The southeastern Indian Ocean is characterized by the warm barrier layer(BL)underlying the cool mixed layer water in austral winter.This phenomenon lasts almost half a year and thus provides a unique positive effect o...The southeastern Indian Ocean is characterized by the warm barrier layer(BL)underlying the cool mixed layer water in austral winter.This phenomenon lasts almost half a year and thus provides a unique positive effect on the upper mixed layer heat content through the entrainment processes at the base of the mixed layer,which has not been well evaluated due to the lack of proper method and dataset.Among various traditional threshold methods,here it is shown that the 5 m fixed depth difference can produce a reliable and accurate estimate of the entrainment heat flux(EHF)in this BL region.The comparison between the daily and monthly EHF warming indicates that the account for high-frequency EHF variability almost doubles the warming effect in the BL period,which can compensate for or even surpass the surface heat loss.This increased warming is a result of stronger relative rate of the mixed layer deepening and larger temperature differences between the mixed layer and its immediate below in the daily-resolving data.The interannual EHF shows a moderately increasing trend and similar variabilities to the Southern Annular Mode(SAM),likely because the mixed layer deepening under the positive SAM trend is accompanied by enhanced turbulent entrainment and thus increases the BL warming.展开更多
The relative contributions of atmospheric fluctuations on 6 h?2 d,2?8 d,and 8 d?1 month time scales to the changes in the air?sea fluxes,the SO circulation,and Antarctic sea ice are investigated.It was found that the ...The relative contributions of atmospheric fluctuations on 6 h?2 d,2?8 d,and 8 d?1 month time scales to the changes in the air?sea fluxes,the SO circulation,and Antarctic sea ice are investigated.It was found that the imposed forcing variability on the three time scales creates a significant increase in wind power input,and hence an increase of about 50%,97%,and 5%of eddy kinetic energy relative to the simulation driven by monthly forcing,respectively.Also,SO circulation and the strength of the upper cell of meridional overturning circulation become strengthened.These results indicate more dominant effects of atmospheric variability on the 2?8 d time scale on the SO circulation.Meanwhile,the 6 h?2 d(2?8 d)atmospheric variability causes an increase in the total sea-ice extent,area,and volume,by about 33%,30%,and 19%(17%,20%,and 25%),respectively,relative to those in the experiment forced by monthly atmospheric variables.Such significant sea-ice increases are caused by a cooler ocean surface and stronger sea-ice transports owing to the enhanced heat losses and air-ice stresses induced by the atmospheric variability at 6 h?2 d and 2?8 d,while the effects of the variability at 8 d?1 month are rather weak.The influences of atmospheric variability found here mainly result from wind fluctuations.Our findings in this study indicate the importance of properly resolving high-frequency atmospheric variability in modeling studies.展开更多
Summer precipitation over the Yangtze River basin(YRB)in 2020 experienced a strong subseasonal and synoptic fluctuation in addition to contributing to an exceptionally large seasonal mean precipitation.The cause of th...Summer precipitation over the Yangtze River basin(YRB)in 2020 experienced a strong subseasonal and synoptic fluctuation in addition to contributing to an exceptionally large seasonal mean precipitation.The cause of this higher-frequency fluctuation is examined based on observational analyses.Apart from the continuous northward movement of the climatological mei-yu rainband,the mei-yu rainbelt in the summer of 2020 experienced multiple northward and southward swings.The cause of the swings was attributed to the subseasonal variability of southerly winds to the south and northeasterly winds to the north of the YRB.In addition,synoptic-scale variability,characterized by the eastward propagation of low-level cyclonic vorticity and precipitation anomalies,was also commonplace in the summer of 2020.While the strengthening of both the subseasonal and synoptic variabilities in the summer of 2020 was attributed to the increase of the background mean moisture,the synoptic variability was greatly affected by the subseasonal rainfall variability.As a result,both the synoptic-scale and subseasonal variabilities contributed to the north-south swings of the rainbelt.The large-scale modulations by both the seasonal mean and subseasonal anomalies provide insight regarding the optimization of issuing accurate,extended-range forecasts of extreme weather events.展开更多
In this article,we address both recent advances and open questions in some mathematical and computational issues in geophysical fluid dynamics(GFD)and climate dynamics.The main focus is on 1)the primitive equations(PE...In this article,we address both recent advances and open questions in some mathematical and computational issues in geophysical fluid dynamics(GFD)and climate dynamics.The main focus is on 1)the primitive equations(PEs)models and their related mathematical and computational issues,2)climate variability,predictability and successive bifurcation,and 3)a new dynamical systems theory and its applications to GFD and climate dynamics.展开更多
