Failure characteristics and fracture mechanism of overburden rock induced by mining:A case study in China

This study employs similar simulation testing and discrete element simulation coupling to analyze the failure and deformation processes of a model coal seam's roof.The caving area of the overburden rock is divided into three zones:the delamination fracture zone,broken fracture zone,and compaction zone.The caving and fracture zones'heights are approximately 110 m above the coal seam,with a maximum subsidence of 11 m.The delamination fracture zone's porosity range is between 0.2 and 0.3,while the remainder of the roof predominantly exhibits a porosity of less than 0.1.In addition,the numerical model's stress analysis revealed that the overburden rock's displacement zone forms an'arch-beam'structure starting from 160 m,with the maximum and minimum stress values decreasing as the distance of advancement increases.In the stress beam interval of the overburden rock,the maximum value changes periodically as the advancement distance increases.Based on a comparative analysis between observable data from on-site work and numerical simulation results,the stress data from the numerical simulation are essentially consistent with the actual results detected on-site,indicating the validity of the numerical simulation results.

Quantitative Study on Morphological Change Characteristics of Tonle Sap Lake Based on DEM

Lake is an important part of the natural ecosystem, and its morphological characteristics reflect the capacity of lake regulation and storage, the strength of material migration, and the characteristics of shoreline development. In most existing studies, remote sensing images are used to quantify the morphological characteristics of lakes. However, the extraction accuracy of lake water is greatly affected by cloud cover and vegetation cover, and the inversion accuracy of lake elevation data is poor, which cannot accurately describe the response relationship of lake landscape morphology with water level change. Therefore, this paper takes Tonle Sap Lake as the research object, which is the largest natural freshwater lake in Southeast Asia. DEM is constructed based on high-resolution measured topographic data, and morphological indicators such as lake area, lake shoreline length, perimeter area ratio, longest axis length, maximum width, shoreline development index, lake shape complexity, compactness ratio and form ratio are adopted to researching the evolution law of high water overflows and low water outbursts quantitatively, and clarifying the variation characteristics of landscape morphology with water level gradient in Tonle Sap Lake. The research results have important theoretical significance for the scientific utilization of Tonle Sap Lake water resources and the protection of the lake ecosystem.

Variation Characteristics and Tendency of Precipitation in Chaoyang Area between 1908 and 2008

According to the precipitation sequence of Beijing City from 1900 to 1958,the precipitation sequence of Chengde City were revised and extended.Then the precipitation sequence of Chaoyang City were revised and extended with the precipitation sequence of Chengde City to form 100-years precipitation sequence of Chaoyang.The results showed that the 100-years precipitation sequence of Chaoyang indicated a decreasing trend and obvious periodic variation with the change of age.That is,a 10-year rainy period (approximately 525.0 mm) appeared every 30 a,while the 30-year drought period was approximately 460.0 mm,65.0 mm lower than the former.Moreover,an obviously heavy drought lasting for 2-4 a appeared every 20 a.

Spatiotemporal Variation Characteristics of Water Quality in the Yinma River

As an important river in the central part of Jilin Province, the Yinma River plays a crucial role in the daily lives of the people in Jilin Province. In this paper, 15 cross sections were selected in the Yinma River basin. Based on the water quality monitoring data from 2012 to 2021, referring to the Environmental Quality Standards for Surface Water (GB 3838-2002) and historical monitoring data of the river, dissolved oxygen (DO), five-day biochemical oxygen demand (BOD 5), permanganate index (COD Mn ), chemical oxygen demand (COD), ammonia nitrogen (NH 4-N), total phosphorus (TP), and total nitrogen (TN) were determined as 7 evaluation indicators, and the water quality of 15 cross sections in the Yinma River basin was comprehensively evaluated. A characteristic analysis was conducted on the water quality of the Yinma River, and its pollution sources were identified. Based on the conclusions, constructive control measures were proposed.

