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Spatial pattern and characteristics of land cover change in Xinjiang since past 40 years of the economic reform and opening up
CHEN Xi, CHANG Cun, BAO An-ming, WU Shi-xin, LUO Ge-ping
2020, 43 (1): 1-11.   DOI: 10.12118/j.issn.1000-6060.2020.01.01
Abstract268)      PDF(pc) (3211KB)(268)       Save
Since the economic reform and opening up 40 years ago, land use and land cover of Xinjiang, China have undergone tremendous changes. While generating great socio-economic benefits, many ecological and environmental issues have also arisen. In order to provide a basis for future Xinjiangs land use, water resources development, and socioeconomic sustainable development of land and space planning, a partitioned and layered decision tree method and a vector similarity change detection method were used to complete the Xinjiang Land Cover 1100 000 vector dataset in 2015,2010,2000,1990,and 1975 in this paper. The evolution of Xinjiangs land cover change over the past 40 years (reform and opening up of China) was analyzed.From the four stages of reclamation (19751990), agricultural resource development (19902000),western development (20002010), and counterpart assistance to Xinjiang (20102015),the paper described the impact mechanism of national policy on land cover changes. The analysis showed that the land cover change in Xinjiang has begun to transform from a highspeed development model to a sustainable development combined the construction of ecological civilization. The changes of major land types have also shifted from rapid development to basic controllability. In the past 40 years, the area of cultivated land in Xinjiang increased by 128% (50 414.02 km2).The new cultivated land was distributed to the characteristics of water and land resources distribution. The area of artificial surfaces (construction, transportation, industrial, mining land) increased by 197% (7 497.11 km2).The growth rate was obvious accelerated after 2000, and the increase rate in southern Xinjiang after 2010 was very large; the area of forest land before 1990 showed a decreasing trend, and it showed an increasing trend after 1990.The newly added forest land was widely distributed in the natural forest enclosure and within the implementation area of Xinjiang Natural Forest Protection Project. The area of wetlands decreased significantly before 1990, remained stable from 1990 to 2000, and showed an increasing trend after 2000.The area of grassland and other types continued to decrease.
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Variation characteristics of haze weather and its climatic causes in Shaanxi Province
HU Lin, ZHANG Xia, SU Jing, WANG Qi, HU Shulan
2019, 42 (4): 707-714.   DOI: 10.12118/j.issn.1000-6060.2019.04.01
Abstract208)      PDF(pc) (1944KB)(215)       Save
Based on the monitoring data of air pollution in Xi’an City,Shaanxi Province,China,from 2015 to 2016,this paper analyzed the corresponding relationship between haze occurrence and the visibility and quality grade of the air by reconstructing the haze sequences with three different methods,namely,the daily value method,the hourly value method and the value at 14:00 PM method.This analysis helped to determine the value at 14:00 PM method as the method to reconstruct haze sequence and the reconstructing of the historical haze data series was done by using the data about the relative humidity and air visibility from 96 meteorological stations from 1981 to 2016 in order to provide a more reasonable basic data sequence for the environmental meteorological assessment.And then this paper analyzed the characteristics of haze weather and meteorological factors,discussed the circulation situation corresponding to the largescale continuous haze weather process in time and space,and studied the causes of haze weather process in order to provide scientific basis for governmental decisionmaking departments to protect the environment and formulate relevant policies.The results showed as follows: (1) The haze weather occurred frequently in Guanzhong area,followed by Hanzhong Basin in southern Shaanxi,and least in northern Shaanxi.The number of days with haze weather in the province showed a general upward trend,and was increased significantly after 2000.In the province as a whole and in every region of the province,it had the maximal number of days with haze weather in winter.The number of days with haze weather from November to the February next year accounted for 57.9% of the total annual days with haze weather. (2) The frequency of moderate haze (visibility: 5~8 km) and light haze (visibility: 8~10 km) was the highest in the province and all regions of the province,and the frequency of severe haze (visibility<3 km) was the lowest being less than 10%. (3) Wind is one of the important factors affecting haze weather.Haze weather is easy to occur under winter light wind condition.When Xi’an and Guanzhong area are under the effect of northeaster wind,there will be a high frequency of haze weather.(4) The relative humidity is another major factor causing haze weather,the highest frequency of haze weather occurrence was found with the relative humidity being 60%~70%,accounting for about 20% of haze weather occurrences,and the frequency of haze weather occurrence was lower when the relative humidity was less than 30%. (5) The largescale circulation situation in winter was relatively stable.The wind speed was small in Guanzhong area,and there were thermal inversion layers in the near surface atmosphere and wind convergence near Guanzhong area,which caused the horizontal and vertical diffusivity of the atmosphere over Guanzhong to become weaker.When the relative humidity was high,the atmospheric pollutants were accumulated and took chemical reaction.Under these conditions,it is easy to form continuous haze weather and cause serious air pollution in Guanzhong area.
