Showing papers by "Nanjing University of Information Science and Technology published in 2011"

Long-term impacts of aerosols on the vertical development of clouds and precipitation

Abstract: Aerosols alter cloud density and the radiative balance of the atmosphere. This leads to changes in cloud microphysics and atmospheric stability, which can either suppress or foster the development of clouds and precipitation. The net effect is largely unknown, but depends on meteorological conditions and aerosol properties. Here, we examine the long-term impact of aerosols on the vertical development of clouds and rainfall frequencies, using a 10-year dataset of aerosol, cloud and meteorological variables collected in the Southern Great Plains in the United States. We show that cloud-top height and thickness increase with aerosol concentration measured near the ground in mixed-phase clouds—which contain both liquid water and ice—that have a warm, low base. We attribute the effect, which is most significant in summer, to an aerosol-induced invigoration of upward winds. In contrast, we find no change in cloud-top height and precipitation with aerosol concentration in clouds with no ice or cool bases. We further show that precipitation frequency and rain rate are altered by aerosols. Rain increases with aerosol concentration in deep clouds that have a high liquid-water content, but declines in clouds that have a low liquid-water content. Simulations using a cloud-resolving model confirm these observations. Our findings provide unprecedented insights of the long-term net impacts of aerosols on clouds and precipitation.

East Asian Studies of Tropospheric Aerosols and their Impact on Regional Climate (EAST‐AIRC): An overview

Abstract: As the most populated region of the world, Asia is a major source of aerosols with potential large impact over vast downstream areas, Papers published in this special section describe the variety of aerosols observed in China and their effects and interactions with the regional climate as part of the East Asian Study of Tropospheric Aerosols and their Impact on Regional Climate (EAST-AIRC), The majority of the papers are based on analyses of observations made under three field projects, namely, the Atmospheric Radiation Measurements (ARM) Mobile Facility mission in China (AMF-China), the East Asian Study of Tropospheric Aerosols: An International Regional Experiment (EAST-AIRE), and the Atmospheric Aerosols of China and their Climate Effects (AACCE), The former two are U,S,-China collaborative projects, and the latter is a part of the China's National Basic Research program (or often referred to as "973 project"), Routine meteorological data of China are also employed in some studies, The wealth of general and speCIalized measurements lead to extensive and close-up investigations of the optical, physical, and chemical properties of anthropogenic, natural, and mixed aerosols; their sources, formation, and transport mechanisms; horizontal, vertical, and temporal variations; direct and indirect effects; and interactions with the East Asian monsoon system, Particular efforts are made to advance our understanding of the mixing and interaction between dust and anthropogenic pollutants during transport. Several modeling studies were carried out to simulate aerosol impact on radiation budget, temperature, precipitation, wind and atmospheric circulation, fog, etc, In addition, impacts of the Asian monsoon system on aerosol loading are also simulated.

Rank B2C e-commerce websites in e-alliance based on AHP and fuzzy TOPSIS

Abstract: E-alliance is the union of e-commerce and its success and efficiency is related to comprehensive quality of e-commerce. Thus, ranking e-commerce websites in e-alliance is of importance, which is a multi-criteria decision-making (MCDM) problem. This paper proposes an evaluation model based on analytic hierarchy process (AHP), fuzzy sets and technique for order performance by similarity to ideal solution (TOPSIS), to tackle the issue in fuzzy environment. The AHP is applied to analyze the structure of ranking problem and to determine weights of the criteria, fuzzy sets is utilized to present ambiguity and subjectivity with linguistic values parameterized by triangular fuzzy numbers, and TOPSIS method is used to obtain final ranking. Case analysis is conducted to illustrate the utilization of the model for the problem. It demonstrates the effectiveness and feasibility of the proposed model.

