Whether recent Arctic sea ice loss is responsible for recent severe winters over mid-latitude continents has emerged as a major debate among climate scientists owing to short records of observations and large internal...Whether recent Arctic sea ice loss is responsible for recent severe winters over mid-latitude continents has emerged as a major debate among climate scientists owing to short records of observations and large internal variability in mid- and high-latitudes. In this study, the authors divide the evolution of autumn Arctic sea ice extent during 1979–2014 into three epochs, 1979–1986（high）, 1987–2006（moderate）, and 2007–2014（low）, using a regime shift identification method. The authors then compare the associations between autumn Arctic sea ice and winter climate anomalies over central and eastern Eurasia for the three epochs with a focus on extreme events. The results show robust and detectable signals of Arctic sea ice loss in weather and climate over western Siberia and East Asia. Associated with sea ice loss, the latitude（speed） of the jet stream shifts southward（reduces）,the wave extent amplifies, and blocking high events increase over the Ural Mountains, leading to increased frequency of cold air outbreaks extending from central Asia to northeast China. These associations bear a high degree of similarity to the observed atmospheric anomalies during the low sea ice epoch. By contrast, the patterns of atmospheric anomalies for the high sea ice epoch are different from those congruent with sea ice variability, which is related to the persistent negative phase of the Arctic Oscillation.展开更多
In order to archive, quality control and disseminate a large variety of marine data in a marine data exchange platfonn, a marine XML has been developed to encapsulate marine data, which provides an efficient means to ...In order to archive, quality control and disseminate a large variety of marine data in a marine data exchange platfonn, a marine XML has been developed to encapsulate marine data, which provides an efficient means to store, transfer and display marine data. This paper first presents the details of the main marine XML elements and then gives an example showing how to transform CTD-observed data into Marine XML format, which illustrates the XML encapsulation process of marine observed data.展开更多
The frequent and rapid onset of flash drought poses a serious threat to agriculture and ecosystems.Detecting human influences on flash droughts and estimating their future risks under climate change have attracted gre...The frequent and rapid onset of flash drought poses a serious threat to agriculture and ecosystems.Detecting human influences on flash droughts and estimating their future risks under climate change have attracted great attention.Focusing on a record-breaking flash drought event in the southeastern coastal region of China in summer 2020,the authors found that the suppression of convective precipitation and high temperature caused by the persistent high geopotential height anomalies and land-atmosphere dry coupling were important reasons for the rapid onset and strong intensity of the flash drought.Event attribution analysis with the latest CMIP6 data showed that anthropogenic climate change has not only increased the likelihood of an onset speed and intensity like those of the 2020 flash drought event,by about 93%±20%and 18%±15%,respectively,but also increased the chance of their simultaneous occurrence,by about 86%±38%,according to their joint probability distribution.Under a business-as-usual future scenario(SSP2-4.5),the likelihood of such an onset speed,intensity,and their simultaneous occurrence will further increase,by 85%±33%,49%±8%,and 81%±48%,respectively,as compared with current climate conditions.This study highlights the importance of anthropogenic climate change for accelerating and intensifying flash drought in the southeastern coastal region of China.展开更多
Vegetation is the main component of the terrestrial ecosystem and plays a key role in global climate change. Remotely sensed vegetation indices are widely used to detect vegetation trends at large scales. To understan...Vegetation is the main component of the terrestrial ecosystem and plays a key role in global climate change. Remotely sensed vegetation indices are widely used to detect vegetation trends at large scales. To understand the trends of vegetation cover, this research examined the spatial-temporal trends of global vegetation by employing the normalized difference vegetation index(NDVI) from the Advanced Very High Resolution Radiometer(AVHRR) Global Inventory Modeling and Mapping Studies(GIMMS) time series(1982–2015). Ten