Environmental Conditions Determining the Timing of the Lifetime Maximum Intensity of Tropical Cyclones over the Western North Pacific and Their Frequency of Occurrence

Environmental conditions determining the timing of the lifetime maximum intensities of tropical cyclones(TCs)are investigated for the TCs over the western North Pacific during the period 2008-2017.The results show that the land controls the timings of the lifetime maximum intensities in 42% of the TCs over this basin,indicating that accurate track forecasts are beneficial for TC intensity forecasts.With respect to other TCs that are not affected by the land(i.e.,Ocean-TCs),the timings of their lifetime maximum intensities are determined by multiple oceanic factors.In particular,interactions between TCs and cold-core eddies occur in a large proportion(nearly 60%)of Ocean-TCs at or shortly after the times of their lifetime maximum intensities,especially in strong TCs(categories 4 and 5),suggesting that a consideration of the above interactions is necessary for improving TC intensity forecasting skills.In addition,unfavorable oceanic heat content conditions become common as the latitude increases over 25°N,influencing half of the Ocean-TCs.Strong vertical wind shear contributes detrimentally to the atmospheric environment in 17% of the TCs over this basin,especially in moderate and weak TCs.In contrast,neither the maximum potential intensity nor the humidity in the middle level of the atmosphere plays dominant roles when TCs turn from their peak intensities to weakening.

A discussion of the bi-directional ranking of occurrence-frequency based non-interactive literature method for knowledge discovery

Based on the analysis of the existing ranking terminology or subject relevancy of documents methods through an intermediary collection as a catalyst(designated as Group B collection) for the purpose of of non-interactive literature-based discovery, this article proposes a bi-directional document occurrence frequency based ranking method according to the 'concurrence theory' and the degree and extent of the subject relevancy. This method explores and further refines the ranking method that is based on the occurrence frequency of the usage of certain terminologies and documents and injects a new insightful perspective of the concurrence of appropriate terminologies/documents in the 'low occurrence frequency component' of three non-interactive document collections. A preliminary experiment was conducted to analyze and to test the significance and viability of our newly designed operational method.

On Spatiotemporal Characteristics of Sea Fog Occurrence over the Northern Atlantic from 1909 to 2008

In this paper, the International Comprehensive Ocean and Atmosphere Data Set(ICOADS) is utilized to investigate the horizontal distribution of sea fog occurrence frequency over the Northern Atlantic as well as the meteorological and oceanic conditions for sea fog formation. Sea fog over the Northern Atlantic mainly occurs over middle and high latitudes. Sea fog occurrence frequency over the western region of the Northern Atlantic is higher than that over the eastern region. The season for sea fog occurrence over the Northern Atlantic is generally from April to August. When sea fogs occur, the prevailing wind direction in the study area is from southerly to southwesterly and the favorable wind speed is around 8 m s-1. It is most favorable for the formation of sea fogs when sea surface temperature(SST) is 5℃ to 15℃. When SST is higher than 25℃, it is difficult for the air to get saturated, and there is almost no report of sea fog. When sea fogs form, the difference between sea surface temperature and air temperature is mainly-1 to 3℃, and the difference of 0℃ to 2℃ is the most favorable conditions for fog formation. There are two types of sea fogs prevailing in this region: advection cooling fog and advection evaporating fog.

Occurrence and Distribution of Alternanthera philoxeroides in the Youjiang River Valley

The occurrence and distribution of Alternanthera philoxeroides in different habitats of four districts and counties in the Youjiang River Valley were investigated from September to November in 2018. The results show that A. philoxeroides certainly has occurred in watercourses, ridges, ditches, roadsides and green belts in those four districts and counties of The Youjiang valley. According to the sampling investigation, ridges have the highest frequency of occurrence, followed by ditches and roadsides. The A. philoxeroides living in ditches grows better than other four habitats, and the plants are stronger and vigorous. In the geographical division, the distribution areas of A. philoxeroides in Tianyang District and Tiandong County are the largest. Youjiang District and Pingguo County have a small amount of A. philoxeroides distributed along farmland, green belts and village houses, which has the characteristics of high local population density and strong aggregation, but the areas are smaller than other counties.