Geographic variation and genetic performance of Picea koraiensis in growth and wood characteristics

Eight provenances of 19-year-old Picea koraiensis Nakai from the provenancetrials of Maoershan (45°20′N, 127°30′E), Liang-shui (47°10′N, 128°53′E) and Jiagedaqi(50°24′N, 124°07′E) in Northeast China were investigated to analyze the genetic variation ingrowth characteristics (tree height and diameter) and wood characteristics (tracheid length,tracheid diameter, tracheid wall thickness, annual ring width as well as wood density). Greatvariation in height growth and breast height diameter growth was observed among the provenances, andalong with the increase of tree age, these provenances presented different geographic adaptability.The growth characteristics of Picea koraiensis stand at age of 10 in Maoershan and Liangshuiprovenance trials had a positive correlation with longitude, and with increase of tree age to 15 and19, the tree growth of the provenances displayed a significant positive correlation with latitudeas well as altitude. For wood characteristics, great variation was also found among the provenances.There exists a close relation between growth characteristics and wood properties of the provenance.The height and breast height diameter growth of the provenance had a positive correlation withtracheid diameter and annual ring width, and a negative correlation with tracheid wall thickness andwood density. Genetic performance of the provenance in all above characteristics was alsoinvestigated in order to provide more useful information for comprehensive selection of this speciesfor pulpwood and plywood production.

Analysis on the Variation Characteristics of Temperature and Precipitation in Benxi Area under the Background of Climate Warming

[Objective] The research aimed to study the variation characteristics of temperature and precipitation in Benxi area under the background of climate warming.[Method] Based on the monthly mean temperature and precipitation data of four routine meteorological stations in Benxi area from 1953 to 2010,by using linear tendency rate,linear regression equation,wavelet analysis,Mann-Kendall detection and so on,the variation characteristics of temperature and precipitation under the background of climate warming in the area were analyzed.[Result] The annual average temperature during 1953-2010 in Benxi area presented rise trend,and the linear tendency rate was 0.28 ℃/10 a.It was temperature increase trend in four seasons.The temperature rise rate in winter was the maximum and was the minimum in summer.The annual rainfall presented decrease trend,and the linear tendency rate was-18.16 mm/10 a.Except in spring,it was decrease trend in other seasons.Mann-Kendall mutation detection showed that the mutation of annual average temperature in Benxi area in recent 58 years appeared in 1986.There was no mutation phenomenon in summer.Spring mutation appeared in 1974,and autumn mutation appeared in 1987.Winter mutation was in 1981.The annual and seasonal precipitation didn’t have the mutation phenomenon.The wavelet analysis found that the annual average temperature had the periodic variations of 12-14,5-6 and 2 years in Benxi area in recent 58 years.The annual rainfall had the periodic fluctuations of 8-12,5-6 and 2 years.[Conclusion] The research provided the scientific basis for exploration and sustainable development of the climate resources in the mountain area.

Interannual Variability and Scenarios Projection of Sea Ice in Bohai Sea Part Ⅰ: Variation Characteristics and Interannual Hindcast

The Bohai Sea is one of the southernmost areas for sea ice formation in the northern hemisphere.Sea ice disasters in this body of water severely affect marine activities and the safety of coastal residents.In this study,we analyze the variation characteristics of the sea ice in the Bohai Sea and establish an annual regression model based on predictable mode analysis method.The results show the following:1)From 1970 to 2018,the average ice grade is(2.6±0.8),with a maximum of 4.5 and a minimum of 1.0.Liaodong Bay(LDB)has the heaviest ice conditions in the Bohai Sea,followed by Bohai Bay(BHB)and Laizhou Bay(LZB).Interannual variation is obvious in all three bays,but the linear decreasing trend is significant only in BHB.2)Three modes are obtained from empirical orthogonal function analysis,namely,single polarity mode with the same sign of anomaly in all of the three bays and strong interannual variability(82.0%),the north–south dipole mode with BHB and LZB showing an opposite sign of anomalies to that in LDB and strong decadal variations(14.5%),and a linear trend mode(3.5%).Critical factors are analyzed and regression equations are established for all the principal components,and then an annual hindcast model is established by synthesizing the results of the three modes.This model provides an annual spatial prediction of the sea ice in the Bohai Sea for the first time,and meets the demand of operational sea ice forecasting.