samples were selected to test the temporal trend of NDVI, and the results show that in arid and semi-arid regions, NDVI showed a deceasing trend, while it showed a growing trend in other regions. Mann-Kendal(MK) trend test results indicate that 83.37% of NDVI pixels exhibited positive trends and that only 16.63% showed negative trends(P < 0.05) during the period from 1982 to 2015. The increasing NDVI trends primarily occurred in tree-covered regions because of forest growth and re-growth and also because of vegetation succession after a forest disturbance. The increasing trend of the NDVI in cropland regions was primarily because of the increasing cropland area and the improvement in planting techniques. This research describes the spatial vegetation trends at a global scale over the past 30+ years, especially for different land cover types.展开更多
Recently, study in past trends of climate variables gained significant consideration because of its contribution in adaptions and mitigation strategies for potential future changes in climate, primarily in the area of...Recently, study in past trends of climate variables gained significant consideration because of its contribution in adaptions and mitigation strategies for potential future changes in climate, primarily in the area of water resource management. Future interannual and inter-seasonal variations in maximum and minimum temperature may bring significant changes in hydrological systems and affect regional water resources. The present study has been performed to observe past(1970-2010) as well as future(2011-2100)spatial and temporal variability in temperature(maximum and minimum) over selected stations of Sutlej basin located in North-Western Himalayan region in India. The generation of future time series of temperature data at different stations is done using statistical downscaling technique. The nonparametric test methods, modified Mann-Kendall test and Cumulative Sum chart are used for detecting monotonic trend and sequential shift in time series of maximum and minimum temperature. Sen's slope estimator test is used to detect the magnitude of change over a period of time on annual and seasonal basis. The cooling experienced in annual TMax and TMin at Kasol in past(1970-2010) would be replaced by warming in future as increasing trends are detected in TMax during 2020 s and 2050 s and in TMin during 2020 s, 2050 s and 2080 s under A1 B and A2 scenarios. Similar results of warming are also predicted at Sunnifor annual TMin in future under both scenarios which witnessed cooling during 1970-2010. The rise in TMin at Rampur is predicted to be continued in future as increasing trends are obtained under both the scenarios. Seasonal trend analysis reveals large variability in trends of TMax and TMin over these stations for the future periods.展开更多
This study focuses on the spatial and temporal distribution characteristics of mesoscale eddies in the South China Sea(SCS). An automatic eddy detection method,based on the geometry of velocity vectors,was adopted to ...This study focuses on the spatial and temporal distribution characteristics of mesoscale eddies in the South China Sea(SCS). An automatic eddy detection method,based on the geometry of velocity vectors,was adopted to obtain an eddy dataset from 21 years of satellite altimeter data. Analysis revealed that the number of anticyclonic eddies was nearly equal to cyclonic eddies; in the SCS,cyclonic eddies are generally stronger than anticyclonic eddies and anticyclonic eddies are larger and longer-lived than cyclonic eddies. Anticyclonic eddies tend to survive longer in the spring and summer,while cyclonic eddies have longer lifetimes in the autumn and winter. The characteristics and seasonal variations of eddies in the SCS are strongly related to variations in general ocean circulation,in the homogeneity of surface wind stress,and in the unevenness of bottom topography in the SCS. The spatial and temporal variation of mesoscale eddies in the SCS could,therefore,be an important index for understanding local hydrodynamics and regional climate change.展开更多
