In the northeastern(NE) Arabian Sea,the fluctuation in terrestrial and freshwater runoff directly depends on southwest monsoon(SWM) precipitation as well as the meltwater flux provided by Indus River.Therefore,analysi...In the northeastern(NE) Arabian Sea,the fluctuation in terrestrial and freshwater runoff directly depends on southwest monsoon(SWM) precipitation as well as the meltwater flux provided by Indus River.Therefore,analysis of multi-proxy spectral signatures was carried out to trace the high-resolution SWM periodicities and their influence on the productivity,regional sea level fluctuations and depositional processes in the NE Arabian Sea.The time series data of stable isotopes of oxygen(δ^18 O(G.ruber)).carbon(δ^13 C(G.ruber) and δ^13 C(org)) and nitrogen(δ^15 N).Total Organic Carbon(TOC),planktic-benthic foraminiferal ratio(P/B ratio) and>63 μm coarse fraction(CF) were used from two coastal sedimentary cores located offshore Saurashtra,NE Arabian Sea(Core SK-240/485 having 88 m water depth;Core GC/SK-240/496 having 174 m water depth).The REDFIT based spectral analysis recorded significant periodicities(>90% significance) in δ^18 0 time series centered at^1609,~667,~525,~296,~290 and^256 years.Further,the significant periodicities recorded in carbon isotopes time series(δ^13 C(G.ruber) and δ^13 C(org))centered at^681,~512,~471,~452,~438,~360,~292,~275,~269,~245 and^209 years.The significant periodicities in TOC include^471 and-322 years whereas δ^15 N time series recorded significant periodicity centered at-360 years.The significant periodicities in P/B ratio time series centered at^512,~388,~304,~250,~235,~217,~152,~139 and^135 years while CF recorded^268,~216,~209,~198,~188,~173 and^140 years significant periodicities.The observed periodicities in the multi-proxy record consist of similar cycles(within the radiocarbon dating error) which also natch with previously reported solar insolation influenced SWM and other global and regional cycles.Further,the stationarity of the data has been verified using wavelet analysis and shows similar periodicities as observed in REDFIT analysis.Thereafter,the depositional behaviour was studied using correlation analysis of the common periods of δ^18 0 time series of both the cores.The result suggests that the depositional behaviour was different for both the core sites during the early Holocene and became similar during the middle Holocene.The correlation analysis of Total Solar Index(TSI) with δ^18 O time series reveals a significant correlation with the core SK-240/485 whereas an insignificant correlation with the core GC/SK-240/496.These observations suggest that the solar insolation has been a leading factor responsible for the SWM trends during the Holocene which may have further influenced the productivity.regional sea level fluctuations and depositional conditions in the NE Arabian Sea.However,these trends are better preserved in shallow marine sediments as compared to the deeper marine sediments.展开更多
基于《中国三千年疫灾史料汇编》中民国卷的全国疫灾史料,提取整理出西南地区各县域逐年疫灾发生的时间序列并进行空间分布可视化。结合英国东英吉利大学(University of East Anglia)气候研究中心(Climatic Research Unit,CRU)提供的逐...基于《中国三千年疫灾史料汇编》中民国卷的全国疫灾史料,提取整理出西南地区各县域逐年疫灾发生的时间序列并进行空间分布可视化。结合英国东英吉利大学(University of East Anglia)气候研究中心(Climatic Research Unit,CRU)提供的逐月气温数据集CRU TS v.4.05,利用Mann-Kendall突变检验、Sen斜率、热点分析及相关分析等方法研究气温变化、疫灾事件以及两者之间的关联性。结果表明:(1)民国时期西南地区每年均有疫灾发生,共发生疫灾4170次,平均每年约发生110次;波及共计3256县次,平均每年约发生86县;民国后期疫灾程度严重,频次与县次均呈现波动上升趋势,具有同步性;(2)平均温度整体表现为波动上升,空间分布上自东南向西北方向逐级递减,绝大部分为逐年上升趋势;(3)疫灾频次与温度具有显著正相关,夏秋疫灾多发,冬季少发;空间上有75.16%的研究区疫灾累积年数与平均气温呈现正相关,说明高温环境有利于疫灾的流行。(4)气温突变和波动幅度对疫灾的发生具有显著的影响,气温波动幅度大时,疫灾发生较多。展开更多
利用云南省124站观测资料及CRU(Climatic Research Unit)高分辨率降水数据分析了我国西南周边地区的降水时空变化特征,并进一步对该地区夏、秋季节降水的周期、降水与季风活动的关系以及旱涝时期环流背景做出分析,以探讨其年代际变化的...利用云南省124站观测资料及CRU(Climatic Research Unit)高分辨率降水数据分析了我国西南周边地区的降水时空变化特征,并进一步对该地区夏、秋季节降水的周期、降水与季风活动的关系以及旱涝时期环流背景做出分析,以探讨其年代际变化的可能影响机制。结果表明,我国西南周边地区的降水空间分布随季节演变,西南地区处于降水量相对小值区,各季节降水量存在明显的年际变化以及年代际振荡特征。通过周期分析发现,研究区域夏、季秋季降水均存在明显的年代际尺度周期,近年来西南地区连续干旱很可能是由夏季和秋季的年代际尺度周期负位相配合造成,并且降水的减少与夏季风活动偏弱、季风持续时间偏短有关。夏季秋季少雨时期与多雨时期环流场存在显著差异,表现为少雨时期我国东部低层异常的偏北风,青藏高原附近高层异常的反气旋型环流,多雨时期则相反。展开更多