Analysis of the carbon dioxide mole fraction variation and its transmission characteristics in Taiyuan

Based on the concentrations of CO2,PM2.5 and PM1.0,and conventional meteorological observation data from 2016 to 2018 at Taiyuan station,which belongs to the Shanxi greenhouse gas observation network,the CO2 concentration monthly and daily distribution characteristics,the weekend effect,and the variation characteristics on haze days and non-haze days,are analyzed.By using the Hybrid Single-Particle Lagrangian Integrated Trajectorymodel(backward trajectory model)and surface wind data,the transmission characteristics of atmospheric CO2 in Taiyuan are studied in various seasons.The results show that,in Taiyuan,the CO2 mole fraction in autumn and winter is higher than that in spring and summer,and on haze days is higher than that on non-haze days.The diurnal variation characteristic of CO2mole fraction in each season is‘single peak and single valley’with the peak value around 0700(hereafter refers to Beijing Time)and the valley value around 1600.The CO2 mole fraction on workdays is slightly higher than that on non-workdays and obviously different around 0800 of the early peak.Horizontal diffusion can reduce the CO2 mole fraction,while breezy weather is not beneficial to CO2 diffusion.The wind direction and speed in the upper levels are different from those near the surface,and the close air masses in the southwest–west–northwest sector raise the CO2 concentration in Taiyuan obviously.This indicates that the CO2 in Taiyuan is mainly contributed by local sources.

Dynamic Variation Characteristics of Phosphorus in Paddy Field Runoff in Saline Land and Its Potential Environmental Effect

[Objective] The aim was to study the dynamic variation characteristics of phosphorus in paddy field runoff in saline land and its potential environmental effect. [Method] Taking Qianguo irrigation district in soda-saline land in Songnen Plain as study object, the dynamic variation law of phosphorus in paddy field runoff under different irrigation conditions and its potential environmental effect were discussed. [Result] Surface water in paddy field was alkaline, and scattered soil had poor fertilizer conservation capacity. Phosphorus accumulated in soil surface, which could increase the risk of phosphorus loss. Phosphorus loss in paddy field mainly occurred in irrigation period and runoff period caused by rainstorm. The concentration of total phosphorus (TP), particulate phosphorus (PP), total dissolved phosphorus (TDP) and dissolved reactive phosphorus (DRP) in paddy field runoff decreased with time, especially PP. Phosphorus concentration exceeded critical value and resulted to eutrophication, which threatened the water quality security of Chagan Lake. Phosphorus concentration in water recession canal increased with time, and eutrophication with different degrees appeared under high temperature. TP concentration in surface water of paddy field was highly negatively correlated with that in water recession canal, and the correlation coefficients R2(α=0.05)in three paddy fields were 0.850 9, 0.896 4 and 0.915 3, respectively. The pollution load of phosphorus in paddy field with the best irrigation condition was higher, and its pollution risk was the highest. Thus, such fields should be monitored and controlled mainly as the critical source area of phosphorus loss. [Conclusion] The study could provide theoretical foundations for developing saline land rationally, establishing optimal management measure of phosphorus in saline land and controlling phosphorus loss from farmland to protect local water resources.

INTENSITY INDEX OF SOUTH CHINA SEA MONSOON AND ITS VARIATION CHARACTERISTICS

According to the basic characteristics of the activities of summer monsoon in the South China Sea, a standardized index, sI, has been designed that integrates a dynamic factor (southwesterly component) and a thermodynamic factor (OLR) for the indication of summer monsoon in the South China Sea. With the index determined for individual months of June, July and August and the entire summertime from 1975 to 1999, specific months and years are indicated that are either strong or weak in monsoon intensity. The variation is studied for the patterns and sI抯 relationship is revealed with the onset of summer monsoon and the precipitation in Guangdong province and China. The results show that there are quasi-10 and quasi-3-4 year cycles in the interannual variation of the monsoon over the past 25 years. When it has an early (late) onset, the summer monsoon is usually strong (weak). In the strong (weak) monsoon years, precipitation tends to be more (less) in the first raining season of the year but normal or less (normal) in the second, in the province, but it would be more (less) in northeastern China and most parts of the northern China and south of the lower reaches of the Changjiang River and less (more) in the middle and lower reaches of the river, western part of northern China and western China.