Soil moisture droughts can trigger abnormal changes of material and energy cycles in the soil-vegetation-atmosphere system,leading to important effects on local ecosystem,weather,and climate.Drought detection and unde...Soil moisture droughts can trigger abnormal changes of material and energy cycles in the soil-vegetation-atmosphere system,leading to important effects on local ecosystem,weather,and climate.Drought detection and understanding benefit disaster alleviation,as well as weather and climate predictions based on the understanding the land-atmosphere interactions.We thus simulated soil moisture using land surface model CLM3.5 driven with observed climate in China,and corrected wet bias in soil moisture simulations via introducing soil porosity parameter into soil water parameterization scheme.Then we defined soil moisture drought to quantify spatiotemporal variability of droughts.Over the period from 1951 to 2008,40%of months(to the sum of 12×58)underwent droughts,with the average area of 54.6%of total land area of China's Mainland.The annual monthly drought numbers presented a significant decrease in arid regions,but a significant increase in semi-arid and semi-humid regions,a decrease in humid regions but not significant.The Mainland as a whole experienced an increasing drought trend,with77.3%of areal ratio of decrease to increase.The monthly droughts in winter were the strongest but the weakest in summer,impacting 54.3%and 8.4%total area of the Mainland,respectively.The drought lasting three months or more occurred mainly in the semi-arid and semi-humid regions,with probability>51.7%,even>77.6%,whereas those lasting 6 and 12 months or more impacted mainly across arid and semi-arid regions.展开更多
The toxic gases,such as CO and NO,are highly dangerous to human health and even cause the death of person and animals in a tiny amount.Therefore,it is very necessary to develop the toxic gas sensors that can instantly...The toxic gases,such as CO and NO,are highly dangerous to human health and even cause the death of person and animals in a tiny amount.Therefore,it is very necessary to develop the toxic gas sensors that can instantly monitor these gases.In this work,we have used the first-principles calculations to investigate adsorption of gases on defective graphene nanosheets to seek a suitable material for CO sensing.Result indicates that the vancancy graphene can not selectivly sense CO from air,because O2 in air would disturb the sensing signals of graphene for CO,while the nitrogen-doped graphene is an excellent candidate for selectivly sensing CO from air,because only CO can be chemisorbed on the pyridinic-like N-doped graphene accompanying with a large charge transfer,which can serve as a useful electronic signal for CO sensing.Even in the environment with NO,the N-doped graphene can also detect CO selectively.Therefore,the N-doped graphene is an excellent material for selectively sensing CO,which provides useful information for the design and fabrication of the CO sensors.展开更多
基金supported by the National Natural Science Foundation of China[grant number 41176169]the National Basic Research Program of China[grant number 2011CB309704]
文摘Whether recent Arctic sea ice loss is responsible for recent severe winters over mid-latitude continents has emerged as a major debate among climate scientists owing to short records of observations and large internal variability in mid- and high-latitudes. In this study, the authors divide the evolution of autumn Arctic sea ice extent during 1979–2014 into three epochs, 1979–1986（high）, 1987–2006（moderate）, and 2007–2014（low）, using a regime shift identification method. The authors then compare the associations between autumn Arctic sea ice and winter climate anomalies over central and eastern Eurasia for the three epochs with a focus on extreme events. The results show robust and detectable signals of Arctic sea ice loss in weather and climate over western Siberia and East Asia. Associated with sea ice loss, the latitude（speed） of the jet stream shifts southward（reduces）,the wave extent amplifies, and blocking high events increase over the Ural Mountains, leading to increased frequency of cold air outbreaks extending from central Asia to northeast China. These associations bear a high degree of similarity to the observed atmospheric anomalies during the low sea ice epoch. By contrast, the patterns of atmospheric anomalies for the high sea ice epoch are different from those congruent with sea ice variability, which is related to the persistent negative phase of the Arctic Oscillation.
基金funds of Ocean University of China Research Initiation Grant and the National 908 Project entitled ‘Marine Information Exchange and Integration Technology Based on XML’ (No 908-03-01-07)
文摘In order to archive, quality control and disseminate a large variety of marine data in a marine data exchange platfonn, a marine XML has been developed to encapsulate marine data, which provides an efficient means to store, transfer and display marine data. This paper first presents the details of the main marine XML elements and then gives an example showing how to transform CTD-observed data into Marine XML format, which illustrates the XML encapsulation process of marine observed data.
