In this paper,a statistical method called Generalized Equilibrium Feedback Analysis(GEFA)is used to investigate the responses of the North Pacific Storm Track(NPST)in the cold season to the multi-scale oceanic variati...In this paper,a statistical method called Generalized Equilibrium Feedback Analysis(GEFA)is used to investigate the responses of the North Pacific Storm Track(NPST)in the cold season to the multi-scale oceanic variations of the Kuroshio Extension(KE)system,including its large-scale variation,oceanic front meridional shift,and mesoscale eddy activity.Results show that in the cold season from the lower to the upper troposphere,the KE large-scale variation significantly weakens the storm track activity over the central North Pacific south of 30°N.The northward shift of the KE front significantly strengthens the storm track activity over the western and central North Pacific south of 40°N,resulting in a southward shift of the NPST.In contrast,the NPST response to KE mesoscale eddy activity is not so significant and relatively shallow,which only shows some significant positive signals near the dateline in the lower and middle troposphere.Furthermore,it is found that baroclinicity and baroclinic energy conversion play an important role in the formation of the NPST response to the KE multi-scale oceanic variations.展开更多
To effectively extract multi-scale information from observation data and improve computational efficiency,a multi-scale second-order autoregressive recursive filter(MSRF)method is designed.The second-order autoregress...To effectively extract multi-scale information from observation data and improve computational efficiency,a multi-scale second-order autoregressive recursive filter(MSRF)method is designed.The second-order autoregressive filter used in this study has been attempted to replace the traditional first-order recursive filter used in spatial multi-scale recursive filter(SMRF)method.The experimental results indicate that the MSRF scheme successfully extracts various scale information resolved by observations.Moreover,compared with the SMRF scheme,the MSRF scheme improves computational accuracy and efficiency to some extent.The MSRF scheme can not only propagate to a longer distance without the attenuation of innovation,but also reduce the mean absolute deviation between the reconstructed sea ice concentration results and observations reduced by about 3.2%compared to the SMRF scheme.On the other hand,compared with traditional first-order recursive filters using in the SMRF scheme that multiple filters are executed,the MSRF scheme only needs to perform two filter processes in one iteration,greatly improving filtering efficiency.In the two-dimensional experiment of sea ice concentration,the calculation time of the MSRF scheme is only 1/7 of that of SMRF scheme.This means that the MSRF scheme can achieve better performance with less computational cost,which is of great significance for further application in real-time ocean or sea ice data assimilation systems in the future.展开更多
Both of the climate changes in arid Central Asia (ACA) and arid region of Northwest China (Fig. 1) were dominated by the mid-latitude westerlies (Chen et al., 2009). Chen et al. (2008)synthesized a set of high resolut...Both of the climate changes in arid Central Asia (ACA) and arid region of Northwest China (Fig. 1) were dominated by the mid-latitude westerlies (Chen et al., 2009). Chen et al. (2008)synthesized a set of high resolution lake sediment records from ACA and demonstrated that the nature of Holocene climatic and environmental evolution in both of the arid regions of Northwest China and the whole ACA differs from that of mid-latitude monsoon dominated Asia. In fact, many studies have demonstrated the occurrence of different patterns of precipitation and/or moisture variations between westerlydominated Asia and monsoon-dominated Asia on decadal (Ma and Fu, 2006; Jiang et al., 2009; Chen et al., 2011; Huang et al., 2013) to multi-millennial time scales (Chen et al., 2010; Zhou et al., 2011). Therefore, Chen et al. (2009) have展开更多
On the basis of the absolute and relative gravity observations in North China,spatial dynamic variation of regional gravity fields is obtained. A multi-scale decomposition technique is used to separate anomalies at di...On the basis of the absolute and relative gravity observations in North China,spatial dynamic variation of regional gravity fields is obtained. A multi-scale decomposition technique is used to separate anomalies at different depths,and give some explanation to gravity variation at different time space scales. Gravity variation trends in North China are improved. Based on this result and the analysis of wavelet power spectrum,the images of the depth of wavelet approximation and detail are obtained. The results obtained are of scientific significance for the deep understanding of potential seismic risk in North China from gravity variations in different time space scales.展开更多