VARIATION CHARACTERISTICS OF TROPICAL CYCLONES MAKING LANDFALL IN CHINA AT DIFFERENT INTENSITIES

According to the national standard(2006)on tropical cyclone(TC)intensity,TCs are categorized into six intensity types,namely,tropical depression(TD),tropical storm(TS),severe tropical storm(STS), typhoon(TY),severe typhoon(STY),and super severe typhoon(SSTY).Fifty-eight years(1949–2006)of the datasets from the Yearbook of Typhoons and Yearbook of Tropical Cyclones were used to study the variation characteristics of TCs making landfalls in China's Mainland,Hainan and Taiwan islands.The main results are as follows.First,interannual or interdecadal variations in the number of landfalling TCs at different intensities exist.As far as long-term trends are concerned,the TD and TS frequencies show a significant linearly decreasing trend while those of STY show a significant linearly increasing trend.Second, a significant period of 6–8 years exist in the variations of annual landfalling TD,TS,and STS frequencies while quasi-16-year periods are found in the annual TY frequency.Third,TD and TS are generated mostly over the South China Sea,while TY,STY,and SSTY mostly over the waters southeast of the Bashi Channel and the ocean to the east of the Philippines.Fourth,as far as interdecadal trends are concerned,the frequencies of landfalling TD and TS generated over the South China Sea show significant linearly decreasing trends.However,TY and STY show significant linearly increasing trends.

Analysis on temporal and spatial variations of groundwater hydrochemical characteristics in the past decade in southern plain of Beijing, China

Groundwater utilization and protection are crucial for sustainable urban development. This is especially true for Beijing, where groundwater is an important source for urban water supply. In this study, statistical methods, including descriptive statistics, correlation analysis, principal component analysis, and Piper-Tri-linear diagram, were used in analyzing the temporal and spatial variations of the hydrochemical characteristics of groundwater based on monitored data from the southern plain of Beijing, China. Results indicated consistent changes of groundwater's hydrochemical characteristics in different aquifers in the study area. The percentage of HCO_3^-in total anion increased significantly in the groundwater, and hydrochemical water type evolved gradually from Ca-Mg-Cl-SO_4 based to Ca-Mg-HCO_3 based from period 2005-2007 to period 2013-2015. In shallow groundwater, the concentration of Na^+, Ca^(2+), SO_4^(2-), HCO_3^-, and total dissolved solids(TDS) increased from period 2005-2007 to period 2013-2015, and the greatest change came from HCO_3^-, rising from 428.93 to 528.96 mgL^(-1). The changes of main ionic concentrations in the deep groundwater were consistent with those in the shallow groundwater for both periods. However, the variations in deep groundwater were less than those in shallow groundwater. The temporal and spatial variations of hydrochemical characteristics reflect the groundwater quality in the study area. This study could facilitate decision-making process on the protection of groundwater resources to ensure its sustainable utilization.