Variability of Tropical Cyclone in High Frequent Occurrence Regions over the Western North Pacific

In this study, three high frequent occurrence regions of tropical cyclones(TCs), i.e., the northern South China Sea(the region S), the south Philippine Sea(the region P) and the region east of Taiwan Island(the region E), are defined with frequency of TC's occurrence at each grid for a 45-year period(1965–2009), where the frequency of occurrence(FO) of TCs is triple the mean value of the whole western North Pacific. Over the region S, there are decreasing trends in the FO of TCs, the number of TCs' tracks going though this region and the number of TCs' genesis in this region. Over the region P, the FO and tracks demonstrate decadal variation with periods of 10–12 year, while over the region E, a significant 4–5 years' oscillation appears in both FO and tracks. It is demonstrated that the differences of TCs' variation in these three different regions are mainly caused by the variation of the Western Pacific Subtropical High(WPSH) at different time scales. The westward shift of WPSH is responsible for the northwesterly anomaly over the region S which inhibits westward TC movement into the region S. On the decadal timescale, the WPSH stretches northwestward because of the anomalous anticyclone over the northwestern part of the region P, and steers more TCs reaching the region P in the greater FO years of the region P. The retreating of the WPSH on the interannual time scale is the main reason for the FO's oscillation over the region E.

Spatio-temporal Variations in Drought with Remote Sensing from the Mongolian Plateau During 1982–2018

The Mongolian Plateau is one of the regions most sensitive to climate change,the more obvious increase of temperature in 21 st century here has been considered as one of the important causes of drought and desertification.It is very important to understand the multi-year variation and occurrence characteristics of drought in the Mongolian Plateau to explore the ecological environment and the response mechanism of surface materials to climate change.This study examines the spatio-temporal variations in drought and its frequency of occurrence in the Mongolian Plateau based on the Advanced Very High Resolution Radiometer(AVHRR)Normalized Difference Vegetation Index(NDVI)(1982–1999)and the Moderate-resolution Imaging Spectroradiometer(MODIS)(2000–2018)datasets;the Temperature Vegetation Dryness Index(TVDI)was used as a drought evaluation index.The results indicate that drought was widespread across the Mongolian Plateau between1982 and 2018,and aridification incremented in the 21 st century.Between 1982 and 2018,an area of 164.38×10^4 km^2/yr suffered from drought,accounting for approximately 55.28%of the total study area.An area of approximately 150.06×10^4 km^2(51.43%)was subject to more than 160 droughts during 259 months of the growing seasons between 1982 and 2018.We observed variable frequencies of drought occurrence depending on land cover/land use types.Drought predominantly occurred in bare land and grassland,both of which accounting for approximately 79.47%of the total study area.These terrains were characterized by low vegetation and scarce precipitation,which led to frequent and extreme drought events.We also noted significant differences between the areal distribution of drought,drought frequency,and degree of drought depending on the seasons.In spring,droughts were widespread,occurred with a high frequency,and were severe;in autumn,they were localized,frequent,and severe;whereas,in summer,droughts were the most widespread and frequent,but less severe.The increase in temperature,decrease in precipitation,continuous depletion of snow cover,and intensification of human activities have resulted in a water deficit.More severe droughts and aridification have affected the distribution and functioning of terrestrial ecosystems,causing changes in the composition and distribution of plants,animals,microorganisms,conversion between carbon sinks and carbon sources,and biodiversity.We conclude that regional drought events have to be accurately monitored,whereas their occurrence mechanisms need further exploration,taking into account nature,climate,society and other influencing factors.

Detection of the Kuroshio frontal instable processes (KFIP) in the East China Sea using the MODIS images