Extreme flood events are becoming more frequent and intense in recent times, owing to climate change and other anthropogenic factors. Nigeria, the case-study for this research experiences recurrent flooding, with the ...Extreme flood events are becoming more frequent and intense in recent times, owing to climate change and other anthropogenic factors. Nigeria, the case-study for this research experiences recurrent flooding, with the most disastrous being the 2012 flood event that resulted in unprecedented damage to infrastructure, displacement of people, socio-economic disruption, and loss of lives. To mitigate and minimize the impact of such floods now and in the future, effective planning is required, underpinned by analytics based on reliable data and information. Such data are seldom available in many developing regions, owing to financial, technical, and organizational drawbacks that result in short-length and inadequate historical data that are prone to uncertainties if directly applied for flood frequency estimation. This study applies regional Flood Frequency Analysis (FFA) to curtail deficiencies in historical data, by agglomerating data from various sites with similar hydro-geomorphological characteristics and is governed by a similar probability distribution, differing only by an “index-flood”;as well as accounting for climate variability effect. Data from 17 gauging stations within the Ogun-Osun River Basin in Western Nigeria were analysed, resulting in the delineation of 3 sub-regions, of which 2 were homogeneous and 1 heterogeneous. The Generalized Logistic distribution was fitted to the annual maximum flood series for the 2 homogeneous regions to estimate flood magnitudes and the probability of occurrence while accounting for climate variability. The influence of climate variability on flood estimates in the region was linked to the Madden-Julian Oscillation (MJO) climate indices and resulted in increased flood magnitude for regional and direct flood frequency estimates varying from 0% - 35% and demonstrate that multi-decadal changes in atmospheric conditions influence both small and large floods. The results reveal the value of considering climate variability for flood frequency analysis, especially when non-展开更多
Low frequency characteristics of tropical Pacific wind stress anomalies in observation and simulations from the CZ simple atmospheric model and COLA R15 AGCM are analyzed.The results show that ENSO event may be a mult...Low frequency characteristics of tropical Pacific wind stress anomalies in observation and simulations from the CZ simple atmospheric model and COLA R15 AGCM are analyzed.The results show that ENSO event may be a multi-scale process,that is,ENSO time scale has the period longer than three years; biennial oscillation and annual variability.Dynamical characteristics are involved in the evolution process of wind stress anomaly with ENSO time scale: 1) the development and eastward movement of a cyclonic anomaly circulation in subtropical northwestern Pacific and weakening of Southern Oscillation result in the eastward propagation of westerly anomaly along the equator,therefore,interactions between flows in subtropics and in tropics play an important role in the evolution of wind stress anomaly with ENSO time scale; 2) easterly and westerly anomalies with ENSO time scale are one kind of propagating wave,which differs from Barnett's (1991).It is interesting that the evolution of observed and simulated wind stress anomalies with biennial time scale bears a strong resemble to that with ENSO time scale although their period is different.Observed annual variability is weak during 1979-1981 and intensified after 1981,especially it reaches to maximum during 1982-1984,and the spatial structure of the first mode is the ENSO-like pattern.展开更多
Diagnosis is undertaken on the origin for the low-frequency component (LFC) of ENSO variability in the context of 1979—1990 OLR and u-wind datasets.Evidence suggests that ① a power spectrum-yielded maximum,significa...Diagnosis is undertaken on the origin for the low-frequency component (LFC) of ENSO variability in the context of 1979—1990 OLR and u-wind datasets.Evidence suggests that ① a power spectrum-yielded maximum,significant statistically,is derived from the OLR monthly anomalies in a 3—5-year period range over the tropical central/western Pacific;②composite analysis of the signals of the monthly anomaly low frequency component (period>3 years) confirms further the dynamic features of the component as documented in Part Ⅰ:③serving as forcing on ENSO,the related monsoon region represents the source area of the component;④the one-point correlation maps of unfiltered OLR monthly anomalies with zonal wind on a lagged,a simultaneous and a leading basis show clearly the close relation between the u wind-associated eastward travelling low-frequency wave and the low-frequency oscillation of low-latitude central/ western Pacific large-scale convection and the east-moving mode is likely to be excited by the oscillation at a 3—5-year period range.It follows that the large-scale convection oscillation shows up as the origin of the eastward waves,i.e.,ENSO LFC.展开更多