Spatial and Temporal Variation Characteristics of Gale Days in China from 1961 to 2016

Based on data of hail days at 2 481 stations during 1961-2016,the temporal and spatial distribution characteristics and periodic variation of gale days in China and seven geographical regions were analyzed by using a variety of statistical methods. The results showed that: in time,the gale days in China and the seven geographical areas all showed a decreasing trend from 1961 to 2016. In the Tibet( Southeast China and Southwest China) region,the annual number of single-station gale days was the most( least),but the decrease ratio was the least( most). In the significance oscillation period,it was 14 years in the whole country,60 years in Northeastern China,Northern China and east part of Northwestern China,7,14 and 60 years in the west of Northwestern China,Southwestern China and Southeastern China,7 and 60 years in the Tibet region. The mutation of gale days generally occurred in 1991,1993,1989,1997,1986,1997,1992 and 1984 in the whole country,Northeastern China,Northern China,east part of Northwestern China,west part of Northwestern China,Tibet,Southwestern China and Southeastern China,but only the east of Northwestern China and Tibet region passed 0. 05 of significance test. In space,the annual average gale days showed the pattern of southeast low and northwest high in China from 1961 to 2016. The annual average gale days were more abundant in the central and western Tibet,the southern Qinghai,eastern Xinjiang,western Sichuan,northern Inner Mongolia and northern Gansu. These regions were dominated by positive anomaly in the 1970 s and the 1980 s,but negative in other decades. Annual gale days in most regions of China showed a decreasing trend during 1961-2016,and fluctuation presented high in east region and low in west region beside " Hu Huanyong line".

Variation Characteristics and Mutation Analysis of the Temperature in Fangchenggang of Guangxi in Recent 55 Years

[Objective] The research aimed to analyze change characteristics and mutation situation of the temperature in Fangchenggang of Guangxi from 1955 to 2009. [Method] Based on actual temperature observation data in Fangchenggang of Guangxi from 1955 to 2009, by using linear trend estimation, Mann-Kendall and cumulative anomaly, change characteristics and mutation situation of the temperature in the city in recent 55 years were analyzed. [Result] Annual average temperature had an obvious rising trend in Fangchenggang in recent 55 years, which was basically consistent with that in whole country. Summer, autumn and winter average temperatures all had obvious warming trends except that the trend in spring. Summer, winter and annual average temperature jumps occurred in the 1980s. Autumn average temperature jump occurred in the end of 1970s while spring average temperature had no jump. The situation in winter was that a transition from low stage to high stage happened in the middle period of 1980s, while transitions of the annual, spring, summer and autumn average temperatures from low stage to high stage happened in the middle and later periods of 1990s. [Conclusion] The research provided decision-making basis for going after advantages and avoiding disadvantages, guiding agricultural production and using climate resource in the zone sufficiently and reasonably.

Analysis of Relation between Variation Characteristics and Climatic Influencing Factors of Shallow Ground Temperature in Shijiazhuang

Based on the daily observation data of shallow ground temperature, total cloud cover, precipitation, evaporation capacity and frozen soil of 5 stations in Shijiazhuang from 1981 to 2010, using methods such as linear trend and complete correlation coefficient, relation between variation characteristics and climatic influencing factors of shallow ground temperature was analyzed to lay the foundation for studying impact factors of shallow ground temperature and provide references for daily maintenance of automatic observation business. The results showed that fluctuant variability and fluctuant range of mean shallow layer ground temperature in Shijiazhuang became smaller with soil layer being deeper for all years and seasons, and the fluctuant variability was maximal in spring and minimal in winter, while the fluctuant range was maximal in summer and minimal in winter; mean shallow layer ground temperature for all years had a warming trend with an obvious warming trend in winter, and warming range in winter was smaller and the extent was weaker with soil layer being deeper while a cooling trend occurred in summer; there was a coincident trend between total cloud cover at night and shallow ground temperature in winter, and between evaporation capacity and shallow ground temperature in summer, while there was an inconsistent trend between maximum depth of frozen soil, period of freezing weather and shallow ground temperature in winter, and between total cloud cover in the davtime, orecioitation and shallow around temperature in summer.