The Kuroshio frontal instable processes （KFIP） in the East China Sea （ECS） not only have a great impact on the hydrologic characteristics,the pollutants drift,the distribution of seafloor sediment and the ships navigation of the ECS,but also are closely related to the climate changes of the coastal areas of the ECS.However the frequency and area of occurrence of the KFIP have not been studied fully and detailedly.Because of its high spatial and temporal resolution,MODIS data is a kind of very good data source for surveying and researching the KFIP in the ECS.The aim of this study is to detect the KFIP in the ECS by using MODIS data,and to study the frequency and region of occurrence of the KFIP in the ECS.The selection has coverage of level 2 data of MODIS SST and Kd490 ranging from July 1,2002 to June 30,2009 of the ECS when there was no cloud impact or little.By using of the data,the minimum standard of the Kuroshio temperature fronts and the diffuse attenuation coefficient （Kd490） fronts of the ECS are given.Based on these standards and the curvature distinguish methods,the standard of curvature distinguish for the KFIP in the ECS are put forward.By making use of this standard,we study a total of 2073 satellite-derived images,and discover that as long as there is no cloud impact from January to May and October to December,the KFIP in the ECS are surely found in MODIS satellite images.From June to September,the frequency of occurrence can also reach to 82.9% at least.Moreover,it is obtained that there are three source regions of these instability processes,namely,（26°N,121.5°E） nearby,（27°N,125°E） nearby and （30°N,128°E） nearby.The differences of the characteristics of these instability processes which are generated in different regions are analyzed in the present study.

Hydrogen Bonds of C=S, C=Se and C=Te with C-H in Small-Organic Molecule Compounds Derived from the Cambridge Structural Database (CSD)

Considerable interest in hydrogen bonding involving chalcogen has been growing since the IUPAC committee has redefined hydrogen bonding. Not only the focus is on unconventional acceptors, but also on donors not discussed before. It has been mentioned in previous studies that the proton of the H-C group could be involved in hydrogen bonding, but with conventional acceptors. In this study, we explored the ability of hydrogen bond formation of Se, S and Te acceptors with the H-C donor using Cambridge Structural Database in conjunction with Ab Initio calculations. In the CSD, there are respectively 256, 6249 and 11 R1,R2,-C=Se, R1,R2,-C=S and R1,R2,-C=Te structures that form hydrogen bonds, in which the N,N groups are majority. Except for C=S acceptor which can form a hydrogen bond with its C, C group, both C=Se and C=Te acceptors could form a hydrogen bond only with N,C and N,N groups. CSD analysis shows very similar d (norm) around -0.04 Å, while DFT-calculated interaction for N,C and N,N groups are also similar. Both interaction distances derived from CSD analysis and DFT-calculated interaction energies demonstrate that the acceptors form stable complexes with H-CF3. Besides hydrogen bonds, dispersion interactions are forces stabilizing the complexes since their contribution can reach 50%. Analysis of intra-molecular geometries and Ab Initio partial charges show that this bonding stems from resonance induced Cδ+=Xδ- dipoles. In many respects, both C=Se, C=S and C=Te are similar to C=S, with similar d (norm) and calculated interaction strengths.

Fundamental Characteristics of Tropical Rain Cell Structures as Measured by TRMM PR

Rain cells are the most elementary unit of precipitation system in nature.In this study,fundamental geometric and physical characteristics of rain cells over tropical land and ocean areas are investigated by using 15-yr measurements of the Tropical Rainfall Measuring Mission(TRMM)Precipitation Radar(PR).The rain cells are identified with a minimum bounding rectangle(MBR)method.The results indicate that about 50%of rain cells occur at length of about 20 km and width of 15 km.The proportion of rain cells with length>200 km and width>100 km is less than1%.There is a a log-linear relationship between the mean length and width of rain cells.Usually,for the same horizontal geometric parameters,rain cells tend to be square horizontally and lanky vertically over land,while vertically squatty over ocean.The rainfall intensity of rain cells varies from 0.4 to 10 mm h-1 over land to 0.4–8 mm h-1 over ocean.Statistical results indicate that the occurrence frequency of rain cells decreases as the areal fraction of convective precipitation in rain cells increases,while such frequency remains almost invariant when the areal fraction of stratiform precipitation varies from 10%to 80%.The relationship between physical and geometric parameters of rain cells shows that the mean rain rate of rain cells is more frequently associated with the increase of their area,with the increasing rate over land greater than that over ocean.The results also illustrate that heavy convective rain rate prefers to occur in larger rain cells over land while heavy stratiform rain rate tends to appear in larger rain cells over ocean.For the same size of rain cells,the areal fraction and the contribution of convective precipitation are about10%–15%higher over land than over ocean.

