The spatial trends of dustfall of different sizes over northern China during April and May 2001,and March 2002,and their influencing factors,were analyzed.We divided the dustfall into seven grades based on particle si...The spatial trends of dustfall of different sizes over northern China during April and May 2001,and March 2002,and their influencing factors,were analyzed.We divided the dustfall into seven grades based on particle size.Total dustfall and dustfall for each grade were highest in desert regions then in regions undergoing desertification,and the total dustfall,dustfall 【100 μm and dustfall 】250 μm were higher in western agricultural regions closer to desert areas than in eastern agricultural regions.The spatial trends in dustfall 【300 μm in diameter were most strongly correlated with dust events,and the content of coarse particles increased with increasing severity of dust events.Because the spatial trend for dust events appears to be controlled by geomorphic conditions,vegetation coverage,soil moisture,and the distance from dust source,dustfall 【300 μm in diameter appears to have the same controlling factors as dust events,but the control decreases with increasing particle size.Wind,the driving force for dust emissions,also influenced the spatial trends in dustfall 【200 μm in diameter,and especially for dustfall 50 to 100 μm in diameter.Although dustfall 【300 μm in diameter and precipitation were not strongly spatially correlated,there is some evidence that high precipitation decreased deposition by restraining blowing sand.The coarser the dustfall,the weaker the correlation with wind speed;however,transport of larger particles still occurs,and further research will be required to test the possibility that this dust is entrained mainly by the small-scale dust devils that are commonly observed in the study area.展开更多
The study of the spatial patterns and temporal changes of cropland is important to understand the underlying factors and the functional effects of the agricultural landscape. On the other hand, crop dynamics mapping i...The study of the spatial patterns and temporal changes of cropland is important to understand the underlying factors and the functional effects of the agricultural landscape. On the other hand, crop dynamics mapping is essential to know the overall agro-spatial diversity of the area. Therefore, this paper addressed a spatio-temporal analysis of cropland and cropping pattern change in the Bogra district of Bangladesh over the last 16 years （between 1988/89 and 2004/05）. In this paper, crop mapping from multi-temporal and multi-sensor satellite images was described. Landsat TM and IRS P6 LlSS Ⅲ satellite images were used with GIS for spatial dynamics of cropland and cropping pattern change analysis. First, seasonal cropland maps were derived from object-based classification of satellite images, then two-date classified image differencing with GIS overlay technique and decision rules were applied. Cropping pattern change was analyzed in a spatial and quantitative way for the 16 years and for this, Integrated Land and Water Information System （ILWIS） and Land Change Modular （LCM） of IDRISl Andes were used. The results showed that in the area, mono crop cultivation was found in summer, but in winter, areas under different crop cultivation had changed dramatically. Change analysis showed that the changes mainly occurred in the north northwest and southwest of the areas, and during the time the highest change area was found under the rice-potato pattern.展开更多
The purpose of this study is to analyze the climatic characteristics and long-term spatial and temporal variations of haze occurrence in China. The impact factors of haze trends are also discussed. Meteorological data...The purpose of this study is to analyze the climatic characteristics and long-term spatial and temporal variations of haze occurrence in China. The impact factors of haze trends are also discussed. Meteorological data from 1961 to 2012 and daily PM10 concentrations from2003 to 2012 were employed in this study. The results indicate that the annual-average hazy days at all stations have been increasing rapidly from 4 days in 1961 to 18 days in 2012. The maximum number of haze days occur in winter（41.1%） while the minimum occur in summer（10.4%）. During 1961-2012, the high occurrence areas of haze shifted from central to south and east regions of China. The Beijing-Tianjin-Hebei（Jing-Jin-Ji） region, Shanxi,Shaanxi, and Henan Province are the high occurrence areas for haze, while the Yangtze River Delta（YRD） and the Pearl River Delta（PRD） have become regions with high haze occurrences in the last 25 years. Temperature and pressure are positively correlated with the number of haze days. However, wind, relative humidity, precipitation, and sunshine duration are negatively correlated with the number of haze days. The key meteorological factors affecting the formation and dissipation of haze vary for high and low altitudes, and are closely related to anthropogenic activities. In recent years, anthropogenic activities have played a more important role in haze occurrences compared with meteorological factors.展开更多
