Taklamakan Desert(TD)has been characterized by numerous heatwaves and dust storms,leading to negative effects on societies and ecosystems at regional and global scales.However,the association between heatwaves and dust storms is poorly known.In this study,we describe the association between heatwaves and dust events and propose a mechanism for such compound events in the TD.The results show that,from 1993 to 2022,the frequency and intensity of heatwaves in the TD have increased at a rate of 0.21 days year^(-1)and 0.02℃ year^(-1),respectively.More than 40% of heatwaves existed with dust events,which significantly lagged behind heatwaves.Mechanically,the higher the air temperature,the hotter and drier the soil,leading to more dust emissions in the TD.In high-occurrence heatwave years,a large-scale wave train of“cyclone-anticyclone-cyclone”in the northwest-southeast direction was found,with the anticyclone of which hovered over the TD region.The anomalous anticyclones favored the formation and maintenance of heatwaves,and subsequent anomalous cyclones in the wave train triggered strong dust events followed by heatwaves.With climate warming,the compound events of heatwave and dust storm are becoming bigger hazards threatening the socioeconomic and ecological security in the TD,the profound study of which is critical to understanding regional extreme responses.
基金funded by the Joint Funds of the National Natural Science Foundation of China(Grant No.U22B2011)the Ministry of Education and State Administration of Foreign Experts Aff airs,China(Grant No.BP0820003)the Key Laboratory of Environmental Change and Natural Disaster of Ministry of Education(2023-KF-13)。
文摘Growing evidence indicates that extreme heat and rain may occur in succession within short time periods and cause greater impacts than individual events separated in time and space.Therefore,many studies have examined the impacts of compound hazard events on the social-ecological system at various scales.The definition of compound events is fundamental for such research.However,there are no existing studies that support the determination of time interval between individual events of a compound rainstorm and heatwave(CRH)event,which consists of two or more potentially qualifying component heatwave and rainstorm events.To address the deficiency in defining what individual events can constitute a CRH event,this study proposed a novel method to determine the maximum time interval for CRH events through the change in CRH event frequency with increasing time interval between individual events,using southern China as a case study.The results show that the threshold identified by the proposed method is reasonable.For more than 90%of the meteorological stations,the frequency of CRH events has reached a maximum when the time interval is less than or equal to the threshold.This study can aid in time interval selection,which is an important step for subsequent study of CRH events.
基金the Planning Program Foundation of Application and Experimental Psychology of Beijing Key Laboratory from 2008 to 2009.No.JD100270541
文摘BACKGROUND： Previous studies of attentional control have focused primarily on pre-cue control of attentional cue and direction. OBJECTIVE： To measure the differences in electrical activity of brain cells while processing pre-cue and post-cue compound stimuli, and to explore brain electrical activity during global and local processing of compound stimuli according to electroencephalogram （EEG） recordings. DESIGN, TIME AND SETTING： A within-subject design study was performed at the School of Psychology, State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, China from March to May 2006. PARTICIPANTS： A total of 30 healthy, undergraduate students, aged 17-24 years, comprising 12 males and 18 females, were voluntarily enrolled from Beijing Normal University. Subjects exhibited normal or corrected-to-normal visual acuity. No significant non signal wave drift was detected during testing. METHODS： A total of 30 subjects were subjected to pre-cue and post-cue compound stimulus processing using event-related potential and EEG recordings. MAIN OUTCOME MEASURES： Evoked potential was recorded in different brain regions utilizing event-related potential to observe hemispheric symmetry, cue consistency and global-local features. RESULTS： Pre-cue compound stimuli resulted in hemispheric asymmetry for early wave （N1） and late wave （P3） in anterior brain regions. Early- and late-wave induced hemispheric asymmetry for electrode points （O1, 02, P3, P4, Pz, F3, F4, F7, F8, Fz, FP1, FP2, T7, TS, C3, C4, and Cz） during processing of pre-cue compound stimuli （P 〈 0.05）. Post-cue compound stimuli did not induce hemispheric asymmetry of brain waves induced by the above-described electrode points. No significant differences in global and local responses were determined during processing of post-cue compound stimuli. Under pre-cue conditions, significant differences were observed in N1 and P3 in the above-mentioned electrode points （P 〈 0.05）. However, under post-cue conditions, no significant differences were observed in N1 and P3 using the above-mentioned electrode points. Significant differences in early waves （N1 and P1） using the above-mentioned electrode points were detected between anterior and posterior brain regions, regardless of consistent or inconsistent, large or small letters （P 〈 0.05）. CONCLUSION： Cue location effected mechanisms underlying global and local processing of compound stimuli. Pre- or post-cue conditions resulted in differences in hemispheric symmetry, cue consistency, and global and local features. Under pre-cue conditions, hemispheric dominance was detected in global and local processing following compound stimuli. Under post-cue conditions, hemispheric dominance was not determined.
文摘使用淮河流域1981年至2020年的149个气象站点的气温和相对湿度数据,分析了流域暖季极端高温干旱复合事件(Compound Drought and Heat Events,CDHEs)的时空演变特征,并通过趋势分析和相关分析法探讨了CDHEs与气候和植被的关系。结果表明:(1)CDHEs的发生日数在年代际尺度上呈现明显的增加趋势,并且范围扩大,频发区逐渐向淮河流域中西部移动;(2)在年际尺度上,CDHEs随时间序列呈显著的波动上升趋势,空间分布上以西北部为中心向四周递减。连续CDHEs事件呈年际变化,最大2至4天的连续事件存在波动,2019年达到高峰,并且在流域内零散或成片出现;(3)在月际尺度上,CDHEs的发生日数在6月最多,其次是5月、7月、9月和8月。淮河流域入汛前的旱情和入汛后的旱涝急转都容易导致CDHEs发生,而且随着月际变化向南移动;(4)CDHEs对水热条件和大气环流具有特别的敏感性。在850hPa反气旋和500hPa显著高压异常的控制下,高温、低湿、高蒸发和降水少的气候背景有利于淮河地区CDHEs的形成,尤其是在淮河中西部地区。因此,CDHEs的发生与气候变化密切相关;(5)CDHEs与植被生长也存在显著关系。CDHEs与GPP呈显著的负相关,而与NDVI呈显著的正相关,显著地区的土地类型以耕地和城乡、工矿、居民用地为主。GPP和NDVI的不同步可能是因为多种因素的非线性相互作用,而不仅仅是单一因素的影响。此外,对于GPP和NDVI来说,土壤含水量至关重要。总之,本文对淮河流域CDHEs的时空分布特征进行了深入研究,并探讨了其与气候和植被的关系。研究结果可以为该地区的气象灾害防御和生态环境保护提供科学依据和参考。