Similarity Estimation Between DNA Sequences Based on Local Pattern Histograms of Binary Images

Graphical representation of DNA sequences is one of the most popular techniques for alignment-free sequence comparison. Here, we propose a new method for the feature extraction of DNA sequences represented by binary images, by estimating the similarity between DNA sequences using the frequency histograms of local bitmap patterns of images. Our method shows linear time complexity for the length of DNA sequences, which is practical even when long sequences, such as whole genome sequences, are compared. We tested five distance measures for the estimation of sequence similarities, and found that the histogram intersection and Manhattan distance are the most appropriate ones for phylogenetic analyses.

Species abundance distributions as a proxy for the niche-neutrality continuum

Aims Species abundance distributions(SADs)are often used to verify mechanistic theories underlying community assembly.However,it is now accepted that SADs alone are not sufficient to reveal biological mechanisms.Recent attention focuses on the relative importance of stochastic dispersal processes versus deterministic processes such as interspecific competition and environmental filtering.Here,we combine a study of the commonness and rarity of species(i.e.the SAD)with mechanistic processes underlying community composition.By comparing the occurrence frequen-cies of each and every species with its abundance,we quantify the relative contributions of common and rare species to the maintenance of community structure.Essentially,we relate the continuum between commonness and rarity with that of niches and neutrality.Methods An individual-based,spatially explicit model was used to simu-late local communities in niche spaces with the same parameters.We generated sets of assemblages from which species were elim-inated in opposing sequences:from common to rare and from rare to common,and investigated the relationship between the abundance and frequency of species.We tested the predictions of our model with empirical data from a field experiment in the environmentally homogeneous alpine meadows of the Qinghai-Tibetan plateau.Important Findings Our simulations support the widespread notion that common species maintain community structure,while rare species maintain species diversity,in both local and regional communities.Our results,both from theoretical simulations and from empirical observations,revealed positive correlations between the abundance of a particular species and its occurrence frequency.SAD curves describe a continuum between commonness and rarity.Removing species from the‘rare’end of this continuum has little effect on the similarity of communities,but remov-ing species from the‘common’end of the continuum causes significant increases in beta diversity,or species turnover,between communities.In local communities distributed in a homogenous habitat,species located at the‘common’end of the continuum should be selected by environmental filtering,with niche space partitioning governed by interspecific competition.Conversely,species located at the‘rare’end of the continuum are most likely subject to stochastic dispersal pro-cesses.Species situated at intermediate locations on this continuum are therefore determined by niche and neutral processes acting together.Our results suggest that,in homogeneous habitats,SAD curves describ-ing the common-rare continuum may also be used to describe the con-tinuum between niches and neutrality.

Web-Based Biomedical Literature Mining

With an upsurge in biomedical literature,using data-mining method to search new knowledge from literature has drawing more attention of scholars.In this study,taking the mining of non-coding gene literature from the network database of PubMed as an example,we first preprocessed the abstract data,next applied the term occurrence frequency(TF) and inverse document frequency(IDF)(TF-IDF) method to select features,and then established a biomedical literature data-mining model based on Bayesian algorithm.Finally,we assessed the model through area under the receiver operating characteristic curve(AUC),accuracy,specificity,sensitivity,precision rate and recall rate.When 1 000 features are selected,AUC,specificity,sensitivity,accuracy rate,precision rate and recall rate are 0.868 3,84.63%,89.02%,86.83%,89.02% and 98.14%,respectively.These results indicate that our method can identify the targeted literature related to a particular topic effectively.

The classification of handwriting features of the Kazakh language written in Latin script

In 2017,the Republic of Kazakhstan began the phased transition of its alphabet from Cyrillic to Latin script.This transition has presented significant challenges to Kazakhstani document examiners,who have yet to develop appropriate methodologies for the analysis of handwriting samples written in the Kazakh language using Latin letters.This study aims to identify distinguishing macro and micro features of letters within Kazakh writing samples produced using the Latin alphabet and determine their frequencies of occurrence and discriminating power indices.Micro features were examined using the four most frequently appearing letters:“a”,“y”,“e”and“n”.A comparative analysis of tested Latin letters with those of a similar configuration in Cyrillic demonstrated differences in the number of distinguishing features,as well as in the frequency of occurrence and discriminating power indices of similar features.These results show that separate statistical bases should be used for Latin and Cyrillic letters when analysing handwriting samples based on the frequencies of occurrence of micro and macro writing features.