Study on Temporal and Spatial Characteristics of Climate Variation in Hebei Area during 1956-2007

[Objective] The research aimed to study temporal and spatial characteristics of climate variation in Hebei area during 1956-2007. [Method] Based on the data from 23 weather stations evenly distributed over Hebei area (included Beijing and Tianjin) during 1956-2007, by using statistical analytic method, the temporal and spatial variation characteristics of main meteorological factors (temperature and precipitation, etc.) in the area were analyzed. The variation fact and evolution rule of climate in the area in 52 years were discussed. [Result] In Hebei area during 1956-2007, the annual and four-season temperatures both presented wavy rise trends. The temperature increment in winter was the maximum, contributing the most to the annual temperature elevation in this area. The temperatures in the whole district all presented rise trends, and the variation difference had regularity. The annual and four-season rainfalls both had large fluctuation amplitudes, following different linear variation trends. The annual rainfall overall presented wavy decrease trends. The spatial difference of rainfall variation was significant. The rainfalls in the whole district all presented decrease trends. The decrease amplitude presented low-high-low pattern from the northeast to the southwest. The potential evaporation capacity over the whole district was the highest in the 1960s, and decreased ever since instead of increasing with the temperature. The potential evaporation capacities of each season also presented decline trends. Except in Fengning and Yuxian, the evaporation capacities of other stations in the whole district all presented decline trends. The relative humidity slightly decreased as time, with the exception of Chengde, Qinhuangdao and Nangong. The sunshine hours had a clear decrease trends. [Conclusion] The research provided scientific basis for realizing regional sustainable development, improving ecological environment and people’s life quality.

Variability and Variation Characteristics of Climate in Northern Winter Wheat Zone during 1961-2004

[Objective] The research aimed to study the variability and variation characteristics of climate in northern winter wheat zone during 1961-2004.[Method] Based on the meteorological data (temperature,precipitation and sunshine) of 55 meteorological stations in northern winter wheat zone during 1961-2004 and the yield data of winter wheat,by using the linear regression,correlated coefficient and climatic tendency rate,the spatial and temporal evolution characteristics of agricultural climatic resources (sunshine hours,temperature and precipitation) in northern winter wheat zone were analyzed.[Result] The annual average temperature,precipitation and sunshine hours in northern winter wheat zone during 1961-2004 all presented certain zonal distribution in the space.The precipitation and temperature gradually decreased from south to north.The sunshine hours gradually increased from south to north.The annual average temperature overall presented rise trend in northern winter wheat zone in 44 years,but the rise rate had difference in the different areas.The rise of annual average temperature in the high-latitude zone was more obvious than that in the low-latitude zone.The annual rainfall overall presented decrease trend,and the tendency rate of annual precipitation had significant difference in the different areas.The decrease rates of rainfalls in the central and western areas were bigger than that in other areas.The annual sunshine hours overall presented decline trend.In most areas,the tendency rate of annual sunshine hours was negative.But there was certain difference in the different areas.The zones where the decrease amplitude was smaller scattered in the west,and included central Shaanxi,south of Shanxi and some areas in southeast of Shandong.The decrease amplitudes were bigger in south of Henan,northwest of Shandong and south of Hebei.[Conclusion] The research provided theoretical basis for understanding the historical evolution of climate in northern winter wheat zone.

Variation Characteristics of Low Temperature and Rainy Weather in Guangxi during Spring Sowing Period of Recent 50 Years

[Objective] The research aimed to study the variation characteristics of low temperature and rainy weather in Guangxi during spring sowing period of recent 50 years.[Method] Based on the daily average temperature data from 1961 to 2010 at 88 meteorological stations in Guangxi,yearly days and end date of low temperature and rainy weather during spring sowing period were carried out statistics.The variation characteristics of low temperature and rainy weather in Guangxi during spring sowing period of recent 50 years were analyzed by using linear tendency calculation,phased analysis,Morlet wavelet analysis and correlation analysis.Moreover,the influences of climate warming on days and end date of low temperature and rainy weather in spring sowing period were analyzed.[Result] The average days of low temperature and rainy weather in Guangxi during spring sowing period from 1961 to 2010 was during 3.5-23.2 d.The regional distribution characteristics were that it was more in northeast and mountain zone,and less in southwest and valley.The regional distribution characteristics of end date were that it was late in northeast and mountain zone,and early in southwest and valley.The days of low temperature and rainy weather in Guangxi during spring sowing period of recent 50 years presented slight decrease trend,and the end date presented slight advancing trend.The phased variation characteristics of days and end date of low temperature and rainy weather were obvious.The days of low temperature and rainy weather from the early 1980s to metaphase of 1990s was obviously more,and the end date was obviously later.After the 1990s,the days of low temperature and rainy weather was obviously less,and the end date was obviously earlier.The days of low temperature and rainy weather had periodic oscillation signals of 4,6,8,10-14 years.The end date had periodic oscillation signals of 6,12-14 years.The days and end date of low temperature and rainy weather in Guangxi during spring sowing period significantly related to average temperature from middle dekad of February to first dekad of April.The climate warming made that the days of low temperature and rainy weather tended to decrease,and the end date tended to advance.[Conclusion] The research provided reference for further understanding the occurrence rule of low temperature and rainy weather,going after profits and avoiding disadvantages,reasonably arranging production,carrying out correlated research.