The sea ice concentration observation from satellite remote sensing includes the spatial multi-scale information.However,traditional data assimilation methods cannot better extract the valuable information due to the ...The sea ice concentration observation from satellite remote sensing includes the spatial multi-scale information.However,traditional data assimilation methods cannot better extract the valuable information due to the complicated variability of the sea ice concentration in the marginal ice zone.A successive corrections analysis using variational optimization method,called spatial multi-scale recursive filter(SMRF),has been designed in this paper to extract multi-scale information resolved by sea ice observations.It is a combination of successive correction methods(SCM)and minimization algorithms,in which various observational scales,from longer to shorter wavelengths,can be extracted successively.As a variational objective analysis scheme,it gains the advantage over the conventional approaches that analyze all scales resolved by observations at one time,and also,the specification of parameters is more convenient.Results of single-observation experiment demonstrate that the SMRF scheme possesses a good ability in propagating observational signals.Further,it shows a superior performance in extracting multi-scale information in a two-dimensional sea ice concentration(SIC)experiment with the real observations from Special Sensor Microwave/Imager SIC(SSMI).展开更多
The onset of the South China Sea summer monsoon(SCSSM) heralds the establishment of the large-scale East Asian summer monsoon and the western North Pacific summer monsoon, as well as the beginning of the major rainy s...The onset of the South China Sea summer monsoon(SCSSM) heralds the establishment of the large-scale East Asian summer monsoon and the western North Pacific summer monsoon, as well as the beginning of the major rainy season. The occurrence of an early or late SCSSM onset is an important indicator for the summertime climate anomalies over East and Southeast Asia. Therefore, the onset of the SCSSM has received extensive research attention, and has been one of the key foci of monsoon research in recent decades. This paper reviews the multi-scale climate variations(from interdecadal to synoptic scales)and mechanisms of the SCSSM onset, with special attention paid to the progress in the past five years. On the interdecadal timescale, the SCSSM onset underwent a significant advancement in the mid-to-late 1990s, which may have been related to the background condition of the Pacific Ocean. On the interannual timescale, El Ni?o-Southern Oscillation(ENSO) is considered to be the most critical factor controlling the variability of the SCSSM onset. However, the linkage between ENSO and the SCSSM onset has become much weaker and insignificant in recent years. The intraseasonal oscillations(including the 30–60-day oscillation and quasi-biweekly oscillation) are important modulators of the SCSSM onset. The transition from an inactive phase to an active phase may be more worthy of attention than the phase itself. There appear to be close interactions between the SCSSM onset and synoptic-scale systems like tropical cyclones(TCs). TCs are important triggers for the SCSSM onset, while in return the SCSSM onset provides a favorable background condition for the formation and development of TCs. In addition, this paper also reviews a series of recent works on the withdrawal of the SCSSM. Finally, to close the paper, some important scientific issues worthy of further investigation are put forward.展开更多
The Medieval Climate Anomaly(MCA,AD950-1250)is the most recent warm period lasting for several hundred years and is regarded as a reference scenario when studying the impact of and adaptation to global and regional wa...The Medieval Climate Anomaly(MCA,AD950-1250)is the most recent warm period lasting for several hundred years and is regarded as a reference scenario when studying the impact of and adaptation to global and regional warming.In this study,we investigated the characteristics of temperature variations on decadal-centennial scales during the MCA for four regions(Northeast,Northwest,Central-east,and Tibetan Plateau)in China,based on high-resolution temperature reconstructions and related warm-cold records from historical documents.The ensemble empirical mode decomposition method is used to analyze the time series.The results