Integrated with GIS and remote sensing(RS) technology,a systematic analysis and its methodology for human-settlements social environment has been introduced.This methodology has been called spatial trend field model(S...Integrated with GIS and remote sensing(RS) technology,a systematic analysis and its methodology for human-settlements social environment has been introduced.This methodology has been called spatial trend field model(STFM).STFM's application history in the field of human-settlements social environment has been discussed at first.Then,some index data models have been created through STFM,which include population density trend field,human activity strength trend field,city-town spatial density trend field,urbanization ratio trend field,road density trend field,GDP spatial density trend field and PER-GDP spatial density trend field.With all above-mentioned indexes as input data,through Iterative Self-Organizing Data Analysis Techniques Algorithm(ISODATA),this paper makes a verification study of Chongqing municipality.The result of the case study confirms that STFM methodology is credible and has high efficiency for regional human-settlements study.展开更多
Extreme precipitation events pose significant challenges to water resources,ag-riculture,infrastructure,public health,ecosystems,energy production,fishing,timber production,and other rain-dependent socioeconomic secto...Extreme precipitation events pose significant challenges to water resources,ag-riculture,infrastructure,public health,ecosystems,energy production,fishing,timber production,and other rain-dependent socioeconomic sectors across Eastern Africa,threatening the environment and regional livelihoods.This study analyzes spatial and temporal trends of extreme precipitation in Eastern Africa from January 1981 to 2023,using high-resolution CHIRPS data.Key ex-treme precipitation indices,including R10mm,R75p,and SDII,were calculated to assess variations in the frequency,intensity,and contribution of extreme rainfall events.The temporal analysis reveals a statistically significant increas-ing trend in January precipitation(0.844 mm/year,p=0.0191),confirmed by Sen’s Slope(0.74 mm/year).R10mm increased by 0.036 days/year(p=0.0079),with Sen’s Slope estimating 0.04 days/year.R75p showed a rise of 0.025 days/year(p=0.0113),with Sen’s Slope at 0.02 days/year.SDII exhibited the most significant trend,increasing by 0.056 mm/day per year(p=0.0002),with Sen’s Slope at 0.06 mm/day per year.These results indicate a rise in extreme precipitation in Eastern Africa,increasing the risk of flooding and other cli-mate-related hazards.Spatial analysis shows distinct regional variations,with Southern Tanzania,Mozambique,Malawi,Zambia,Zimbabwe,and Madagas-car exhibiting statistically significant increasing trends in January precipitation and extreme precipitation indices.These regions are becoming more vulnera-ble to flooding and other climate-related hazards.Moreover,correlation anal-ysis identifies significant links between global SST anomalies and extreme pre-cipitation trends,demonstrating the influence of large-scale climate drivers.The study indicates the growing intensity and frequency of extreme precipita-tion in parts of Eastern Africa,significantly influenced by the South Pacific Convergence Zone(SPCZ).This necessitates a deeper understanding of SPCZ dynamics and their impacts on precipitation patterns to enhance climate pre-diction and develop adaptive strategies for mitigating extreme weather events.Such efforts will contribute to safeguarding water resources,agriculture,infra-structure,public health,energy production,fisheries,transportation,and live-lihoods across the region.展开更多
Based on the results of water sample measurements of nutrient concentrations at th e Datong Station of the Changjiang River from 1998 to 1999, combined w ith historical data of water quality, seasonal variations of nu...Based on the results of water sample measurements of nutrient concentrations at th e Datong Station of the Changjiang River from 1998 to 1999, combined w ith historical data of water quality, seasonal variations of nutrient concentrations and nutrient transports are discussed.The following results have been obtained: (1) the fluxes of the nitrate nitrogen, ammonium nitrogen and nitrite nitrogen increased by time-series from 1962 to 1990 , even if runoff volume had a little variation; (2) the concentrations and fluxes of the dissolved inorganic nitrogen (DIN) and dissolved in organic phosphorus (DIP) increased notably with time, but those of the dissolved silicon (DSI) decreased pronouncedly; and (3) the concentration s and fluxes changed synchronously with time between the Datong Station a nd the Changjiang Estuary.展开更多