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Climatic variation characteristics in Bayinbuluk during the past 58 years
LIU Mengmeng, LONG Yonglan
2019, 42 (4): 715-723.   DOI: 10.12118/j.issn.1000-6060.2019.04.02
Abstract194)      PDF(pc) (3794KB)(159)       Save
Temperature and precipitation are the most basic meteorological elements.Recently,the northwest China is very sensitive to the climate change.Bayinbuluk grassland in Hejing County,Xinjiang,China has a unique alpine climate with a more pronounced response to climate change.Therefore,more and more meteorologists are attracted to study the trends of local temperature and precipitation.By using EEMD,the characteristics of precipitation,precipitation days and annual average temperature were analyzed based on longterm (from 1958 to 2015) monthly average temperature and monthly precipitation data from Bayinbuluk Meteorological Station.The MannKendall and cumulative anomaly analysis methods were used to diagnose the mutation points.Meanwhile,based on Morlet wavelet analysis method and R/S analysis method,the periodic characteristics and long memory property were analyzed.It is found that the monthly precipitation in Bayinbuluk was increased significantly in January,June and November,and the changes in February,July and December displayed a “convex” shape.The monthly precipitation days showed a significant downward trend in January and September,with a significant increase in February and June,and a “convex” change in March and November,a “concave” change shape in May,July and August.The average temperature in each month was basically on rise,especially in May,July and October.There were big changes for the annual precipitation and annual precipitation days in 1999 and 1993,and big change for the annual mean air temperature occurred in 1997.In addition,the increase of the annual precipitation days happened earlier than the increase of the annual precipitation and the increase of the annual average temperature.Since the mid1990s,Bayinbuluk’s climate has shifted from dry and cold to warm and humid.The periodic oscillation of annual precipitation,annual precipitation days and annual average temperature were 41 a,9 a and 30 a,respectively.Meanwhile,the Hurst exponents were obtained,which indicated that in the future annual precipitation and annual average temperature would be increased but annual precipitation days would be decreased.The frequency of extreme precipitation will be increased,which will easily lead to flood disasters.
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Formation mechanism of a southeast gale event in Urumqi urban area: The coupling of gravity wave and ultra-low level jet
TANG Hao, WANG Xu, CHU Chang-jiang, SUN Ming-jing
2019, 42 (6): 1229-1238.   DOI: 10.12118/j.issn.1000-6060.2019.06.01
Abstract152)      PDF(pc) (4663KB)(100)       Save
There is a northwest-southeast-oriented canyon in the middle of the Tianshan Mountains, Xinjiang, China, the length of the canyon is about 80 km, the altitude at the bottom of the valley is about 1 200 m, and the height of the mountains is about 3 000 m. Urumqi is located in the northwest opening downhill of the canyon, the Turpan Basin is located at the southeast opening. This paper uses the mesoscale WRF model to simulate the strongest southeastern gale in the past 10 years in Urumqi City which occurred on March 30, 2012.The simulated output of high temporal-spatial resolution is analyzed. With the simulation and the diagnostic analysis we concluded that the southeast gale in Urumqi is a strong downslope windstorm triggered by the combination of gravity wave and ultra-low level jet which was caused by the special landform in Tianshan canyon. The formation mechanism is summarized as follows: (1) The cold air at the bottom of the Mongolian high pressure flows back into the basin from the eastern part of the Tarim Basin, accumulates and forms a ground high pressure on the south side of the Tianshan Mountains. On the north side of the Tianshan Mountains, the front decompression occurs due to the intrusion of cold front, and thus pressure field on both sides of the Tianshan Mountains is high in the South and low in the North. Under the action of the pressure-gradient force, the cold air enters the Tianshan Gorge, and the airflow gradually accelerates due to the funneling effects. In the middle of the canyon, the wind is southeast and the wind speed exceeds 8 at a distance of 300 meters from the ground. (2) During the process of cold air at the southern end of the canyon climbing into the canyon, gravity waves are formed by the forced lifting due to the terrain. As the pressure gradient on both sides of the canyon increases, the amplitude of the gravity wave increases and is coupled with the ultra-low-level jet, the gravity wave forms a leeward wave hydraulic jump at the northern end of the canyon, triggering a strong downhill storm on the ground, that is the southeast gale in Urumqi. (3) There are two factors complementing each other and thus enhancing the ultra-low-level jet energy. One of them is the critical layer of the shear of southeast and southwest winds above the ultra-low-level jet stream absorbs the upper-layer wave energy and transmits it downward to the ultra-low-level jet stream; the other is the gravity wave breaking turbulence exacerbates the downward transfer of energy in the rapids. In this process, the stable atmospheric stratification of the lower troposphere over the leeward slope exacerbates the sinking motion of lee wave and the energy transmission caused by it.
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Characteristics of air temperature inversion and relative humidity inversion between the near ground surface in the oasis and the leading edge of shifting sandy land of Cele in the southern margin of Taklimakan Desert
MAO Dong-lei, CAI Fu-yan, LI Xin-guo, LEI Jia-qiang, LAI Feng-bing, XUE Jie
2019, 42 (5): 976-985.   DOI: 10.12118/j.issn.1000-6060.2019.05.02
Abstract144)      PDF(pc) (1874KB)(110)       Save
The study of the characteristics of nearsurface inverse temperature and inverse humidity between the quicksand front and the oasis provides a basis for the transfer of heat and vapor between the desert and its inner oasis. Utilizing the method of synchronous contrast and statistical analysis, this paper investigated the characteristics of inverse temperature and inverse humidity between the height of 0.5 m and 2 m near the ground surface between the quicksand frontier and the inner oasis of Cele County, Xinjiang, China based on the field observation data. The results show that the average monthly relative humidity in the quicksand frontier hit the maximum value in October, and the minimum in April. The highest temperature appeared in August and the lowest in January. In July 2011, the intensity of inverse temperature and humidity was the highest, and the number of inverse humidity days in this month was accounted for 38.71% of the total inverse humidity days. The number of inverse temperature days was accounted for 3.76% of the total temperature inversion days. The temperature inversion time was between 19:00 PM and 10:00 AM next morning, the inverse humidity appeared between 10:00 AM. and 21:00 PM. From the month perspective, the lowest temperature in the oasis occurred in January 2011,the highest in July 2011.The minimum relative humidity occurred in April 2011.The maximum relative humidity appeared in September 2010 with the value being 74.91%.The strongest inverse temperature and inverse humidity appeared in November 2010,with an average daily temperature difference of 3.48℃ and a high humidity difference of 2.27%.In general, between the leading edge of the quicksand and the inner oasis, the relative humidity in winter is greater than the relative humidity in summer, while the temperature is high in summer and low in winter. The air temperature and humidity at the same height showed a good negative correlation. In the four typical weather conditions, the temperature and humidity changes shared the same pattern as the change characteristics of the inverse temperature and inverse humidity between the quicksand frontier and the inner oasis, but the changes happened first in the oasis followed by the shifting sandy land. However, in the conditions of cloudy weather and blowing sand weather, the inverse humidity happened first in the shifting sandy land followed by the inner oasis, and the last time for inverse temperature and inverse humidity in the oasis is primarily longer than that in shifting sandy land.