showed that for China as a whole,the longest warm period during the last 2000 years occurred in the 10th-13th centuries,although there were multi-decadal cold intervals in the middle to late 12th century.However,in the beginning and ending decades,warm peaks and phases on the decadal scale of the MCA for different regions were not consistent with each other.On the inter-decadal scale,regional temperature variations were similar from 950 to 1130;moreover,their amplitudes became smaller,and the phases did not agree well from 1130 to 1250.On the multi-decadal to centennial scale,all four regions began to warm in the early 10th century and experienced two cold intervals during the MCA.However,the Northwest and Central-east China were in step with each other while the warm periods in the Northeast China and Tibetan Plateau ended about 40-50 years earlier.On the multi-centennial scale,the mean temperature difference between the MCA and Little Ice Age was significant in Northeast and Central-east China but not in the Northwest China and Tibetan Plateau.Compared to the mean temperature of the 20th century,a comparable warmth in the MCA was found in the Central-east China,but there was a little cooling in Northeast China;meanwhile,there were significantly lower temperatures in Northwest China and Tibetan Plateau.展开更多
This paper proposes a new cooperative projection neural network （CPNN）, which combines automatically three individual neural network models with a common projection term. As a special case, the proposed CPNN can inc...This paper proposes a new cooperative projection neural network （CPNN）, which combines automatically three individual neural network models with a common projection term. As a special case, the proposed CPNN can include three recent recurrent neural networks for solving monotone variational inequality problems with limit or linear constraints, respectively. Under the monotonicity condition of the corresponding Lagrangian mapping, the proposed CPNN is theoretically guaranteed to solve monotone variational inequality problems and a class of nonmonotone variational inequality problems with linear and nonlinear constraints. Unlike the extended projection neural network, the proposed CPNN has no limitation on the initial point for global convergence. Compared with other related cooperative neural networks and numerical optimization algorithms, the proposed CPNN has a low computational complexity and requires weak convergence conditions. An application in real-time grasping force optimization and examples demonstrate good performance of the proposed CPNN.展开更多
针对基于消息传递算法的节点定位方法复杂度和通信开销较高的问题,提出一种适用于节点可移动网络的低复杂度低协作开销的节点自定位算法。为降低通信负载,该算法将消息约束为高斯型函数,网络中只需传输各消息的均值和方差,并采用适用于...针对基于消息传递算法的节点定位方法复杂度和通信开销较高的问题,提出一种适用于节点可移动网络的低复杂度低协作开销的节点自定位算法。为降低通信负载,该算法将消息约束为高斯型函数,网络中只需传输各消息的均值和方差,并采用适用于指数模型的变分消息传递(VMP)算法以降低计算复杂度。首先,根据节点的历史轨迹对节点位置进行预测,得到当前时刻的先验信息。然后,在因子图上按照VMP消息更新规则、通过迭代近似求解节点位置变量的后验分布。在消息更新中,对于非线性测距模型引起的非高斯置信,通过非线性项的二阶泰勒级数展开将其近似为高斯型函数。最后,根据最大后验估计准则得到位置估计。仿真结果表明,该算法的定位精度与基于非参数化置信传播的SPAWN(Sum-Product Algorithm over a Wireless Network)接近,但计算复杂度和通信负载均显著降低。展开更多
基金jointly supported by the National Natural Science Foundation of China (Grant Nos. 42105066, 42088101, 41975066)supported by the China Postdoctoral Science Foundation (2021M701754)+1 种基金the Postdoctoral Research Funding of Jiangsu Province (2021K052A)the Research Project of the National University of Defense Technology (ZK20-45)
文摘In this paper,a statistical method called Generalized Equilibrium Feedback Analysis(GEFA)is used to investigate the responses of the North Pacific Storm Track(NPST)in the cold season to the multi-scale oceanic variations of the Kuroshio Extension(KE)system,including its large-scale variation,oceanic front meridional shift,and mesoscale eddy activity.Results show that in the cold season from the lower to the upper troposphere,the KE large-scale variation significantly weakens the storm track activity over the central North Pacific south of 30°N.The northward shift of the KE front significantly strengthens the storm track activity over the western and central North Pacific south of 40°N,resulting in a southward shift of the NPST.In contrast,the NPST response to KE mesoscale eddy activity is not so significant and relatively shallow,which only shows some significant positive signals near the dateline in the lower and middle troposphere.Furthermore,it is found that baroclinicity and baroclinic energy conversion play an important role in the formation of the NPST response to the KE multi-scale oceanic variations.
基金The National Key Research and Development Program of China under contract No.2023YFC3107701the National Natural Science Foundation of China under contract No.42375143.