Variation Characteristics of Sunshine Hours and Its Reason Analysis over Loess Plateau of Shaanxi

[Objective] The research aimed to study variation characteristics of sunshine hours over Loess Plateau of Shaanxi during 1961-2010.[Method] By using the climate tendency rate,climate trend coefficient and linear correlation,the temporal and spatial variation characteristics of sunshine hours in Loess Plateau of Shaanxi in recent 50 years were analyzed.Moreover,the main reason for inducing variation of sunshine hours in the zone was discussed.[Result] In recent 50 years,the variation of annual sunshine hours in Loess Plateau of Shaanxi mainly presented decrease trend.The decrease zones were mainly located in windy desert region along the Great Wall line,central loess hilly region,most areas of plateau remains region and most areas of arid plateau region in north Weihe River.The increase zones were mainly located in west and northeast plateau remains region,southwest plateau remains region,some areas of arid plateau region in north Weihe River.Seen from four-season variation trend,except in spring,the sunshine hours in other seasons presented varying decrease trends.The decrease amplitude in summer was 24.34 h/10 a,and was the most significant.The second one was-16.62 h/10 a in winter.The decrease amplitude in winter was 3.55 h/10 a,and was unobvious.Seen from spatial variation,the annual sunshine hours presented significant increase trend in Mizhi of loess hilly region and significant decrease trend in Dingbian,Shenmu of windy desert region along the Great Wall line,Qingjian,Yanchuan of plateau remains region,Longxian,Fengxiang,Chunhua and Hancheng of arid plateau region in north Weihe River.There was no obvious variation trend in other research zones.The annual and four-season sunshine hours all presented negative correlations with rainfall,relative humidity,total cloud amount,low cloud amount,water vapor pressure and fog days.The sunshine hours presented positive correlation with visibility.The correlation coefficients between sunshine hours and relative humidity,rainfall,total cloud amount,water vapor pressure,fog days and visibility were all bigger in each region.[Conclusion] The research provided basis for analyzing climate variation over Loess Plateau of Shaanxi.

INTERANNUAL VARIATION CHARACTERISTICS OF EAST HEMISPHERIC CROSS-EQUATORIAL FLOW AND ITS CONCURRENT RELATIONSHIPS WITH TEMPERATURE AND RAINFALL IN CHINA

The NCEP/NCAR global reanalysis data were used to analyze the interannual variation characteristics of the cross-equatorial flow (CEF) and its concurrent relationships with temperature and rainfall in China. The results indicated that CEF changes more in summer than in winter. As the main flow channel in summer, the Somali CEF changes in a way that does not markedly influence the changes in the CEF total except for winter. The summer CEF total has two sudden increases and one sudden decrease during the last century while the winter total has just one decrease. Long-period data show that the correlation between CEF and summer rainfall in China is not very significant, but is different before and after the 1970s, which is due to CEF's close links with the East Asia summer monsoon. Winter CEF's correlation with concurrent winter temperature in northern and southern China varies with the relationship between CEF and sea-level pressure in different areas.