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System of three scale multi-objective water cycle regulation theory and engineering technology
DENG Ming-jiang
2019, 42 (5): 961-975.  
Abstract131)      PDF(pc) (4178KB)(126)       Save
Taking typical inland river basins in arid region of Xinjiang, China as a research subject, the paper shows three major existing problems of development and utilization of water resources, which are water resources shortage with serious spacetime imbalance distribution & noticeable problem of water safety of trans-boundary rivers, overdevelopment of water resources & serious structure imbalance between artificial and natural oases & ecological environment deterioration, low efficient utilization of water resources & imbalance of water and salt & contradiction between supply and demand of water resources on systematical analysis of local geography, landform, hydro-meteorological information and characteristics for water cycle of river basins. It establishes three-scale (macro-, meso-, micro-scopic scale) multi-objective water cycle regulation theory and engineering technology system and provides scientific model and key technology of water cycle regulation for regions, basins and irrigation zones & high efficient utilization of water resources, leading by water problem and its requirement & simultaneous development of engineering measures and ecological protection and adopting systematic scientific basis theory and analysis method. Combing region landform and geographic characteristics with water resources condition, it builds up water cycle regulation structure, which is net type for north Xinjiang, ring type for south Xinjiang, and cluster type for east Xinjiang in order to strengthen regulation capacity of reasonable allocation of regional water resources. Aiming at characteristics of water cycle of basin, it proposes comprehensive regulation model of plain reservoirs replaced by reservoirs in mountainous area, Three-seven Regulation between inland and outland waterway, Five-five Control for ecological and economical water uses. Surrounding current construction of irrigation zones and its challenge, it sets up Four-in-one (water-saving irrigation & regulation of water and salt & groundwater use & ecological protection) comprehensive regulation technology system for high efficient water resources use, which is the development direction of sustainable oasis agriculture in arid region.
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Changes of precipitation area in China from 1961 to 2015
2019, 42 (4): 762-773.   DOI: 10.12118/j.issn.1000-6060.2019.04.07
Abstract129)      PDF(pc) (3487KB)(108)       Save
The nonuniformity of precipitation elements (precipitation, precipitation intensity,precipitation frequency,precipitation area) in time and space leads to the frequent occurrence of many natural disasters (storms,floods,continuous rain,landslides,mudslides,et al.),causing great losses to people’s production and life,which have raised great concern. Based on 0.5°×0.5° monthly and daily precipitation grid datasets in China from 1961 to 2015,the characteristics of precipitation and precipitation area in three regions of China were analyzed using linear trend method,Kriging interpolation method and forest slope method.The annual and seasonal average precipitation both presented a decreasing pattern from the southeast coast to the northwest inland,the annual and seasonal average precipitation in over half of China’s region showed an increasing trend.In terms of daily and seasonal variations,light rain and moderate rain mainly were concentrated in the eastern monsoon region and the northwest arid region and the QinghaiTibet alpine region of China,but the area occupied by rainstorm and heavy rainstorm was small.The annual variation of daily precipitation area at different levels in the three regions followed a quadratic function curve,and the inter annual variation of the average precipitation area in the three regions showed a slight decrease.The heavy rain,rainstorm and downpour displayed a slightly increasing trend in the QinghaiTibet alpine region and the arid areas of northwest China.From the seasonal change characteristic perspective,the light rain dominated in all seasons in the three regions.The areas with rainstorm or downpour accounted for a smaller proportion.Precipitation areas of light rain in the three regions in spring and autumn showed a decreasing trend,and rainstorm in spring and summer showed an increasing trend,and moderate rain and heavy rain in winter showed an increasing trend.The precipitation areas at different levels of precipitation all conformed to a negative index distribution in the eastern monsoon region in spring and autumn,in the arid areas of northwest China in all seasons and in the QinghaiTibet alpine region in spring,autumn and winter.The variation characteristics of precipitation area in China provides a good basis for formulating climate change strategies.It is also of great significance for the comprehensive management of water resources and flood control and disaster mitigation in the basin.