文摘To effectively extract multi-scale information from observation data and improve computational efficiency,a multi-scale second-order autoregressive recursive filter(MSRF)method is designed.The second-order autoregressive filter used in this study has been attempted to replace the traditional first-order recursive filter used in spatial multi-scale recursive filter(SMRF)method.The experimental results indicate that the MSRF scheme successfully extracts various scale information resolved by observations.Moreover,compared with the SMRF scheme,the MSRF scheme improves computational accuracy and efficiency to some extent.The MSRF scheme can not only propagate to a longer distance without the attenuation of innovation,but also reduce the mean absolute deviation between the reconstructed sea ice concentration results and observations reduced by about 3.2%compared to the SMRF scheme.On the other hand,compared with traditional first-order recursive filters using in the SMRF scheme that multiple filters are executed,the MSRF scheme only needs to perform two filter processes in one iteration,greatly improving filtering efficiency.In the two-dimensional experiment of sea ice concentration,the calculation time of the MSRF scheme is only 1/7 of that of SMRF scheme.This means that the MSRF scheme can achieve better performance with less computational cost,which is of great significance for further application in real-time ocean or sea ice data assimilation systems in the future.
文摘Both of the climate changes in arid Central Asia (ACA) and arid region of Northwest China (Fig. 1) were dominated by the mid-latitude westerlies (Chen et al., 2009). Chen et al. (2008)synthesized a set of high resolution lake sediment records from ACA and demonstrated that the nature of Holocene climatic and environmental evolution in both of the arid regions of Northwest China and the whole ACA differs from that of mid-latitude monsoon dominated Asia. In fact, many studies have demonstrated the occurrence of different patterns of precipitation and/or moisture variations between westerlydominated Asia and monsoon-dominated Asia on decadal (Ma and Fu, 2006; Jiang et al., 2009; Chen et al., 2011; Huang et al., 2013) to multi-millennial time scales (Chen et al., 2010; Zhou et al., 2011). Therefore, Chen et al. (2009) have
基金funded by the Special Fund for Earthquake Scientific Research of China(201308004,201308009)
文摘On the basis of the absolute and relative gravity observations in North China,spatial dynamic variation of regional gravity fields is obtained. A multi-scale decomposition technique is used to separate anomalies at different depths,and give some explanation to gravity variation at different time space scales. Gravity variation trends in North China are improved. Based on this result and the analysis of wavelet power spectrum,the images of the depth of wavelet approximation and detail are obtained. The results obtained are of scientific significance for the deep understanding of potential seismic risk in North China from gravity variations in different time space scales.
基金The National Key Research and Development Program of China under contract Nos 2017YFC1404103 and 2016YFC1401701the National Programme on Global Change and Air-Sea Interaction of China under contract GASI-IPOVAI-04the National Natural Science Foundation of China under contract Nos 41876014 and 41606039.
文摘The sea ice concentration observation from satellite remote sensing includes the spatial multi-scale information.However,traditional data assimilation methods cannot better extract the valuable information due to the complicated variability of the sea ice concentration in the marginal ice zone.A successive corrections analysis using variational optimization method,called spatial multi-scale recursive filter(SMRF),has been designed in this paper to extract multi-scale information resolved by sea ice observations.It is a combination of successive correction methods(SCM)and minimization algorithms,in which various observational scales,from longer to shorter wavelengths,can be extracted successively.As a variational objective analysis scheme,it gains the advantage over the conventional approaches that analyze all scales resolved by observations at one time,and also,the specification of parameters is more convenient.Results of single-observation experiment demonstrate that the SMRF scheme possesses a good ability in propagating observational signals.Further,it shows a superior performance in extracting multi-scale information in a two-dimensional sea ice concentration(SIC)experiment with the real observations from Special Sensor Microwave/Imager SIC(SSMI).
基金supported by the National Natural Science Foundation of China (Grant No. 41721004)。
文摘The onset of the South China Sea summer monsoon(SCSSM) heralds the establishment of the large-scale East Asian summer monsoon and the western North Pacific summer monsoon, as well as the beginning of the major rainy season. The occurrence of an early or late SCSSM onset is an important indicator for the summertime climate anomalies over East and Southeast Asia. Therefore, the onset of the SCSSM has received extensive research attention, and has been one of the key foci of monsoon research in recent decades. This paper reviews the multi-scale climate variations(from interdecadal to synoptic scales)and mechanisms of the SCSSM onset, with special attention paid to the progress in the past five years. On the interdecadal timescale, the SCSSM onset underwent a significant advancement in the mid-to-late 1990s, which may have been related to the background condition of the Pacific Ocean. On the interannual timescale, El Ni?o-Southern Oscillation(ENSO) is considered to be the most critical factor controlling the variability of the SCSSM onset. However, the linkage between ENSO and the SCSSM onset has become much weaker and insignificant in recent years. The intraseasonal oscillations(including the 30–60-day oscillation and quasi-biweekly oscillation) are important modulators of the SCSSM onset. The transition from an inactive phase to an active phase may be more worthy of attention than the phase itself. There appear to be close interactions between the SCSSM onset and synoptic-scale systems like tropical cyclones(TCs). TCs are important triggers for the SCSSM onset, while in return the SCSSM onset provides a favorable background condition for the formation and development of TCs. In addition, this paper also reviews a series of recent works on the withdrawal of the SCSSM. Finally, to close the paper, some important scientific issues worthy of further investigation are put forward.