An overview of the spatial and temporal variations of the environmental accidents in China in recent years was presented in this paper using available data.The results showed that the frequency of pollution accidents ...An overview of the spatial and temporal variations of the environmental accidents in China in recent years was presented in this paper using available data.The results showed that the frequency of pollution accidents was significantly decreased,from 3462 in 1990 to 462 in 2007.The water and air pollution accidents were found to be the dominant types,accounting for more than 80%of the total accidents.Considering the classification of environmental accidents at 4 scales,the general environmental accident,i.e.,the least serious type,was the most frequent event,taking up 58.98%of the total pollution accidents.In addition,the distribution of environmental accidents was generally in accordance with the industrial layout in the country during the past decade.It is very important to note that the extraordinarily severe environmental accidents showed an increasing trend in underdeveloped regions,which was caused by the transfer and the development of heavy polluted industry in these areas.As to the losses of environmental accidents,the casualties presented an obvious reduction tendency,while the direct economic loss per accident tended to climb up.Furthermore,some key factors that affect the spatial and temporal tendencies of environmental accidents in China were discussed and some suggestions were put forward,hoping to shed light on environmental risk management and emergency plans making associated with environmental accidents in China.展开更多
Daily snow data for 2300 climate stations covering the period from 1951 through 1980 have been used to monitor and diagnose secular variations,year-to-year fluctuations,and the spatial characteristics of snow variatio...Daily snow data for 2300 climate stations covering the period from 1951 through 1980 have been used to monitor and diagnose secular variations,year-to-year fluctuations,and the spatial characteristics of snow variation trends in China.An examination of time series reveals that there is a strong teleconnction to ENSO,to major volcanic eruptions, as well as to the CO_2-induced warming.The country-wide snow mass variations are positively correlated with global mean temperature,increasing during the current warming period and decreasing during the recent cooling period prior to the mid 1960s.A synchronous relationship exists between El Nino/Southern Oscillation and snowy winter in China. The year-to-year snow fluctuations seem to be generally out of phase with volcanic activity.The anomaly map shows that snow mass increased in high altitudes and moist regions,while it decreased in arid lowland and the southern bounda- ry zone during the warming period.The potential CO_2-induced changes in snow mass will further aggravate the regional differentiation between high mountains and lowlands,between moist and arid regions.The number of snow cover days will decrease in the northern lowlands,and snowfall will increase in the Qinghai-Xizang Plateau,high mountains,and the lower reaches of the Changjiang(Yangtze)River.展开更多
基金the Natural Science Foundation of China through grant No. 40638038
文摘The spatial trends of dustfall of different sizes over northern China during April and May 2001,and March 2002,and their influencing factors,were analyzed.We divided the dustfall into seven grades based on particle size.Total dustfall and dustfall for each grade were highest in desert regions then in regions undergoing desertification,and the total dustfall,dustfall 【100 μm and dustfall 】250 μm were higher in western agricultural regions closer to desert areas than in eastern agricultural regions.The spatial trends in dustfall 【300 μm in diameter were most strongly correlated with dust events,and the content of coarse particles increased with increasing severity of dust events.Because the spatial trend for dust events appears to be controlled by geomorphic conditions,vegetation coverage,soil moisture,and the distance from dust source,dustfall 【300 μm in diameter appears to have the same controlling factors as dust events,but the control decreases with increasing particle size.Wind,the driving force for dust emissions,also influenced the spatial trends in dustfall 【200 μm in diameter,and especially for dustfall 50 to 100 μm in diameter.Although dustfall 【300 μm in diameter and precipitation were not strongly spatially correlated,there is some evidence that high precipitation decreased deposition by restraining blowing sand.The coarser the dustfall,the weaker the correlation with wind speed;however,transport of larger particles still occurs,and further research will be required to test the possibility that this dust is entrained mainly by the small-scale dust devils that are commonly observed in the study area.