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Causal analysis of MCS in a short time severe precipitation process  under the background of Central Asia vortex
LI Jiangang, JIANG Cailian, ZHANG Yunhui, LI Ruqi, YANG Lianmei
2019, 42 (4): 724-734.   DOI: 10.12118/j.issn.1000-6060.2019.04.03
Abstract121)      PDF(pc) (3423KB)(79)       Save
In order to understand the triggering and developing mechanism of Mesoscale Convective System (MCS) in the Tianshan Mountains,the causes of MCS in a short-time severe precipitation process under the background of Central Asian vortex in the Ili Valley of Xinjiang,China were analyzed deeply.Based on the hourly precipitation data,the temporal spatial distribution characteristics of the precipitation were obtained.The cloud pattern and radar characteristics of MCS were analyzed according to FY-2G satellite TBB products and Doppler weather radar data.The results indicated that MβCS in this area had obvious characteristics of nocturnal and backward propagation,being formed over the mountain areas and developed,enhanced and retained for a long time period over the plain areas.The continuous occurrence of strong echo zone,adverse wind region and ultralow level jet on the radar map illustrated the enhancement of local convection.Moreover,the rainfall intensity of representative stations was analyzed with corresponding TBB and radar echo,which showed that the spatial and temporal distribution of rainfall intensity was proportional to the TBB gradient,ET and VIL respectively.Using sounding,surface wind field and ERA-Interim reanalysis data,the largescale circulation background and mesoscale characteristics of MCS was analyzed,which concluded that enhanced local convective activity triggered the formation of MCS in the front of deep Central Asian vortex,and the multi-channel water vapor transport and long-time water vapor convergence in the middle and low levels,the atmospheric instability stratification,and convergence and vertical shear of wind field in the low and middle levels,the increase of θse between the upper and lower level and the enhancement of warm advection in the lower level provided better dynamic,thermal conditions and water vapor for the development and retainment of MCS.
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Spatiotemporal variation characteristics of surface evapotranspiration anddrought at the oasis area of the southern Xinjiang in recent 14 years
GAO Yulian, LIU Jinbao, LIU Weiyang, YU Jing, LIU Zhihong
2019, 42 (4): 830-837.   DOI: 10.12118/j.issn.1000-6060.2019.04.14
Abstract120)      PDF(pc) (2947KB)(93)       Save
Evapotranspiration is estimated based on NDVI,surface net radiation,air temperature by using China monthly meteorological data and MODIS remote sensing data which include evapotranspiration data(MOD16) and normalized difference vegetation index data(MOD13).Simplify and improve the parameters of mixed linear dual source remote sensing evapotranspiration model to estimate the surface evapotranspiration in oasis region of southern Xinjiang,China.Analysis of spatial and temporal variation characteristics of the actual-evapotranspiration (ET) and potentialevapotranspiration(PET) from 2001 to 2014.Besides,based on the correlation analysis of measured evaporation data from meteorological stations in southern Xinjiang,the applicability of MOD16 products in oasis region is already credible by means of statistical test.According to the evapotranspiration drought index (EDI),the distribution characteristics of drought in oasis of southern Xinjiang is analyzed,and the degree of drought is determined by the EDI anomaly.The results reflect that the annual mean evapotranspiration from 2001 to 2014 shows little change,and these are significant difference among the four seasons.The highest evapotranspiration is in summer and the lowest in winter.The spatial trend of ET and PET is in opposite situation.In addition,there is a huge disparity between the annual value of ET and PET which means the surface water shortage is serious in oasis.Furthermore,the average annual value of EDI index in oasis area is fairly large,the response of EDI anomaly to drought and the judgment of drought degree are reliable.From the perspective of energy and waterbalance,this research simplifies the model parameters and enhances the applicability of the model.It has certain guiding significance for large scale areas evapotranspiration estimation and drought monitoring.
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Soil erosion and geographical environment in dry valley of the middle reaches of Bailong River
WEI Hong-qing, SHEN Yong-ping, WEI Li-hui, ZHANG Feng
2019, 42 (5): 1023-1028.   DOI: 10.12118/j.issn.1000-6060.2019.05.07
Abstract117)      PDF(pc) (2459KB)(99)       Save
The geological structure in the middle reaches of Bailong River in Gansu and Sichuan Province,China is composed of a series of east-west folds and faults,and the formation lithology is exposed from Silurian to Quaternary.The soft rocks and hard rocks are interlayer or interbedded superimostion,and the dry valleys have obvious climatic characteristics,which is the most active geological unit of landslides.Soil and water erosion in this area has reached extremely serious viscous debris flow property,and the spatial distribution is related to geological,geomorphic,climatic and human activity factors,showing vertical zonal differentiation characteristics.Most debris flow channels are formed gully with small drainage area and “scoop” shape.The geomorphologic process is orderly in space,forming a process of precipitation convergence—water and soil mixed-transport and soil erosion.Taking the small watershed of Ganjiagou as an example,using the orderly characteristics of spatial structure,the combination of arbor and shrubs is adopted in the precipitation gathering area to create 1 300 hm2 of soil and water conservation forest and grass,which effectively intercepts precipitation.In the unfavorable geological action areas such as landslide collapse,16 km of drainage ditch is arranged to take the surface water out of the landslide area; sloping farmland builds 580 hm2 of horizontal terraces to reduce runoff on the slope.Erosion gully layout of 25 masonry stone lanes,interception of sand and stones,the stability of the gully bed,fixed slope.Thirteen sand barriers were built in the transport area to raise the erosion standard in sections,reduce the gully bed ratio and destroy the groove boundary conditions.The dam body drainage and water sand separation were used to make the channel gradually silt,disperse fluid along the capacity.Drainage ditches will be set up in the accumulation areas to set aside super-standard flood channels,protect downstream villages,farmland and important infrastructure,fully configure the prevention and control system of water and soil conservation,and realize the comprehensive control of mountains,rivers,fields and forests.After years of observation and follow-up investigation,no debris flow disaster has occurred in the basin since the treatment was completed in 1998.Practice has proved the comprehensive management mode of small watershed of Ganjiagou use soil and water conservation ecological measures to change the mountain micro-geomorphology structure,artificially intervenes to transform the channel boundary conditions,and combines the treatment of gully and slope,unblocking and blocking,and highlighting the ecological,Which is the effective way of administer landslide and debris flow disasters under currently local economic and technological conditions,and provides an effective reference for establishing comprehensive management models in similar areas.