Minimum error bounded efficient ℓ 1 tracker with occlusion detection

Abstract: Recently, sparse representation has been applied to visual tracking to find the target with the minimum reconstruction error from the target template subspace. Though effective, these L1 trackers require high computational costs due to numerous calculations for l 1 minimization. In addition, the inherent occlusion insensitivity of the l 1 minimization has not been fully utilized. In this paper, we propose an efficient L1 tracker with minimum error bound and occlusion detection which we call Bounded Particle Resampling (BPR)-L1 tracker. First, the minimum error bound is quickly calculated from a linear least squares equation, and serves as a guide for particle resampling in a particle filter framework. Without loss of precision during resampling, most insignificant samples are removed before solving the computationally expensive l 1 minimization function. The BPR technique enables us to speed up the L1 tracker without sacrificing accuracy. Second, we perform occlusion detection by investigating the trivial coefficients in the l 1 minimization. These coefficients, by design, contain rich information about image corruptions including occlusion. Detected occlusions enhance the template updates to effectively reduce the drifting problem. The proposed method shows good performance as compared with several state-of-the-art trackers on challenging benchmark sequences.

Numerical solution of fractional differential equations using the generalized block pulse operational matrix

Abstract: The Riemann-Liouville fractional integral for repeated fractional integration is expanded in block pulse functions to yield the block pulse operational matrices for the fractional order integration. Also, the generalized block pulse operational matrices of differentiation are derived. Based on the above results we propose a way to solve the fractional differential equations. The method is computationally attractive and applications are demonstrated through illustrative examples.

Trends in Precipitation Extremes in the Zhujiang River Basin, South China

Abstract: Spatial and temporal characteristics of precipitation trends in the Zhujiang River basin, South China, are analyzed. Nonparametric trend tests are applied to daily precipitation data from 192 weather stations between 1961 and 2007 for the following indices: annual, monthly, and daily precipitation; annual and monthly number of rain days and precipitation intensity; annual and monthly maximum precipitation; 5-day maximum precipitation, number of rainstorms with >50 mm day−1, and peaks over thresholds (90th, 95th, and 99th percentile). The results show that few stations experienced trends in the precipitation indices on an annual basis. On a monthly basis, significant positive and negative trends above the 90% confidence level appear in all months except December. Trends in the indices of monthly precipitation, rain intensity, rain days, and monthly maximum precipitation show very similar characteristics. They experience the most distinct negative (positive) trends in October (January). A change of...

Contrasting Impacts of Two-Type El Niño over the Western North Pacific during Boreal Autumn

Abstract: This work contrasts the climatic impacts of so-called warm-pool (WP) and cold-tongue (CT) El Nino on the atmospheric circulation over the western North Pacific (WNP). It is found that the anomalous atmospheric circulation over the WNP is nearly opposite in response to these two types of El Nino events in developing autumn. A weak anomalous anticyclone appears over the WNP during CT El Nino, whereas a weak anomalous cyclone emerges in the same region during WP El Nino. These nearly opposite autumn responses of atmospheric circulation have a significant impact on East Asian climate, and southern China autumn rainfall in particular, although this contrast tends to diminish as El Nino events enter their mature phase.

Probabilistic Projections of Climate Change over China under the SRES A1B Scenario Using 28 AOGCMs

Abstract: Probabilistic projection of climate change consists of formulating the climate change information in a probabilistic manner at either global or regional scale. This can produce useful results for studies of the impact of climate change impact and change mitigation. In the present study, a simple yet effective approach is proposed with the purpose of producing probabilistic results of climate change over China for the middle and end of the twenty-first century under the Special Report on Emissions Scenarios A1B (SRES A1B) emission scenario. Data from 28 coupled atmosphere–ocean general circulation models (AOGCMs) are used. The methodology consists of ranking the 28 models, based on their ability to simulate climate over China in terms of two model evaluation metrics. Different weights were then given to the models according to their performances in present-day climate. Results of the evaluation for the current climate show that five models that have relatively higher resolutions—namely, the Istitut...