文摘The study of the spatial patterns and temporal changes of cropland is important to understand the underlying factors and the functional effects of the agricultural landscape. On the other hand, crop dynamics mapping is essential to know the overall agro-spatial diversity of the area. Therefore, this paper addressed a spatio-temporal analysis of cropland and cropping pattern change in the Bogra district of Bangladesh over the last 16 years （between 1988/89 and 2004/05）. In this paper, crop mapping from multi-temporal and multi-sensor satellite images was described. Landsat TM and IRS P6 LlSS Ⅲ satellite images were used with GIS for spatial dynamics of cropland and cropping pattern change analysis. First, seasonal cropland maps were derived from object-based classification of satellite images, then two-date classified image differencing with GIS overlay technique and decision rules were applied. Cropping pattern change was analyzed in a spatial and quantitative way for the 16 years and for this, Integrated Land and Water Information System （ILWIS） and Land Change Modular （LCM） of IDRISl Andes were used. The results showed that in the area, mono crop cultivation was found in summer, but in winter, areas under different crop cultivation had changed dramatically. Change analysis showed that the changes mainly occurred in the north northwest and southwest of the areas, and during the time the highest change area was found under the rice-potato pattern.
基金supported by the CMA’s special Funds for climate change(No.CCSF201439)the CMA’s special Funds for key technology(No.CMAGJ2015M79)the MEP’s Special Funds for Research on Public Welfares(No.201409002)
文摘The purpose of this study is to analyze the climatic characteristics and long-term spatial and temporal variations of haze occurrence in China. The impact factors of haze trends are also discussed. Meteorological data from 1961 to 2012 and daily PM10 concentrations from2003 to 2012 were employed in this study. The results indicate that the annual-average hazy days at all stations have been increasing rapidly from 4 days in 1961 to 18 days in 2012. The maximum number of haze days occur in winter（41.1%） while the minimum occur in summer（10.4%）. During 1961-2012, the high occurrence areas of haze shifted from central to south and east regions of China. The Beijing-Tianjin-Hebei（Jing-Jin-Ji） region, Shanxi,Shaanxi, and Henan Province are the high occurrence areas for haze, while the Yangtze River Delta（YRD） and the Pearl River Delta（PRD） have become regions with high haze occurrences in the last 25 years. Temperature and pressure are positively correlated with the number of haze days. However, wind, relative humidity, precipitation, and sunshine duration are negatively correlated with the number of haze days. The key meteorological factors affecting the formation and dissipation of haze vary for high and low altitudes, and are closely related to anthropogenic activities. In recent years, anthropogenic activities have played a more important role in haze occurrences compared with meteorological factors.
基金supported by National 11th Five-Year Technology Support Program (Grant No 2008BAH31B06)National Natural Science Foundation of China (Grant No50738007)
文摘Integrated with GIS and remote sensing(RS) technology,a systematic analysis and its methodology for human-settlements social environment has been introduced.This methodology has been called spatial trend field model(STFM).STFM's application history in the field of human-settlements social environment has been discussed at first.Then,some index data models have been created through STFM,which include population density trend field,human activity strength trend field,city-town spatial density trend field,urbanization ratio trend field,road density trend field,GDP spatial density trend field and PER-GDP spatial density trend field.With all above-mentioned indexes as input data,through Iterative Self-Organizing Data Analysis Techniques Algorithm(ISODATA),this paper makes a verification study of Chongqing municipality.The result of the case study confirms that STFM methodology is credible and has high efficiency for regional human-settlements study.
文摘Extreme precipitation events pose significant challenges to water resources,ag-riculture,infrastructure,public health,ecosystems,energy production,fishing,timber production,and other rain-dependent socioeconomic sectors across Eastern Africa,threatening the environment and regional livelihoods.This study analyzes spatial and temporal trends of extreme precipitation in Eastern Africa from January 1981 to 2023,using high-resolution CHIRPS data.Key ex-treme precipitation indices,including R10mm,R75p,and SDII,were calculated to assess variations in the frequency,intensity,and contribution of extreme rainfall events.The temporal analysis reveals a statistically significant increas-ing trend in January precipitation(0.844 mm/year,p=0.0191),confirmed by Sen’s Slope(0.74 mm/year).R10mm increased by 0.036 days/year(p=0.0079),with Sen’s Slope estimating 0.04 days/year.R75p showed a rise of 0.025 days/year(p=0.0113),with Sen’s Slope at 0.02 days/year.SDII exhibited the most significant trend,increasing by 0.056 mm/day per year(p=0.0002),with Sen’s Slope at 0.06 mm/day per year.These results indicate a rise in extreme precipitation in Eastern Africa,increasing the risk of flooding and other cli-mate-related hazards.Spatial analysis shows distinct regional variations,with Southern Tanzania,Mozambique,Malawi,Zambia,Zimbabwe,and Madagas-car exhibiting statistically significant increasing trends in January precipitation and extreme precipitation indices.These regions are becoming more vulnera-ble to flooding and other climate-related hazards.Moreover,correlation anal-ysis identifies significant links between global SST anomalies and extreme pre-cipitation trends,demonstrating the influence of large-scale climate drivers.The study indicates the growing intensity and frequency of extreme precipita-tion in parts of Eastern Africa,significantly influenced by the South Pacific Convergence Zone(SPCZ).This necessitates a deeper understanding of SPCZ dynamics and their impacts on precipitation patterns to enhance climate pre-diction and develop adaptive strategies for mitigating extreme weather events.Such efforts will contribute to safeguarding water resources,agriculture,infra-structure,public health,energy production,fisheries,transportation,and live-lihoods across the region.