Heart rate variability(HRV) analysis is affected by ectopic beats.An efficient method was proposed to deal with the ectopic beats.The method was based on trend correlation of the heart timing signal.Predictor of R-R i...Heart rate variability(HRV) analysis is affected by ectopic beats.An efficient method was proposed to deal with the ectopic beats.The method was based on trend correlation of the heart timing signal.Predictor of R-R interval(RRI) value at ectopic beat time was constructed by the weight calculation and the slope estimation of preceding normal RRI.The type of ectopic beat was detected and replaced by the predictor of RRI.The performance of the simulated signal after ectopic correction was tested by the standard value using power spectrum density(PSD) estimation,whereas the results of clinical data with ectopic beats were compared with the adjacent ectopic-free data.The result showed the frequency indexes after ectopy corrected had less error than other methods with the test of simulated signal and clinical data.It indicated our method could improve the PSD estimation in HRV analysis.The method had advantages of high accuracy and real time properties to recover the sinus node modulation.展开更多
The impacts of low and high-frequency variability from teleconnections between large scale atmospheric processes and local weather as well as emissions changes on concentrations of particulate matter of 2.5 μm or les...The impacts of low and high-frequency variability from teleconnections between large scale atmospheric processes and local weather as well as emissions changes on concentrations of particulate matter of 2.5 μm or less in diameter ([PM2.5]) were examined for the Fairbanks Metropolitan Area (FMA). October to March and May to August mean [PM2.5] were 1.8 and 3.1 μg·m-3 higher for positive than negative annual mean Pacific Decadal Oscillation. Annual mean [PM2.5] were 3.8 μg·m-3 lower for positive than negative Southern Oscillation Index. On 1999-2018 average, [PM2.5] decreased 2.9 μg·m-3·decade-1. On average over October to March, decadal and inter-annual variability caused higher or similar differences in mean observed [PM2.5] and its species than emission-control measures. The 2006 implementation of Tier 2 for new vehicles decreased observed sulfate concentrations the strongest (~4.95 μg·m-3·decade-1) of all occurred emissions changes. On average, observed [PM2.5] showed elevated values at all sites when wind blew from directions of hot springs. The same was found for the sulfate, ammonium and non-metal components of PM2.5. Observations showed that these geothermal waters contain sulfate, ammonia, boric acid and non-metals. Hot springs of such composition are known to emit hydrogen sulfide and ammonia that can serve as precursors for ammonium and sulfate aerosols.展开更多
Background:The pathogenesis of neck pain in the brain,which is the fourth most common cause of disability,remains unclear.Furthermore,little is known about the characteristics of dynamic local functional brain activit...Background:The pathogenesis of neck pain in the brain,which is the fourth most common cause of disability,remains unclear.Furthermore,little is known about the characteristics of dynamic local functional brain activity in cervical pain.Objective:The present study aimed to investigate the changes of local brain activity caused by chronic neck pain and the factors leading to neck pain.Methods:Using the amplitude of low-frequency fluctuations(ALFF)method combined with sliding window approach,we compared local brain activity that was measured by the functional magnetic resonance imaging(fMRI)of 107 patients with chronic neck pain(CNP)with that of 57 healthy control participants.Five pathogenic factors were selected for correlation analysis.Results:The group comparison results of dynamic amplitude of low-frequency fluctuation(dALFF)variability showed that patients with CNP exhibited decreased dALFF variability in the left inferior temporal gyrus,the middle temporal gyrus,the angular gyrus,the inferior parietal marginal angular gyrus,and the middle occipital gyrus.The abnormal dALFF variability of the left inferior temporal gyrus was negatively correlated with the average daily working hours of patients with neck pain.Conclusions:The findings indicated that the brain regions of patients with CNP responsible for audition,vision,memory,and emotion were subjected to temporal variability of abnormal regional brain activity.Moreover,the dALFF variability in the left inferior temporal gyrus might be a risk factor for neck pain.This study revealed the brain dysfunction of patients with CNP from the perspective of dynamic local brain activity,and highlighted the important role of dALFF variability in understanding the neural mechanism of CNP.展开更多
基金The National Natural Science Foundation of China under contract No.42276003the Oceanic Interdisciplinary Program of Shanghai Jiao Tong University under contract No.SL2021MS021.