The optimal priority models of the intuitionistic fuzzy preference relation and their application in selecting industries with higher meteorological sensitivity

Abstract: This paper proposes a least squares method and a goal programming method to get the priority of the intuitionistic fuzzy preference relation (IFPR). The relation between the IFPR and the interval fuzzy number preference relation (IFNPR) is established by splitting the IFPR into the membership degree interval judgment matrix and the non-membership degree interval judgment matrix. Considering the fact that the priority method must be based on the consistent condition, we propose the additive consistent conditions of the IFPR according to that of the IFNPR. However, in real-life decision situations, such consistent conditions are hard to be satisfied. For deriving the priority vector of the IFPR, the least squares model and the goal programming model are put forward. It is also shown that the same methods apply to the circumstance of group decision making. The numerical examples are provided to show that the methods proposed are valid, and the case study of selecting industries with higher meteorological sensitivity by using the intuitionistic fuzzy hierarchic structure model is given to show that the methods proposed are practical.

Delay-Slope-Dependent Stability Results of Recurrent Neural Networks

Abstract: By using the fact that the neuron activation functions are sector bounded and nondecreasing, this brief presents a new method, named the delay-slope-dependent method, for stability analysis of a class of recurrent neural networks with time-varying delays. This method includes more information on the slope of neuron activation functions and fewer matrix variables in the constructed Lyapunov-Krasovskii functional. Then some improved delay-dependent stability criteria with less computational burden and conservatism are obtained. Numerical examples are given to illustrate the effectiveness and the benefits of the proposed method.

A two-step quantum secure direct communication protocol with hyperentanglement

Abstract: We propose a two-step quantum secure direct communication (QSDC) protocol with hyperentanglement in both the spatial-mode and the polarization degrees of freedom of photon pairs which can in principle be produced with a beta barium borate crystal The secret message can be encoded on the photon pairs with unitary operations in these two degrees of freedom independently This QSDC protocol has a higher capacity than the original two-step QSDC protocol as each photon pair can carry 4 bits of information Compared with the QSDC protocol based on hyperdense coding, this QSDC protocol has the immunity to Trojan horse attack strategies with the process for determining the number of the photons in each quantum signal as it is a one-way quantum communication protocol

Deep Atmospheric Response to the Spring Kuroshio over the East China Sea

Abstract: The atmospheric response to the spring Kuroshio Front over the East China Sea is investigated using a suite of high-resolution satellite data and a regional atmospheric model. The atmospheric response appears to extend beyond the marine atmospheric boundary layer, with frequent occurrence of cumulus convection.In spring, Quick Scatterometer (QuikSCAT) wind speed shows a clear effect of sea surface temperature (SST), with high (low) wind speed observed over the warm (cold) tongue. This in-phase relationship between SST and surface wind speed is indicative of SST influence on the atmosphere. Wind convergence is found on the warmer flank of the Kuroshio Front, accompanied by a narrow rainband. The analysis of satellite-borne radar measurements indicates that deep convection appears over the Kuroshio warm tongue in the spring season, with enhanced convective precipitation, frequent occurrence of cumulus convection, and increased precipitation (cloud) tops in altitude. These deep convective activities ...

Robust quantum secure direct communication with a quantum one-time pad over a collective-noise channel

Abstract: We present two robust quantum secure direct communication (QSDC) schemes with a quantum one-time pad over a collective-noise channel. Each logical qubit is made up of two physical qubits and it is invariant over a collective-noise channel. The two photons in each logical qubit can be produced with a practically entangled source, i.e., a parametric down-conversion source with a beta barium borate crystal and a pump pulse of ultraviolet light. The information is encoded on each logical qubit with two logical unitary operations, which will not destroy the antinoise feather of the quantum systems. The receiver Bob can read out the sender’s message directly with two single-photon measurements on each logical qubit, instead of Bell-state measurements, which will make these protocols more convenient in a practical application. With current technology, our two robust QSDC schemes are feasible and may be optimal ones.