基金National Key R&D Program of China,No.2017YFA0603300National Natural Science Foundation of China,No.41671036,No.41831174The Strategic Priority Research Program of the Chinese Academy of Sciences,No.XDA 19040101。
文摘The Medieval Climate Anomaly(MCA,AD950-1250)is the most recent warm period lasting for several hundred years and is regarded as a reference scenario when studying the impact of and adaptation to global and regional warming.In this study,we investigated the characteristics of temperature variations on decadal-centennial scales during the MCA for four regions(Northeast,Northwest,Central-east,and Tibetan Plateau)in China,based on high-resolution temperature reconstructions and related warm-cold records from historical documents.The ensemble empirical mode decomposition method is used to analyze the time series.The results showed that for China as a whole,the longest warm period during the last 2000 years occurred in the 10th-13th centuries,although there were multi-decadal cold intervals in the middle to late 12th century.However,in the beginning and ending decades,warm peaks and phases on the decadal scale of the MCA for different regions were not consistent with each other.On the inter-decadal scale,regional temperature variations were similar from 950 to 1130;moreover,their amplitudes became smaller,and the phases did not agree well from 1130 to 1250.On the multi-decadal to centennial scale,all four regions began to warm in the early 10th century and experienced two cold intervals during the MCA.However,the Northwest and Central-east China were in step with each other while the warm periods in the Northeast China and Tibetan Plateau ended about 40-50 years earlier.On the multi-centennial scale,the mean temperature difference between the MCA and Little Ice Age was significant in Northeast and Central-east China but not in the Northwest China and Tibetan Plateau.Compared to the mean temperature of the 20th century,a comparable warmth in the MCA was found in the Central-east China,but there was a little cooling in Northeast China;meanwhile,there were significantly lower temperatures in Northwest China and Tibetan Plateau.
基金Supported by the National Natural Science Foundation of China (Grant No. 60875085)the Natural Science Foundation of Fujian Province(Grant No. 2008J0019)
文摘This paper proposes a new cooperative projection neural network （CPNN）, which combines automatically three individual neural network models with a common projection term. As a special case, the proposed CPNN can include three recent recurrent neural networks for solving monotone variational inequality problems with limit or linear constraints, respectively. Under the monotonicity condition of the corresponding Lagrangian mapping, the proposed CPNN is theoretically guaranteed to solve monotone variational inequality problems and a class of nonmonotone variational inequality problems with linear and nonlinear constraints. Unlike the extended projection neural network, the proposed CPNN has no limitation on the initial point for global convergence. Compared with other related cooperative neural networks and numerical optimization algorithms, the proposed CPNN has a low computational complexity and requires weak convergence conditions. An application in real-time grasping force optimization and examples demonstrate good performance of the proposed CPNN.
文摘针对基于消息传递算法的节点定位方法复杂度和通信开销较高的问题,提出一种适用于节点可移动网络的低复杂度低协作开销的节点自定位算法。为降低通信负载,该算法将消息约束为高斯型函数,网络中只需传输各消息的均值和方差,并采用适用于指数模型的变分消息传递(VMP)算法以降低计算复杂度。首先,根据节点的历史轨迹对节点位置进行预测,得到当前时刻的先验信息。然后,在因子图上按照VMP消息更新规则、通过迭代近似求解节点位置变量的后验分布。在消息更新中,对于非线性测距模型引起的非高斯置信,通过非线性项的二阶泰勒级数展开将其近似为高斯型函数。最后,根据最大后验估计准则得到位置估计。仿真结果表明,该算法的定位精度与基于非参数化置信传播的SPAWN(Sum-Product Algorithm over a Wireless Network)接近,但计算复杂度和通信负载均显著降低。