基金National Natural Science Foundation of China,No.39790110
文摘Based on the results of water sample measurements of nutrient concentrations at th e Datong Station of the Changjiang River from 1998 to 1999, combined w ith historical data of water quality, seasonal variations of nutrient concentrations and nutrient transports are discussed.The following results have been obtained: (1) the fluxes of the nitrate nitrogen, ammonium nitrogen and nitrite nitrogen increased by time-series from 1962 to 1990 , even if runoff volume had a little variation; (2) the concentrations and fluxes of the dissolved inorganic nitrogen (DIN) and dissolved in organic phosphorus (DIP) increased notably with time, but those of the dissolved silicon (DSI) decreased pronouncedly; and (3) the concentration s and fluxes changed synchronously with time between the Datong Station a nd the Changjiang Estuary.
基金This work was supported by the National Hi-Tech Research and Development Program of China(863 Program)(No.2007AA06A404).
文摘An overview of the spatial and temporal variations of the environmental accidents in China in recent years was presented in this paper using available data.The results showed that the frequency of pollution accidents was significantly decreased,from 3462 in 1990 to 462 in 2007.The water and air pollution accidents were found to be the dominant types,accounting for more than 80%of the total accidents.Considering the classification of environmental accidents at 4 scales,the general environmental accident,i.e.,the least serious type,was the most frequent event,taking up 58.98%of the total pollution accidents.In addition,the distribution of environmental accidents was generally in accordance with the industrial layout in the country during the past decade.It is very important to note that the extraordinarily severe environmental accidents showed an increasing trend in underdeveloped regions,which was caused by the transfer and the development of heavy polluted industry in these areas.As to the losses of environmental accidents,the casualties presented an obvious reduction tendency,while the direct economic loss per accident tended to climb up.Furthermore,some key factors that affect the spatial and temporal tendencies of environmental accidents in China were discussed and some suggestions were put forward,hoping to shed light on environmental risk management and emergency plans making associated with environmental accidents in China.
基金This work was supported by the National Natural Science Foundation of China through Grant No.4880019.
文摘Daily snow data for 2300 climate stations covering the period from 1951 through 1980 have been used to monitor and diagnose secular variations,year-to-year fluctuations,and the spatial characteristics of snow variation trends in China.An examination of time series reveals that there is a strong teleconnction to ENSO,to major volcanic eruptions, as well as to the CO_2-induced warming.The country-wide snow mass variations are positively correlated with global mean temperature,increasing during the current warming period and decreasing during the recent cooling period prior to the mid 1960s.A synchronous relationship exists between El Nino/Southern Oscillation and snowy winter in China. The year-to-year snow fluctuations seem to be generally out of phase with volcanic activity.The anomaly map shows that snow mass increased in high altitudes and moist regions,while it decreased in arid lowland and the southern bounda- ry zone during the warming period.The potential CO_2-induced changes in snow mass will further aggravate the regional differentiation between high mountains and lowlands,between moist and arid regions.The number of snow cover days will decrease in the northern lowlands,and snowfall will increase in the Qinghai-Xizang Plateau,high mountains,and the lower reaches of the Changjiang(Yangtze)River.