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Desertified land change and its causes in Co Nag Lake region along QinghaiTibet Railway
CHEN Changwei, WU Yongqiu, TAN Lihua, DU Shisong, DUAN Jinlong
2019, 42 (4): 885-892.   DOI: 10.12118/j.issn.1000-6060.2019.04.20
Abstract111)      PDF(pc) (1352KB)(78)       Save
The impacts of desertified land change (DLC) during the construction of QinghaiTibet Railway of China from Golmud to Lhasa have given rise to important research significance.Based on the Landsat image,Google Earth image and the meteorological data about Co Nag Lake region along QinghaiTibet Railway,this study uses RS and GIS technologies and conducts fieldwork to establish interpretation signs and to construct a classification & grading system for the DLC in the study area,and then employs visual interpretation method to extract the DLC information in 2001,2008 and 2015 respectively.The spatiotemporal evolution of the DLC over the last 15 years is analyzed.The results show as follows: (1) In 2015,the desertified land was mainly sandy land but the area of sandy gravel land was relatively small in study area.The area of desertified land was increased by 2.21 km2 from 2001 to 2008 yet the degree of land desertification showed a declining trend.The desertified land was decreased by 8.9 km2 from 2008 to 2015 and the declining degree of land desertification continued. (2) From 2001 to 2008,the increase in desertified land area was related to the increase in the number of livestock such as yak and sheep.The decline of land desertification was mainly due to the increase of annual mean temperature and the decrease in annual mean wind speed.From 2008 to 2015,the decrease of desertified land and the alleviation of the degree of land desertification were resulted from the gradual decrease in the number of livestock and the implementation of ecological restoration projects by the local government.Hence,human activities played an important role in the decline of land desertification in the 15 years. (3) The construction of the Qinghai-Tibet railway generated a disturbance to the ecological environment in the study area.The scope of influence by railway is about 2 km.While the engineering measurements of controlling land desertification along the railway lines played an important role in alleviating the degree of land desertification.In short,the discussion of the factors including the impacts of railway construction on DLC can provide some scientific basis for the prevention of land desertification and for the rehabilitation of ecological environment.
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Urban recreation space pattern based on POI data:A case of Urumqi City
JIA Xiaoting, LEI Jun, WU Rongwei, WANG BOli
2019, 42 (4): 943-952.   DOI: 10.12118/j.issn.1000-6060.2019.04.26
Abstract111)      PDF(pc) (3481KB)(74)       Save
Urban recreation space is an important organic part of a city,and its development is a reflection of not only the urban socioeconomic culture,but also the evolution of urban spatial structure.Based on Baidu POI data,using Ripley’s K function,spatial autocorrelation,and the nearest neighbor hierarchical clustering analysis methods,this paper studied the spatial characteristics of public recreational facilities in Urumqi City,Xinjiang,China,summarized the patterns of urban recreation space,and explored the influencing factors of urban recreation space.The results show as follows: (1) The spatial distribution of the leisure facilities in Urumqi shows a marked centrality and agglomeration. (2) The hot spots of the six kinds of recreational facilities show different tendency of agglomeration.The entertainment facilities,shopping facilities and sport facilities tend to cluster near important transport hubs and commercial centers.The hotspots of catering facilities show obvious population orientation.The hot spots of tourism facilities are all located near hot scenic spots.The hot spots of cultural facilities are located in the mixed ethnic areas. (3) The recreation space pattern in Urumqi is displaying a “layer+ sector + group” mode.The city center is the planar comprehensive leisure center,and the periphery of the city center is the fanshaped leisure facilities area with low density,grouped multifunctional leisure area and grouped catering leisure area.The suburbs have few leisure facilities but are grouped tourism leisure areas. (4) It is proved that the recreation space of Urumqi is positively correlated with the spatial distribution of population.
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Cropping structure extraction with [WTHX]NDVI[WTHZ] timeseries images in the northern Tianshan Economic Belt
XIONG Yuan-kang, ZHANG Qing-ling
2019, 42 (5): 1105-1114.   DOI: 10.12118/j.issn.1000-6060.2019.05.16
Abstract111)      PDF(pc) (2570KB)(110)       Save
 

Limited water resources is the major factor affecting sustainable development in arid areas,and the water resources in arid areas are mostly used for agricultural irrigation.Rapidly and accurately mapping cropping structure in arid areas can provide an important basis for optimizing water use in agriculture.In this study,the Northern Tianshan Economic Belt,Xinjiang,China was chosen as the study area,and a method to map the cropping structure in this region with multi-source remote sensing data based on the Google Earth Engine (GEE) cloud platform was proposed.The Sentinel-2 and Landsat 7-8 data were chosen as the remote sensing data sources to extract the cropping structure in the study area through the following steps. First, in order to simplify the cropping structure extraction process and minimize the impacts from non-crop vegetation, a cropland mask was constructed by using the maximum NDVI value and slope information throughout the year in the study area.Second,according to the phenology calendars of the main crops in the study area, the time-series data of the maximum NDVI value and the corresponding date was calculated with remote sensing data. Then, the 10 feature bands were constructed. Third, the 10 feature bands were masked with the cropland mask. Based on these data together with the field samples, the random forest classifier was applied to cropping structure extraction. The accuracy evaluation results showed the overall accuracy of the classification results in 2018 was 92.19%,and the Kappa coefficient was 0.883.In order to further verify the accuracy of the classification algorithm, the crop structure in the study area in 2017 was also extracted, the classification results showed that the planted area of cotton, corn and wheat in the study area were 5 270 km2,2 000 km2 and 2 340 km2 respectively in 2017, and then compared it with the results of statistical yearbook data in 2017.The relative accuracy of cotton, corn and wheat planted area were 86.53%,77.54% and 86.19%,respectively.

