Extended Impact of Cold Air Invasions in East Asia in Response to a Warm South China Sea and Philippine Sea

During boreal winter, the invasion of cold air can lead to remarkable temperature drops in East Asia which can result in serious socioeconomic impacts. Here, we find that the intensity of strong synoptic cold days in the East China Sea and Indochina Peninsula are increasing. The enhanced synoptic cold days in these two regions are attributed to surface warming over the South China Sea and Philippine Sea(SCSPS). The oceanic forcing of the SCSPS on the synoptic cold days in the two regions is veri...     

多尺度空间单元区域划分方法

传统空间单元的区域划分通常仅以属性数据作为划分依据，而对单元之间空间依赖关系考虑不周。在尺度空间理论基础上，提出多尺度空间单元区域划分方法，在考虑空间单元属性信息的同时，增加了空间单元的相互依赖关系，使得在空间尺度在由小变大过程中，具有高度空间相互依赖关系的空间单元相互融合，得到不同空间尺度下的区域划分。以江苏省从1978年到1995年的18年社会经济发展数据为基础，进行了全省社会经济发展水平的区域划分的试验，结果表明与实际发展水平的分布情况相吻合。     

An elliptical basis function network for classification of remote sensing images

An elliptical basis function (EBF) network is employed in this study for the classification of remotely sensed images. Though similar in structure, the EBF network differs from the well-known radial basis function (RBF) network by incorporating full covariance matrices and employing the expectation-maximization (EM) algorithm to estimate the basis functions. Since remotely sensed data often take on mixture-density distributions in the feature space, the network not only possesses the advantage of the RBF mechanism, but also utilizes the EM algorithm to compute the maximum likelihood estimates of the mean vectors and covariance matrices of a Gaussian mixture distribution in the training phase. Experimental results show that the EM-based EBF network is more effective in training and simpler in structure than an RBF network constructed for the same task.The research was supported by grant 40101021 from the Natural Science Foundation of China, and grant 2002AA135230 from Hi-Tech research and development program of China. The authors would like to thank the reviewers for their valuable comments.     

The force-restore method revisited

The so-called ‘force-restore method’ has been used with considerable success in numerical weather prediction models to simulate diurnal variations of ground temperature. This note demonstrates that the force-restore equation is no more nor less than an approximation to the surface-energy-balance equation. The applicability of the method to the case of multi-component heating functions and to the case in which the soil is covered by a litter layer is discussed.     

Temporal changes of polyphenols and enzyme activities in seedlings of Kandelia obovata under lead and manganese stresses

The temporal responses of peroxidase (POD), superoxide dismutase (SOD), total polyphenols (TP), extractable condensed tannins (ECT) to different levels of lead (Pb) or manganese (Mn) stress, as well as the metal accumulation, in seedlings of Kandelia obovata were investigated. Both stress time and stress intensity had significant effects with significant accumulation of Pb and Mn in roots at Day 1. Pb and Mn showed no significant effects on root or leaf TP and ECT at Day 1. Prolonged exposure to metals caused significant drops of root TP and ECT but increased in leaves at Days 7 and 49. POD activities decreased in both roots and leaves at Day 1, while POD and SOD both increased under moderate levels of Pb and Mn at Day 7. The present study showed that antioxidative enzyme activities were more sensitive indicators to Pb or Mn stresses than phenolic compounds.     

Theory for Reconstruction of an Unknown Number of Contaminant Sources using Probabilistic Inference

We address the inverse problem of source reconstruction for the difficult case of multiple sources when the number of sources is unknown a priori. The problem is solved using a Bayesian probabilistic inferential framework in which Bayesian probability theory is used to derive the posterior probability density function for the number of sources and for the parameters (e.g., location, emission rate, release time and duration) that characterize each source. A mapping (source–receptor relationship) that relates a multiple source distribution to the concentration measurements made by an array of detectors is formulated based on a forward-time Lagrangian stochastic model. A computationally efficient methodology for determination of the likelihood function for the problem, based on an adjoint representation of the source–receptor relationship and realized in terms of a backward-time Lagrangian stochastic model, is described. An efficient computational algorithm based on a parallel tempered Metropolis-coupled reversible-jump Markov chain Monte Carlo (MCMC) method is formulated and implemented to draw samples from the posterior probability density function of the source parameters. This methodology allows the MCMC method to initiate jumps between the hypothesis spaces corresponding to different numbers of sources in the source distribution and, thereby, allows a sample from the full joint posterior distribution of the number of sources and the parameters for each source to be obtained. The proposed methodology for source reconstruction is tested using synthetic concentration data generated for cases involving two and three unknown sources.     

Recurrence statistics of concentration fluctuations in plumes within a near-neutral atmospheric surface layer

This study examines the statistical properties of the concentration derivative, , for a dispersing plume in a near-neutrally stratified atmospheric surface layer. Towards this goal, the probability density function (pdf) of , and the conditional pdf of given a fixed concentration level, , have been measured. These pdfs are found to be modeled well by a generalizedq-Gaussian (gqG) distribution with intermittency exponent,q, equal to 0.3 and 3/4, respectively. These results highlight the strong intermittency effect (patchiness) of the small-scale concentration eddy structures in the plume. The distribution of time intervals between successive high peaks in the squared derivative process, x², is found to be well approximated by a power-law distribution, implying that occurrences of these high peaks are much more clustered than would be predicted by a Poisson or shot-noise process. The results are used to improve models for the joint pdf of and , and for the expected number of upcrossings per unit time interval of a fixed concentration level that have been proposed by Kristensenet al. (1989). The predictions of the improved models are in accord with observations, and suggest that the intercorrelation between and must be explicitly incorporated if good estimates of the upcrossing intensity are to be obtained.