Statistical behaviours of precipitation regimes in China and their links with atmospheric circulation 1960–2005

Abstract: In this study, we comprehensively analysed daily precipitation time series of 590 rain stations in China covering 1960–2005. Ten indices were defined to evaluate changing patterns of precipitation regimes and trend detection was performed using Mann–Kendall trend test and linear regressive technique. For the sake of better understanding of underlying causes behind changing properties of precipitation regimes, we also investigated spatial and temporal variations of atmospheric circulation of water vapour flux. The results revealed different changing properties of precipitation events across China. Generally, wet tendency was identified in the south China and dry tendency in north China. Besides, slight wet tendency could be found in northwest China. In addition, increasing precipitation intensity could be observed mainly in the lower Yangtze River basin and the Pearl River basin. Remarkable seasonal shifts of wet/dry conditions were also detected in China: wet tendency in winter and dry tendency in summer. Furthermore, this study revealed good agreement between spatial distribution of precipitation regimes and water vapour flux, showing tremendous influences of water vapour flux on the precipitation changes across China. Regions east to 100°E were dominated by increasing water vapour flux in winter. Weaker East Asian Summer Monsoon was the main cause responsible for decreasing northward propagation of water vapour flux, causing different wet (dry) tendency in south (north) China. This study can provide theoretical evidence for effective water resource management and sound arrangement of agriculture activities on river basin scale under the changing environment across China. Copyright © 2010 Royal Meteorological Society

Predictable climate dynamics of abnormal East Asian winter monsoon: once-in-a-century snowstorms in 2007/2008 winter

Abstract: In 2008 (January–February), East Asia (EA) experiences the most severe and long-persisting snowstorm in the past 100 years. Results in this study show that 2007/2008 winter is dominant by the third principal mode of the East Asian winter monsoon (EAWM) which explains 8.7% of the total surface air temperature variance over EA. Significantly distinguished from the first two leading modes, the third mode positive phase features an increased surface pressure over the northwestern EA, an enhanced central Siberian high (CSH), a strengthened and northwestward extended western Pacific subtropical high (WPSH) and anomalously strong moisture transport from western Pacific, Arabian Sea and Bay of Bengal to EA. It also exhibits an intimate linkage with the sea surface temperature anomalies (SSTAs) in the Arctic Ocean areas adjacent to northern Eurasian continent, central North Pacific and northeastern Pacific. Such SSTAs emerge in prior autumn and persist through ensuing winter, signifying precursory conditions for the anomalous third EAWM mode. Numerical experiments with a simple general circulation model demonstrate that the Arctic SSTAs excite geo-potential height anomalies over northern Eurasian continent and impacts on the CSH, while the extra-tropical Pacific SSTAs deform the WPSH. Co-effects of them play crucial roles on origins of the third EAWM mode. Based on these results, an empirical model is established to predict the third mode of the EAWM. Hindcast is performed for the 1957–2008 period, which shows a quite realistic prediction skill in general and good prediction ability in the extreme phase of the third mode of the EAWM such as 2007/2008 winter. Since all these predictors can be readily monitored in real time, this empirical model provides a real time forecast tool and may facilitate the seasonal prediction of high-impact weather associated with the abnormal EAWM.

Monsoonal Influence on Typhoon Morakot (2009). Part I: Observational Analysis

Abstract: Typhoon Morakot made landfall on Taiwan with a record rainfall of 3031.5 mm during 6–13 August 2009. While previous studies have emphasized the influence of southwesterly winds associated with intraseasonal oscillations and monsoon surges on moisture supply, the interaction between Morakot and low-frequency monsoon flows and the resulting influence on the slow movement and asymmetric precipitation structure of the typhoon were examined observationally.Embedded in multi-time-scale monsoonal flows, Morakot generally moved westward prior to its landfall on Taiwan and underwent a coalescence process first with a cyclonic gyre on the quasi-biweekly oscillation time scale and then with a cyclonic gyre on the Madden–Julian oscillation time scale. The coalescence enhanced the synoptic-scale southwesterly winds of Morakot and thus decreased its westward movement and turned the track northward, leading to an unusually long residence time in the vicinity of Taiwan. The resulting slow movement and collocation...