 

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Extraction of crop planting structure based on timeseries NDVI  of Landsat8 images
BAI Yanying, GAO Julin, ZHANG Baolin
2019, 42 (4): 893-901.   DOI: 10.12118/j.issn.1000-6060.2019.04.21
Abstract109)      PDF(pc) (4095KB)(70)       Save
In order to improve the accuracy and efficiency of remote sensing monitoring of crop planting information in plain irrigation area in Inner Mongolia,China,this paper proposes a method of crop planting information extraction based on timeseries NDVI profile.Selecting Tumoteyou County of Inner Mongolia as the study area,using the multitemporal Landsat images covering crop growing season in 2015 as data sources,the study area was divided into vegetation covering area,nonvegetation covering area and water covering area according to the NDVI value range of ground objects.In the area of vegetation covering,the forest area and grass area were extracted successively according to the NDVI curve differences of forest and grass.The rest areas were farmland in vegetation covering area.According to the NDVI profile of wheat,corn,sunflower and zucchini,the decisiontree was built,and the spatial planting information of the crops was extracted successively according to the decisiontree.Building the decisiontree is mainly based on the difference of NDVI average curve characteristics between crops,forest and grass.However,the change range of each crop NDVI due to their own different growth at the same time should also be fully considered.Appling the decisiontree,the extraction area of land use and crop is close to the actual statistical area.The overall accuracy of land use classification was 85.71% and the Kappa coefficient is 0.75.The overall accuracy of crop classification was 82.69% and the Kappa coefficient was 0.77.The results show that the research method can monitor crop spatial planting information in the region accurately and effectively.
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Dry and wet environment evolution and climatic background analysis of regional ecological construction in Inner Mongolia
DAI Haiyan, LI Dan, NA Risu, CHEN Suhua, DU Wala
2019, 42 (4): 745-752.   DOI: 10.12118/j.issn.1000-6060.2019.04.05
Abstract102)      PDF(pc) (3207KB)(63)       Save
The temperature in Inner Mongolia,China keeps increasing from 1971 to 2016.According to the result of MK mutation test,there was a sudden change of the annual average temperature in 1988.The temporal and spatial variation characteristics about the dry and wet environment of the main vegetation types in the region was derived based on the analysis of the change and the tendency rate of the precipitation,potential evapotranspiration and moisture index before and after the sudden change of the air temperature in the course of the late 46 years.The results showed that the precipitation had the pattern of an increasing trend in the east area but a decreasing trend in the west area before the sudden change of the temperature,and it turned to an opposite pattern after the sudden change of the temperature which meant a decrease trend in the east area but an increase trend in the west area.The areas with a precipitation trend rate in the past 46 years were mainly concentrated in the east of Hulun Buir League and most area of the western Ulanqab League.The evapotranspiration showed a decreasing trend before the sudden change of the temperature,but an increase trend after that change,and the latent evapotranspiration was significantly smaller after the sudden change of the temperature.The potential evaporation tendency was relatively small in most areas in the past 46 years with the exception only in the northcentral part of Inner Mongolia.There was an obvious “evaporation paradox” in most parts of the region.The desert,steppe desert and desert steppe in the west region of Inner Mongolia were in the humid climate background,which was beneficial to the local vegetation construction and ecological recover.In southeastern Inner Mongolia,and the grasslands of Hulun Buir and Xilingol League there was a warming and drying tendency,which poses a potential degradation risk in the above steppe areas.It is required to strengthen the maintenance of natural fending and ecological stability of the grassland areas,to reduce human disturbance,and largescale artificial vegetation construction should be prohibited at present.The conclusion can provide scientific basis for regional ecological construction,vegetation protection,reasonable utilization of regional climate resources and climate change solutions.
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Jobbinghousing relationship in central urban area ofYinchuan City based on Baidu heat map
WANG Lucang, CHANG Fie
2019, 42 (4): 923-932.   DOI: 10.12118/j.issn.1000-6060.2019.04.24
Abstract99)      PDF(pc) (2545KB)(78)       Save
“Job” and “Housing” are the most basic functions of the city,and the relationship between job and housing reflects the order and efficiency of the city.Under the planned economic system of China,under the profound influence of “unit(Danwei) management society”,the relationship between work place and residence was very well matched.After 1992,with the drastic transformation of urban economy and society in China,the situation of separation between work place and residence has become increasingly prominent,which has led to a series of housing,commuting,social equity and other issues.Based on the realtime dynamic big data provided by Baidu Heat Map,Baidu Road Map and the urban landuse map,this paper analyzes the relationship between job and housing in the main urban area of Yinchuan City,Ningxia Province,China.The whole day is divided into five periods (two commuting periods,two working periods and one rest period).The Baidu Heat Map in different periods and for different land use are obtained to depict the population aggregation situation in the main urban area.The results showed that:During the working day,the proportion of the highheat zones was increased significantly from 7:49 AM,especially in the period from 7:49 AM to 9:11 AM,which was closely related to the peak commutes,and then fluctuated upwards,but was basically stable from 9:11 AM to 18:15 PM,which was consistent with the normal working hours.Starting from 18:15 PM,it was dropped sharply,which was commensurate with commuting peak.After 19:38 PM,it started to go up again,and this was a rest period.During the working hours,the population concentration on the educational and commercial lands was stronger,while during the rest period,the population concentration on the residential land is more obvious.Baidu Heat declined when a large number of people left the residential area during the working hours,and rose when they returned to the residential area during the offduty hours,which means that there is a rhythmic pendulum flow between residential areas in the workplace.Residents in the working hours are highly concentrated in business centers,urban complexes,universities,hospitals and logistics centers,etc.During the rest period,the high concentration centers of the population changed from employment centers to residential areas and leisure shopping areas,indicating that there is a certain separation of work and residential areas in the main urban area.According to the ratio of occupation and housing,the relationship between employment and housing is divided into five types: basic balance type,slight employment tendency,serious employment tendency,slight inhabitation tendency and serious residence tendency.Generally speaking,the balance of job and housing in urban central area is more obvious than that in the outlying areas,and there are great differences between functional groups.The south group of Xixia District is an industrial concentrated distribution area,the north is a university concentrated distribution area,so there was a basic balance of residential and employment; the south group of Jinfeng District and the east group of Xingqing District exist a large number of commercial residential areas where living is significantly higher than employment; the northwest group of Xingqing District is the commercial and trade center and so is the old urban area of Yinchuan City,where the employment is more prominent.