文摘The southeastern Indian Ocean is characterized by the warm barrier layer(BL)underlying the cool mixed layer water in austral winter.This phenomenon lasts almost half a year and thus provides a unique positive effect on the upper mixed layer heat content through the entrainment processes at the base of the mixed layer,which has not been well evaluated due to the lack of proper method and dataset.Among various traditional threshold methods,here it is shown that the 5 m fixed depth difference can produce a reliable and accurate estimate of the entrainment heat flux(EHF)in this BL region.The comparison between the daily and monthly EHF warming indicates that the account for high-frequency EHF variability almost doubles the warming effect in the BL period,which can compensate for or even surpass the surface heat loss.This increased warming is a result of stronger relative rate of the mixed layer deepening and larger temperature differences between the mixed layer and its immediate below in the daily-resolving data.The interannual EHF shows a moderately increasing trend and similar variabilities to the Southern Annular Mode(SAM),likely because the mixed layer deepening under the positive SAM trend is accompanied by enhanced turbulent entrainment and thus increases the BL warming.
基金the National Natural Science Foundation of China(Grant No.41806216)the China Postdoctoral Science Foundation(Grant Nos.2019 T120379 and 2018M630499)+4 种基金the Fundamental Research Funds for the Central Universities(Grant No.2018B19214)Zhaomin WANG was supported by the National Natural Science Foundation of China(Grant Nos.41941007 and 41876220)Xia LIN was supported by a project of the National Natural Science Foundation of China(Grant No.41906190)the China Postdoctoral Science Foundation(Grant No.2019M661705)the Fundamental Research Funds for the Central Universities(Grant No.2019B19014).
文摘The relative contributions of atmospheric fluctuations on 6 h?2 d,2?8 d,and 8 d?1 month time scales to the changes in the air?sea fluxes,the SO circulation,and Antarctic sea ice are investigated.It was found that the imposed forcing variability on the three time scales creates a significant increase in wind power input,and hence an increase of about 50%,97%,and 5%of eddy kinetic energy relative to the simulation driven by monthly forcing,respectively.Also,SO circulation and the strength of the upper cell of meridional overturning circulation become strengthened.These results indicate more dominant effects of atmospheric variability on the 2?8 d time scale on the SO circulation.Meanwhile,the 6 h?2 d(2?8 d)atmospheric variability causes an increase in the total sea-ice extent,area,and volume,by about 33%,30%,and 19%(17%,20%,and 25%),respectively,relative to those in the experiment forced by monthly atmospheric variables.Such significant sea-ice increases are caused by a cooler ocean surface and stronger sea-ice transports owing to the enhanced heat losses and air-ice stresses induced by the atmospheric variability at 6 h?2 d and 2?8 d,while the effects of the variability at 8 d?1 month are rather weak.The influences of atmospheric variability found here mainly result from wind fluctuations.Our findings in this study indicate the importance of properly resolving high-frequency atmospheric variability in modeling studies.
基金This work was jointly supported by China National Key R&D Program 2018YFA0605604,NSFC grants(Grant No.42088101,41875069),NSF AGS-2006553NOAA NA18OAR4310298.This is SOEST contribution number 11413,IPRC contribution number 1541,and ESMC number 357.
文摘Summer precipitation over the Yangtze River basin(YRB)in 2020 experienced a strong subseasonal and synoptic fluctuation in addition to contributing to an exceptionally large seasonal mean precipitation.The cause of this higher-frequency fluctuation is examined based on observational analyses.Apart from the continuous northward movement of the climatological mei-yu rainband,the mei-yu rainbelt in the summer of 2020 experienced multiple northward and southward swings.The cause of the swings was attributed to the subseasonal variability of southerly winds to the south and northeasterly winds to the north of the YRB.In addition,synoptic-scale variability,characterized by the eastward propagation of low-level cyclonic vorticity and precipitation anomalies,was also commonplace in the summer of 2020.While the strengthening of both the subseasonal and synoptic variabilities in the summer of 2020 was attributed to the increase of the background mean moisture,the synoptic variability was greatly affected by the subseasonal rainfall variability.As a result,both the synoptic-scale and subseasonal variabilities contributed to the north-south swings of the rainbelt.The large-scale modulations by both the seasonal mean and subseasonal anomalies provide insight regarding the optimization of issuing accurate,extended-range forecasts of extreme weather events.