Features of the extremely severe drought in the east of Southwest China and anomalies of atmospheric circulation in summer 2006

Abstract: The spatial-temporal features of the extremely severe drought and the anomalous atmospheric circulation in summer 2006 are analyzed based on the NCEP/NCAR reanalysis data, the characteristic circulation indices given by the National Climate Center of China, and the daily precipitation data of 20 stations in the east of Southwest China (ESC) from 1959 to 2006. The results show that the rainless period started from early June and ended in early September 2006 with a total of more than 80 days, and the rainfall was especially scarce from around 25 July to 5 September 2006. Precipitation for each month was less than normal, and analysis of the precipitation indices shows that the summer precipitation in 2006 was the least since 1959. The extremely severe drought in the ESC in summer 2006 was closely related to the persistent anomalies of the atmospheric circulation in the same period, i.e., anomalies of mid-high latitude atmospheric circulation, western Pacific subtropical high (WPSH), westerlies, South Asian high, lower-level flow, water vapor transport, vertical motion, and so on. Droughts usually occur when the WPSH lies anomalously northward and westward, or anomalously weak and eastward. The extreme drought in summer 2006 was caused by the former. When the WPSH turned stronger and shifted to the north and west of its normal position, and the South Asian high was also strong and lay eastward, downdrafts prevailed over the ESC and suppressed the water vapor transfer toward this area. At the same time, the disposition of the westerlies and the mid-high latitude circulation disfavored the southward invasion of cold air, which jointly resulted in the extremely severe drought in the ESC in summer 2006. The weak heating over the Tibetan Plateau and vigorous convective activities over the Philippine area were likely responsible for the strong WPSH and its northwestward shift in summer 2006.

The Central European limited‐area ensemble forecasting system: ALADIN‐LAEF

Abstract: The Central European limited-area ensemble forecasting system ALADIN-LAEF (Aire Limitee Adaptation Dynamique Developpement InterNational—Limited-Area Ensemble Forecasting) has been developed within the framework of ALADIN international cooperation and the Regional Cooperation for Limited-Area modelling in Central Europe (RC LACE). It was put into pre-operation in March 2007. The main feature of the pre-operational ALADIN-LAEF was the dynamical downscaling of the global ensemble forecast from the European Centre for Medium-range Weather Forecasts (ECMWF). In 2009, ALADIN-LAEF was upgraded with several methods for dealing with the forecast uncertainties to improve the forecast quality. These are: (1) the blending method, which combines the large-scale uncertainty generated by ECMWF singular vectors with the small-scale perturbations resolved by ALADIN breeding into atmospheric initial condition perturbations; (2) the multi-physics approach, wherein different physics schemes are used for different forecast members to account for model uncertainties; and (3) the non-cycling surface breeding technique, which generates surface initial condition perturbations. This article illustrates the technical details of the updated ALADIN-LAEF and investigates its performance. Detailed verification of the upgraded ALADIN-LAEF and a comparison with its first implementation (dynamical downscaling of ECMWF ensemble forecasts) are presented for a two-month period in summer 2007. The results show better performance and skill for the upgraded system due to the better representation of forecast uncertainties. Copyright © 2011 Royal Meteorological Society

An extended support vector machine forecasting framework for customer churn in e-commerce

Abstract: In order to accurately forecast and prevent customer churn in e-commerce, a customer churn forecasting framework is established through four steps. First, customer behavior data is collected and converted into data warehouse by extract transform load (ETL). Second, the subject of data warehouse is established and some samples are extracted as train objects. Third, alternative predication algorithms are chosen to train selected samples. Finally, selected predication algorithm with extension is used to forecast other customers. For the imbalance and nonlinear of customer churn, an extended support vector machine (ESVM) is proposed by introducing parameters to tell the impact of churner, non-churner and nonlinear. Artificial neural network (ANN), decision tree, SVM and ESVM are considered as alternative predication algorithms to forecast customer churn with the innovative framework. Result shows that ESVM performs best among them in the aspect of accuracy, hit rate, coverage rate, lift coefficient and treatment time. This novel ESVM can process large scale and imbalanced data effectively based on the framework.