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Change of above ground net primary productivity of grassland over the Mongolian Plateau in recent 56 years
QIN Haojun, HAN Yongxiang
2019, 42 (4): 914-922.   DOI: 10.12118/j.issn.1000-6060.2019.04.23
Abstract97)      PDF(pc) (3398KB)(79)       Save
Study of the grassland productivity and its response to the climate change has been an important aspect of the global change research.By using the ArcGIS interpolation technique,the observed data from 32 meteorological stations in the Mongolian Plateau are interpolated into the 1°×1° grid data,and then the spatiotemporal distribution characteristics of the above ground net primary productivity (ANPP) of the vegetation over the Mongolian Plateau from 1961 to 2016 are simulated by the CENTURY model.The results are shown as follows:(1) The spatial and temporal distribution of the ANPP simulated by the CENTURY model can well reflect the change of the grassland productivity in the Mongolian prairie,and the distribution of the ANPP in grasslands changed from north to south gradually from east to west.(2) The yields of meadow steppe and typical steppe are decreasing over time and the decrease rate of meadow steppe is higher,and the yields of desert steppe is rising over time.The largest total yields are in the typical steppe,and the lowest total yields are in the desert steppe which has the largest area.(3)The precipitation is the key factor for the grassland productivity.In the wetperiod,there exists the transformation of desert steppe→typical steppe→meadow steppe,while the process of dryperiod conversion is the opposite.The total yields of Mongolian steppe have the largest decrease when it is changed from the warmwet period to the drycold period. In contrast,the total yields have the largest increase when it changed from drycold to warmwet.
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Spatial and temporal distribution characteristics of sand drift potential in Taklimakan Desert
SUN Xiao-yun, FANG Yan-jie, ZHAO Jing-feng, HE Qing, ZHOU Jie
2020, 43 (1): 38-47.   DOI: 10.12118/j.issn.1000-6060.2020.01.05
Abstract96)      PDF(pc) (2982KB)(110)       Save
Taklimakan Desert is the largest sand desert in China, which is located in the Tarim Basin, Xinjiang. The rates of sand transport by wind plays the most important role in its aeolian surface processes. The Fryberger Method provides a useful and accessible way of evaluating the relative rates of sand transport (drift potential, DP) from measurements of wind data. With this method, a number of different estimations of DP about Taklimakan Desert have been proposed for the past decades. In this paper, we recalculated the DPs using the definition equation in which the arguments are the every measurements of wind velocity rather than the calculation model in which the arguments replaced by the midpoint of each velocity category, in order to clarify the cognition of the wind-energy environments in the sand sea. The calculations in the paper shows that the DP values of 22 meteorological stations ranged from 0.7 VU to 33.4 VU in 2007thus the wind regimes should be classified into the Low-energy wind environments by using of the Fryberger classification.Based on the analysis of resultant drift potential (RDP),involving the RDP similarity (Cluster Analysis of Inner Product Similarity) and the region adjacency of a RDP type, the RDPs have been classified into five typesnamely, Korla type in eastern Taklimakan with the RDPs showing W-S directions (abbr. W-S type), Xinhe type in the northern region as S type, Cele type in the western region as E type, Minfeng type in the southern region as E-NE type, and Special type with the RDPs at three stations being obviously different from their adjacent regions. The maximum average DP was caused by the NW wind regime, which happened in Cele type, and the lowest ratio of the directional variability of the winds (RDP/DP) was induced by the NE wind regime, which happened in Korla type. As a contrast,in the convergence zone between the NW and the NE wind regimes, the DPs was relative lower (Xinhe type with the minimum of DP),and the ratio of RDP/DP was higher (Minfeng type with the multi-direction effective winds) than the above two types. The cumulative DP from spring to summer in 2007 had reached to 81.29%-98.79% of the annual DP, only in May it accounted for 22.7% to 56.8% of the annual DP; whereas in winter except for February, almost no effective sand-driving winds had occurred over Taklimakan. In the southeast edge of the desert, under the normal weather condition, the northwest wind system moved eastwards between Qiemo and Ruoqiang County in May however it retreated back to the west of Tazhong region and between Minfeng and Qiemo in February. This indicated that the positions of the wind convergence zone under the strong wind weather were shifted eastwards. During the period from 2005 to 2007,the inter-annual variation of RDP showed as ±33% in magnitude and ±9.6° in direction as a whole; but some specific stations displayed larger variations of the RDPs, such as a variation of ±80% in magnitude at Aral station and a variation of ±24.4° in direction at Kuqa station.