基金the grants from the Office of Naval Research,from the National Science Foundation,and from the National Nature Science Foundation of China(40325013,40675046)。
文摘In this article,we address both recent advances and open questions in some mathematical and computational issues in geophysical fluid dynamics(GFD)and climate dynamics.The main focus is on 1)the primitive equations(PEs)models and their related mathematical and computational issues,2)climate variability,predictability and successive bifurcation,and 3)a new dynamical systems theory and its applications to GFD and climate dynamics.
文摘Extreme flood events are becoming more frequent and intense in recent times, owing to climate change and other anthropogenic factors. Nigeria, the case-study for this research experiences recurrent flooding, with the most disastrous being the 2012 flood event that resulted in unprecedented damage to infrastructure, displacement of people, socio-economic disruption, and loss of lives. To mitigate and minimize the impact of such floods now and in the future, effective planning is required, underpinned by analytics based on reliable data and information. Such data are seldom available in many developing regions, owing to financial, technical, and organizational drawbacks that result in short-length and inadequate historical data that are prone to uncertainties if directly applied for flood frequency estimation. This study applies regional Flood Frequency Analysis (FFA) to curtail deficiencies in historical data, by agglomerating data from various sites with similar hydro-geomorphological characteristics and is governed by a similar probability distribution, differing only by an “index-flood”;as well as accounting for climate variability effect. Data from 17 gauging stations within the Ogun-Osun River Basin in Western Nigeria were analysed, resulting in the delineation of 3 sub-regions, of which 2 were homogeneous and 1 heterogeneous. The Generalized Logistic distribution was fitted to the annual maximum flood series for the 2 homogeneous regions to estimate flood magnitudes and the probability of occurrence while accounting for climate variability. The influence of climate variability on flood estimates in the region was linked to the Madden-Julian Oscillation (MJO) climate indices and resulted in increased flood magnitude for regional and direct flood frequency estimates varying from 0% - 35% and demonstrate that multi-decadal changes in atmospheric conditions influence both small and large floods. The results reveal the value of considering climate variability for flood frequency analysis, especially when non-
文摘Low frequency characteristics of tropical Pacific wind stress anomalies in observation and simulations from the CZ simple atmospheric model and COLA R15 AGCM are analyzed.The results show that ENSO event may be a multi-scale process,that is,ENSO time scale has the period longer than three years; biennial oscillation and annual variability.Dynamical characteristics are involved in the evolution process of wind stress anomaly with ENSO time scale: 1) the development and eastward movement of a cyclonic anomaly circulation in subtropical northwestern Pacific and weakening of Southern Oscillation result in the eastward propagation of westerly anomaly along the equator,therefore,interactions between flows in subtropics and in tropics play an important role in the evolution of wind stress anomaly with ENSO time scale; 2) easterly and westerly anomalies with ENSO time scale are one kind of propagating wave,which differs from Barnett's (1991).It is interesting that the evolution of observed and simulated wind stress anomalies with biennial time scale bears a strong resemble to that with ENSO time scale although their period is different.Observed annual variability is weak during 1979-1981 and intensified after 1981,especially it reaches to maximum during 1982-1984,and the spatial structure of the first mode is the ENSO-like pattern.
文摘Diagnosis is undertaken on the origin for the low-frequency component (LFC) of ENSO variability in the context of 1979—1990 OLR and u-wind datasets.Evidence suggests that ① a power spectrum-yielded maximum,significant statistically,is derived from the OLR monthly anomalies in a 3—5-year period range over the tropical central/western Pacific;②composite analysis of the signals of the monthly anomaly low frequency component (period>3 years) confirms further the dynamic features of the component as documented in Part Ⅰ:③serving as forcing on ENSO,the related monsoon region represents the source area of the component;④the one-point correlation maps of unfiltered OLR monthly anomalies with zonal wind on a lagged,a simultaneous and a leading basis show clearly the close relation between the u wind-associated eastward travelling low-frequency wave and the low-frequency oscillation of low-latitude central/ western Pacific large-scale convection and the east-moving mode is likely to be excited by the oscillation at a 3—5-year period range.It follows that the large-scale convection oscillation shows up as the origin of the eastward waves,i.e.,ENSO LFC.