Monthly and seasonal streamflow forecasts using rainfall‐runoff modeling and historical weather data

Abstract: [1] Well-validated rainfall-runoff models are able to capture the relationships between rainfall and streamflow and to reliably estimate initial catchment states. While future streamflows are mainly dependent on initial catchment states and future rainfall, use of the rainfall-runoff models together with estimated future rainfall can produce skilful forecasts of future streamflows. This is the basis for the ensemble streamflow prediction system, but this approach has not been explored in Australia. In this paper, two conceptual rainfall-runoff models, together with rainfall ensembles or analogues based on historical rainfall and the Southern Oscillation index (SOI), were used to forecast streamflows at monthly and 3-monthly scales at two catchments in east Australia. The results showed that both models forecast monthly streamflow well when forecasts for all months were evaluated together, but their performance varied significantly from month to month. Best forecasting skills were obtained (both monthly and 3 monthly) when the models were coupled with ensemble forcings on the basis of long-term historical rainfall. SOI-based resampling of forcings from historical data led to improved forecasting skills only in the period from September to December at the catchment in Queensland. For 3 month streamflow forecasts, best skills were in the period from April to June at the catchment in Queensland and in the period from October to January for the catchment in New South Wales, both of which were the periods after the rainy season. The forecasting skills are indicatively comparable to the statistical forecasting skills using a Bayesian joint probability approach. The potential approaches for improved hydrologic modeling through conditional parameterization and for improved forecasting skills through advanced model updating and bias corrections are also discussed.

Comparison of renewable energy policy evolution among the BRICs

Abstract: Renewable energy policy evolution of the BRICs is analyzed and assessed quantitatively based on the Bai and Perron’ s structure breaks test. Results indicate no break for time series of renewable production in Russia, while series of renewable production and consumption are characterized as segmented trend stationary processes around one or two structural breaks in Brazil, India and China. Renewable policies in Brazil and China have long-term positive effects on renewable energy production and consumption, improving the two variables’ growth rate. The time series structure change of Indian renewable energy production is complicated and the long-term impact of energy policies on renewable production is contradictory at the two breakpoints. Russian renewable policies are not working, reducing renewable energy consumption growth in the long-term. Empirical analysis suggests policy implications that China should mandate the promotion of renewable energy, develop biomass energy on the base of comparative advantage and enhance renewable energy industry chain integration.

High combustion activity of CH4 and catalluminescence properties of CO oxidation over porous Co3O4 nanorods

Abstract: The highly porous Co 3 O 4 nanorods are prepared by a simple hydrothermal method, in which CO(NH 2 ) 2 is employed as precipitating agent, and K60 (PVP, polyvinylpyrrolidone) is used as surfactant to improve the stability of the nanoparticles. For comparison, the bulk Co 3 O 4 is prepared by thermal decomposition of cobalt nitrate. The samples are characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (ED), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, N 2 adsorption, Thermogravimetric analysis (TG), H 2 -temperature programmed reduction (TPR), CO-, CH 4 -, and O 2 -temperature programmed desorption (TPD). The catalluminescence (CTL) and catalytic properties of the samples are investigated extensively. The results show that the Co 3 O 4 nanorods are composed of nanoparticles, and have a large number of pores with a narrow pore size distribution (1.5–7 nm). Compared with the bulk Co 3 O 4 , the porous nanorods have a higher CTL intensity of CO oxidation, and a higher activity of CH 4 combustion especially at a higher gas hourly space velocity (GHSV), which has been ascribed to its porous structure and larger surface area.