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Temperature variation characteristics of northwest China based on K-means clustering partition in the past half century
FENG Ke-peng, TIAN Jun-cang, SHEN Hui
2019, 42 (6): 1239-1252.   DOI: 10.12118/j.issn.1000-6060.2019.06.02
Abstract95)      PDF(pc) (4123KB)(80)       Save
The northwest region in China is vast, with administrative divisions including parts of Shaanxi, Gansu, Ningxia, Qinghai, Xinjiang, and Inner Mongolia. Arid, semi-arid and semi-humid climates coexist in the region. Mountain, Gobi, oasis, desert and other topographical features are intertwined. The northwest region in China is ecologically fragile and sensitive to climate change. It is well known that climate warming and rising temperatures accelerate the water cycle and add up the intensity and frequency of occurrence of extreme weather events such as high temperature and drought and heavy rains. At the same time, it also leads to the uneven distribution of water resources in time and space, and the complexity and difficulty of dealing with floods and droughts. On the contrary, after the temperature stops rising, the water circulation process will slow down; the water cycle elements such as precipitation, evaporation and runoff in the region will inevitably change, which will affect the industrial and agricultural production and the people s life in the region. In the new context of climate warming mitigation, this paper analyzes and discusses how the temperature in Northwest China has changed. Is there a warming slowdown? How does temperature respond in different seasons? In this study based on the observations of temperature by 184 meteorological stations in the northwestern region, by using K-means clustering partition, Sen s slope estimation and Kendall-Tau nonparametric test methods, the temperature variation characteristics of Northwest China in the past half century (19602015) were analyzed. The results show that the temperature in the northwestern region has been increased significantly in the past half century, and the rise rate of annual average minimum temperature is higher than those of the average annual temperature and the highest annual average temperature. From a spatial point of view, the northeastern part of the northern Xinjiang, the northern, western, central and eastern parts of Inner Mongolia, the central and western parts of Gansu Province, the northern and central parts of Qinghai Province, the central and northern parts of Ningxia Province, and the northwestern part of Shaanxi Province are the fastest warming areas. Although the temperature in the northwestern region is generally on the rise, there is a difference in specific areas. Since 1998, the temperature in the northwest region has been slowed down, and some regions have experienced a downward trend. In the past half century, the seasonal temperature and the interannual temperature in the northwestern region are not consistent, and the warming slows down in different seasons in the region. During the period from 1998 to 2015, winter is the season with the smallest increase in temperature. In most sub-regions, the warming trend in winter has been slowed down and even turned into a downward trend. This paper analyzes the trend of temperature change in the northwestern region in the past half century from different spaces and observes the phenomenon of warming mitigation in the northwest region, and this trend is inconsistent in different sub-regions and different seasons. According to the comparison with related researches, the years of warming stagnation found in this paper are consistent with the relevant research conclusions. At the same time, the conclusions of this paper could enrich the understanding of climate temporal and spatial changes in the region and provide assistance for further understanding the temperature variation law in this region.
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Comparative analysis of weather conditions and Doppler radar characteristics of two hailstorm events in Korla in 2015
PENG Jun, TANG Dazhang, ZHOU Xueying
2019, 42 (4): 753-761.   DOI: 10.12118/j.issn.1000-6060.2019.04.06
Abstract94)      PDF(pc) (4477KB)(73)       Save
By using conventional detection data,Doppler weather radar data,FY2E geostationary satellite and the 0.5°×0.5° reanalysis data provided by NCEP/NCAR,the comparison between two hail weather courses occurred in Korla City,Xinjiang,China in 2015 were analyzed in this paper.The results showed that it was a shallow system with shortwave trough on 17th April 2015 while it was a deep system with vortex circulation on 1st June 2015.Before the occurrence of the hail,there was strong vertical wind shear and the height from the 0 ℃ layer to the -20 ℃ layer was suitable to have a shallow saturated wet layer between them.Due to the humidifying by the rainfall in the southeastern part of the Tarim Basin,water vapor was transported to the area with the cyclonic flow field and raised in front of mountain.The strong convection was triggered by the shear line between the southeast wind and northeast wind over Korla City and Luntai County.From the satellite image,the rapid development of hail clouds near the shear line was also reflected.The hail appeared near the southeast edge of the cold cloud cover with a cloud top temperature less than -50 ℃,where the cloud clusters merged.The hail system mainly moved along the average wind direction in the middle and lower layers.Both the two hail processes,the echo intensity of the center exceeded 55 dBz and the upwind zone occurred along with the development of the hail.The strong echo broke through the -20 ℃ layer and there was a strong echo with the intensity more than 50 dBz between 0 and -20 ℃ layer.The intensity and the time of duration of the hail on 1st June were much more than those on 17th April,especially for the echo overhang and weak echo regions,which was directly related to the strong upwind with long duration.When the center of the strong echo dropped to the lower level and the flow field of the lower layer was divergent,the hail weather tended to end.Under favorable environmental conditions,it was the most prominent feature of the two hails that the water vapor was transported at the edge of the Tarim Basin and cloud clusters combination resulted in hail near the shear line.It could provide useful support for hail warning by comprehensive utilization of the highresolution satellites,weather radar and automatic station data to monitor and judge the development,retainment,movement and extinction of the hail cloud.
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