基金SERB-DST Project No.SR/FTP/ES-53/2013Council of Scientific and Industrial Research(CSIR)(Grant No.09/528/0022/2018/EMR-1)for the financial assistance in the form of fellowshipssupported by fast-track grant of SERB-DST under project No.SR/FTP/ES-53/2013
文摘In the northeastern(NE) Arabian Sea,the fluctuation in terrestrial and freshwater runoff directly depends on southwest monsoon(SWM) precipitation as well as the meltwater flux provided by Indus River.Therefore,analysis of multi-proxy spectral signatures was carried out to trace the high-resolution SWM periodicities and their influence on the productivity,regional sea level fluctuations and depositional processes in the NE Arabian Sea.The time series data of stable isotopes of oxygen(δ^18 O(G.ruber)).carbon(δ^13 C(G.ruber) and δ^13 C(org)) and nitrogen(δ^15 N).Total Organic Carbon(TOC),planktic-benthic foraminiferal ratio(P/B ratio) and>63 μm coarse fraction(CF) were used from two coastal sedimentary cores located offshore Saurashtra,NE Arabian Sea(Core SK-240/485 having 88 m water depth;Core GC/SK-240/496 having 174 m water depth).The REDFIT based spectral analysis recorded significant periodicities(>90% significance) in δ^18 0 time series centered at^1609,~667,~525,~296,~290 and^256 years.Further,the significant periodicities recorded in carbon isotopes time series(δ^13 C(G.ruber) and δ^13 C(org))centered at^681,~512,~471,~452,~438,~360,~292,~275,~269,~245 and^209 years.The significant periodicities in TOC include^471 and-322 years whereas δ^15 N time series recorded significant periodicity centered at-360 years.The significant periodicities in P/B ratio time series centered at^512,~388,~304,~250,~235,~217,~152,~139 and^135 years while CF recorded^268,~216,~209,~198,~188,~173 and^140 years significant periodicities.The observed periodicities in the multi-proxy record consist of similar cycles(within the radiocarbon dating error) which also natch with previously reported solar insolation influenced SWM and other global and regional cycles.Further,the stationarity of the data has been verified using wavelet analysis and shows similar periodicities as observed in REDFIT analysis.Thereafter,the depositional behaviour was studied using correlation analysis of the common periods of δ^18 0 time series of both the cores.The result suggests that the depositional behaviour was different for both the core sites during the early Holocene and became similar during the middle Holocene.The correlation analysis of Total Solar Index(TSI) with δ^18 O time series reveals a significant correlation with the core SK-240/485 whereas an insignificant correlation with the core GC/SK-240/496.These observations suggest that the solar insolation has been a leading factor responsible for the SWM trends during the Holocene which may have further influenced the productivity.regional sea level fluctuations and depositional conditions in the NE Arabian Sea.However,these trends are better preserved in shallow marine sediments as compared to the deeper marine sediments.
文摘基于《中国三千年疫灾史料汇编》中民国卷的全国疫灾史料,提取整理出西南地区各县域逐年疫灾发生的时间序列并进行空间分布可视化。结合英国东英吉利大学(University of East Anglia)气候研究中心(Climatic Research Unit,CRU)提供的逐月气温数据集CRU TS v.4.05,利用Mann-Kendall突变检验、Sen斜率、热点分析及相关分析等方法研究气温变化、疫灾事件以及两者之间的关联性。结果表明:(1)民国时期西南地区每年均有疫灾发生,共发生疫灾4170次,平均每年约发生110次;波及共计3256县次,平均每年约发生86县;民国后期疫灾程度严重,频次与县次均呈现波动上升趋势,具有同步性;(2)平均温度整体表现为波动上升,空间分布上自东南向西北方向逐级递减,绝大部分为逐年上升趋势;(3)疫灾频次与温度具有显著正相关,夏秋疫灾多发,冬季少发;空间上有75.16%的研究区疫灾累积年数与平均气温呈现正相关,说明高温环境有利于疫灾的流行。(4)气温突变和波动幅度对疫灾的发生具有显著的影响,气温波动幅度大时,疫灾发生较多。
文摘利用云南省124站观测资料及CRU(Climatic Research Unit)高分辨率降水数据分析了我国西南周边地区的降水时空变化特征,并进一步对该地区夏、秋季节降水的周期、降水与季风活动的关系以及旱涝时期环流背景做出分析,以探讨其年代际变化的可能影响机制。结果表明,我国西南周边地区的降水空间分布随季节演变,西南地区处于降水量相对小值区,各季节降水量存在明显的年际变化以及年代际振荡特征。通过周期分析发现,研究区域夏、季秋季降水均存在明显的年代际尺度周期,近年来西南地区连续干旱很可能是由夏季和秋季的年代际尺度周期负位相配合造成,并且降水的减少与夏季风活动偏弱、季风持续时间偏短有关。夏季秋季少雨时期与多雨时期环流场存在显著差异,表现为少雨时期我国东部低层异常的偏北风,青藏高原附近高层异常的反气旋型环流,多雨时期则相反。