基金supported by the National Natural Science Foundation of China[grant number 41875105]the National Key R&D Program of China[grant number 2018YFA0606002]the Natural Science Foundation of Jiangsu Province for Distinguished Young Scholars[grant number BK20211540]。
文摘The frequent and rapid onset of flash drought poses a serious threat to agriculture and ecosystems.Detecting human influences on flash droughts and estimating their future risks under climate change have attracted great attention.Focusing on a record-breaking flash drought event in the southeastern coastal region of China in summer 2020,the authors found that the suppression of convective precipitation and high temperature caused by the persistent high geopotential height anomalies and land-atmosphere dry coupling were important reasons for the rapid onset and strong intensity of the flash drought.Event attribution analysis with the latest CMIP6 data showed that anthropogenic climate change has not only increased the likelihood of an onset speed and intensity like those of the 2020 flash drought event,by about 93%±20%and 18%±15%,respectively,but also increased the chance of their simultaneous occurrence,by about 86%±38%,according to their joint probability distribution.Under a business-as-usual future scenario(SSP2-4.5),the likelihood of such an onset speed,intensity,and their simultaneous occurrence will further increase,by 85%±33%,49%±8%,and 81%±48%,respectively,as compared with current climate conditions.This study highlights the importance of anthropogenic climate change for accelerating and intensifying flash drought in the southeastern coastal region of China.
基金Under the auspices of National Natural Science Foundation of China(No.41771179,41871103,41771138)the National Key Research and Development Project(No.2016YFA0602301)
文摘Vegetation is the main component of the terrestrial ecosystem and plays a key role in global climate change. Remotely sensed vegetation indices are widely used to detect vegetation trends at large scales. To understand the trends of vegetation cover, this research examined the spatial-temporal trends of global vegetation by employing the normalized difference vegetation index(NDVI) from the Advanced Very High Resolution Radiometer(AVHRR) Global Inventory Modeling and Mapping Studies(GIMMS) time series(1982–2015). Ten samples were selected to test the temporal trend of NDVI, and the results show that in arid and semi-arid regions, NDVI showed a deceasing trend, while it showed a growing trend in other regions. Mann-Kendal(MK) trend test results indicate that 83.37% of NDVI pixels exhibited positive trends and that only 16.63% showed negative trends(P < 0.05) during the period from 1982 to 2015. The increasing NDVI trends primarily occurred in tree-covered regions because of forest growth and re-growth and also because of vegetation succession after a forest disturbance. The increasing trend of the NDVI in cropland regions was primarily because of the increasing cropland area and the improvement in planting techniques. This research describes the spatial vegetation trends at a global scale over the past 30+ years, especially for different land cover types.
基金financial support in the form of fellowship provided by University Grant Commission (UGC), Government of India to Mr. Dharmaveer Singh as Research Fellow for carrying out the research
文摘Recently, study in past trends of climate variables gained significant consideration because of its contribution in adaptions and mitigation strategies for potential future changes in climate, primarily in the area of water resource management. Future interannual and inter-seasonal variations in maximum and minimum temperature may bring significant changes in hydrological systems and affect regional water resources. The present study has been performed to observe past(1970-2010) as well as future(2011-2100)spatial and temporal variability in temperature(maximum and minimum) over selected stations of Sutlej basin located in North-Western Himalayan region in India. The generation of future time series of temperature data at different stations is done using statistical downscaling technique. The nonparametric test methods, modified Mann-Kendall test and Cumulative Sum chart are used for detecting monotonic trend and sequential shift in time series of maximum and minimum temperature. Sen's slope estimator test is used to detect the magnitude of change over a period of time on annual and seasonal basis. The cooling experienced in annual TMax and TMin at Kasol in past(1970-2010) would be replaced by warming in future as increasing trends are detected in TMax during 2020 s and 2050 s and in TMin during 2020 s, 2050 s and 2080 s under A1 B and A2 scenarios. Similar results of warming are also predicted at Sunnifor annual TMin in future under both scenarios which witnessed cooling during 1970-2010. The rise in TMin at Rampur is predicted to be continued in future as increasing trends are obtained under both the scenarios. Seasonal trend analysis reveals large variability in trends of TMax and TMin over these stations for the future periods.