基金Project supported by the Key Industrial Projects of Science of Zhejiang Province (No. 2007C21079)the National Key Technologies R&D Program (No. 2007BAI07A28) of China
文摘Heart rate variability(HRV) analysis is affected by ectopic beats.An efficient method was proposed to deal with the ectopic beats.The method was based on trend correlation of the heart timing signal.Predictor of R-R interval(RRI) value at ectopic beat time was constructed by the weight calculation and the slope estimation of preceding normal RRI.The type of ectopic beat was detected and replaced by the predictor of RRI.The performance of the simulated signal after ectopic correction was tested by the standard value using power spectrum density(PSD) estimation,whereas the results of clinical data with ectopic beats were compared with the adjacent ectopic-free data.The result showed the frequency indexes after ectopy corrected had less error than other methods with the test of simulated signal and clinical data.It indicated our method could improve the PSD estimation in HRV analysis.The method had advantages of high accuracy and real time properties to recover the sinus node modulation.
文摘The impacts of low and high-frequency variability from teleconnections between large scale atmospheric processes and local weather as well as emissions changes on concentrations of particulate matter of 2.5 μm or less in diameter ([PM2.5]) were examined for the Fairbanks Metropolitan Area (FMA). October to March and May to August mean [PM2.5] were 1.8 and 3.1 μg·m-3 higher for positive than negative annual mean Pacific Decadal Oscillation. Annual mean [PM2.5] were 3.8 μg·m-3 lower for positive than negative Southern Oscillation Index. On 1999-2018 average, [PM2.5] decreased 2.9 μg·m-3·decade-1. On average over October to March, decadal and inter-annual variability caused higher or similar differences in mean observed [PM2.5] and its species than emission-control measures. The 2006 implementation of Tier 2 for new vehicles decreased observed sulfate concentrations the strongest (~4.95 μg·m-3·decade-1) of all occurred emissions changes. On average, observed [PM2.5] showed elevated values at all sites when wind blew from directions of hot springs. The same was found for the sulfate, ammonium and non-metal components of PM2.5. Observations showed that these geothermal waters contain sulfate, ammonia, boric acid and non-metals. Hot springs of such composition are known to emit hydrogen sulfide and ammonia that can serve as precursors for ammonium and sulfate aerosols.
基金supported by the Science and Technology Support Program of Sichuan Province(2018JY0562)the National Natural Science Foundation of China(81722050,81973962 and U1808204)the Key Project of Research and Development of Ministry of Science and Technology(2018AAA0100705).
文摘Background:The pathogenesis of neck pain in the brain,which is the fourth most common cause of disability,remains unclear.Furthermore,little is known about the characteristics of dynamic local functional brain activity in cervical pain.Objective:The present study aimed to investigate the changes of local brain activity caused by chronic neck pain and the factors leading to neck pain.Methods:Using the amplitude of low-frequency fluctuations(ALFF)method combined with sliding window approach,we compared local brain activity that was measured by the functional magnetic resonance imaging(fMRI)of 107 patients with chronic neck pain(CNP)with that of 57 healthy control participants.Five pathogenic factors were selected for correlation analysis.Results:The group comparison results of dynamic amplitude of low-frequency fluctuation(dALFF)variability showed that patients with CNP exhibited decreased dALFF variability in the left inferior temporal gyrus,the middle temporal gyrus,the angular gyrus,the inferior parietal marginal angular gyrus,and the middle occipital gyrus.The abnormal dALFF variability of the left inferior temporal gyrus was negatively correlated with the average daily working hours of patients with neck pain.Conclusions:The findings indicated that the brain regions of patients with CNP responsible for audition,vision,memory,and emotion were subjected to temporal variability of abnormal regional brain activity.Moreover,the dALFF variability in the left inferior temporal gyrus might be a risk factor for neck pain.This study revealed the brain dysfunction of patients with CNP from the perspective of dynamic local brain activity,and highlighted the important role of dALFF variability in understanding the neural mechanism of CNP.