基金Supported by the National High Technology Research and Development Program of China(863 Program)(No.2013AA09A505)the National Natural Science Foundation of China(No.U1133001)the NSFC-Shandong Joint Fund for Marine Science Research Centers Grant(No.U1406401)
文摘This study focuses on the spatial and temporal distribution characteristics of mesoscale eddies in the South China Sea(SCS). An automatic eddy detection method,based on the geometry of velocity vectors,was adopted to obtain an eddy dataset from 21 years of satellite altimeter data. Analysis revealed that the number of anticyclonic eddies was nearly equal to cyclonic eddies; in the SCS,cyclonic eddies are generally stronger than anticyclonic eddies and anticyclonic eddies are larger and longer-lived than cyclonic eddies. Anticyclonic eddies tend to survive longer in the spring and summer,while cyclonic eddies have longer lifetimes in the autumn and winter. The characteristics and seasonal variations of eddies in the SCS are strongly related to variations in general ocean circulation,in the homogeneity of surface wind stress,and in the unevenness of bottom topography in the SCS. The spatial and temporal variation of mesoscale eddies in the SCS could,therefore,be an important index for understanding local hydrodynamics and regional climate change.
基金supported by the National Basic Research Program of China(Grant No.2012CB956202)the National Key Technology R&D Program of China(Grant Nos.2013BAC10B02,2012BAC22B04)the National Natural Science Foundation of China(Grant No.41105048)
文摘Soil moisture droughts can trigger abnormal changes of material and energy cycles in the soil-vegetation-atmosphere system,leading to important effects on local ecosystem,weather,and climate.Drought detection and understanding benefit disaster alleviation,as well as weather and climate predictions based on the understanding the land-atmosphere interactions.We thus simulated soil moisture using land surface model CLM3.5 driven with observed climate in China,and corrected wet bias in soil moisture simulations via introducing soil porosity parameter into soil water parameterization scheme.Then we defined soil moisture drought to quantify spatiotemporal variability of droughts.Over the period from 1951 to 2008,40%of months(to the sum of 12×58)underwent droughts,with the average area of 54.6%of total land area of China's Mainland.The annual monthly drought numbers presented a significant decrease in arid regions,but a significant increase in semi-arid and semi-humid regions,a decrease in humid regions but not significant.The Mainland as a whole experienced an increasing drought trend,with77.3%of areal ratio of decrease to increase.The monthly droughts in winter were the strongest but the weakest in summer,impacting 54.3%and 8.4%total area of the Mainland,respectively.The drought lasting three months or more occurred mainly in the semi-arid and semi-humid regions,with probability>51.7%,even>77.6%,whereas those lasting 6 and 12 months or more impacted mainly across arid and semi-arid regions.
基金supported by the National Basic Research Program of China(2011CB706900)the National Natural Science Foundation of China(91334203,21274011,21121064)+2 种基金the National High-Tech Research&Development Program of China(2013AA031901)the National Scientific Research Funding(ZZ1304)the Outstanding Talents Plans from BUCT
文摘The toxic gases,such as CO and NO,are highly dangerous to human health and even cause the death of person and animals in a tiny amount.Therefore,it is very necessary to develop the toxic gas sensors that can instantly monitor these gases.In this work,we have used the first-principles calculations to investigate adsorption of gases on defective graphene nanosheets to seek a suitable material for CO sensing.Result indicates that the vancancy graphene can not selectivly sense CO from air,because O2 in air would disturb the sensing signals of graphene for CO,while the nitrogen-doped graphene is an excellent candidate for selectivly sensing CO from air,because only CO can be chemisorbed on the pyridinic-like N-doped graphene accompanying with a large charge transfer,which can serve as a useful electronic signal for CO sensing.Even in the environment with NO,the N-doped graphene can also detect CO selectively.Therefore,the N-doped graphene is an excellent material for selectively sensing CO,which provides useful information for the design and fabrication of the CO sensors.
