Rain-on-snow(ROS)events involve rainfall on snow surfaces,and the occurrence of ROS events can exacerbate water scarcity and ecosystem vulnerability in the arid region of Northwest China(ARNC).In this study,using dail...Rain-on-snow(ROS)events involve rainfall on snow surfaces,and the occurrence of ROS events can exacerbate water scarcity and ecosystem vulnerability in the arid region of Northwest China(ARNC).In this study,using daily snow depth data and daily meteorological data from 68 meteorological stations provided by the China Meteorological Administration National Meteorological Information Centre,we investigated the spatiotemporal variability of ROS events in the ARNC from 1978 to 2015 and examined the factors affecting these events and possible changes of future ROS events in the ARNC.The results showed that ROS events in the ARNC mainly occurred from October to May of the following year and were largely distributed in the Qilian Mountains,Tianshan Mountains,Ili River Valley,Tacheng Prefecture,and Altay Prefecture,with the Ili River Valley,Tacheng City,and Altay Mountains exhibiting the most occurrences.Based on the intensity of ROS events,the areas with the highest risk of flooding resulting from ROS events in the ARNC were the Tianshan Mountains,Ili River Valley,Tacheng City,and Altay Mountains.The number and intensity of ROS events in the ARNC largely increased from 1978 to 2015,mainly influenced by air temperature and the number of rainfall days.However,due to the snowpack abundance in areas experiencing frequent ROS events in the ARNC,snowpack changes exerted slight impact on ROS events,which is a temporary phenomenon.Furthermore,elevation imposed lesser impact on ROS events in the ARNC than other factors.In the ARNC,the start time of rainfall and the end time of snowpack gradually advanced from the spring of the current year to the winter of the previous year,while the end time of rainfall and the start time of snowpack gradually delayed from autumn to winter.This may lead to more ROS events in winter in the future.These results could provide a sound basis for managing water resources and mitigating related disasters caused by ROS events in the ARNC.展开更多
The increasing shortage in water resources is a key factor affecting sustainable socio-economic development in the arid region of Northwest China(ARNC). Water shortages also affect the stability of the region's oa...The increasing shortage in water resources is a key factor affecting sustainable socio-economic development in the arid region of Northwest China(ARNC). Water shortages also affect the stability of the region's oasis ecosystem. This paper summarizes the hydrological processes and water cycle of inland river basins in the ARNC, focusing on the following aspects: the spatial-temporal features of water resources(including air water vapor resources, runoff, and glacial meltwater) and their driving forces; the characteristics of streamflow composition in the inland river basins; the characteristics and main controlling factors of baseflow in the inland rivers; and anticipated future changes in hydrological processes and water resources. The results indicate that:(1) although the runoff in most inland rivers in the ARNC showed a significant increasing trend, both the glaciated area and glacial ice reserves have been reduced in the mountains;(2) snow melt and glacier melt are extremely important hydrological processes in the ARNC, especially in the Kunlun and Tianshan mountains;(3) baseflow in the inland rivers of the ARNC is the result of climate change and human activities, with the main driving factors being the reduction in forest area and the over-exploitation and utilization of groundwater in the river basins; and(4) the contradictions among water resources, ecology and economy will further increase in the future. The findings of this study might also help strengthen the ecological, economic and social sustainable development in the study region.展开更多
This study reviews the latest progress in research on climate change and water resources in the arid region of Northwest China, analyzes the cause of water resource changes within the region from the perspective of cl...This study reviews the latest progress in research on climate change and water resources in the arid region of Northwest China, analyzes the cause of water resource changes within the region from the perspective of climate change and human activities, and summarizes future likely changes in water resources and associated adaptation strategies. The research shows that the climate in the region has experienced warming and wetting with the most significant warming in winter and the highest increase in summer precipitation since 1961. Areas with the most significant warming trends include the Qaidam Basin, the Yili River Valley, and Tacheng. Spatially, the increasing trend in precipitation becomes increasingly significant from the southeast to the northwest, and northern Xinjiang experienced the highest increase. Studies have shown a decrease in headwater of Shiyang River because runoff is mainly based on precipitation which shows a decrease trend. But an increase in western rivers was observed such as Tarim River and Shule River as well as Heihe River due to rapid glacier shrinkage and snowmelt as well as precipitation increase in mountain area. Meanwhile unreasonable human activities resulted in decrease of runoff in the middle and lower reaches of Haihe River, Shiyang River and Kaidu River. Finally, recommendations for future studies are suggested that include characteristics of changes in extreme weather events and their impacts on water resources, projections of future climate and water resource changes, climate change attribution, the selection of adaptation strategies relating to climate change and social economic activities, and use of scientific methods to quantitatively determine water resource allocation.展开更多
[Objective] The aim was to study the relationship between spring precipitation anomaly in Northwest China and sea surface temperature anomaly (SSTA) in Key region in recent 50 years. [Method] Based on monthly average ...[Objective] The aim was to study the relationship between spring precipitation anomaly in Northwest China and sea surface temperature anomaly (SSTA) in Key region in recent 50 years. [Method] Based on monthly average precipitation in Northwest China and global monthly sea surface temperature (SST) grid data, the effects of SSTA in equatorial central and eastern Pacific on spring precipitation in Northwest China were discussed by means of correlation and SVD analysis. [Result] For spring precipitation in Northwest China, the key period of SST was from August to September in the former year, and the equatorial central and eastern Pacific (125°-85° W, 5° S-10° N) was named 'Key region'. Correlation analysis showed that there was obviously positive correlation between spring precipitation in Northwest China and SST (monthly average from August to September in the former year) in equatorial central and eastern Pacific, especially Key region. SVD analysis revealed that spring precipitation anomaly in Northwest China distributed in phase, while SST in equatorial central and eastern Pacific from August to September in the former year had higher positive correlation coefficient, and there was obviously positive couple correlation in Key region. [Conclusion] The study could provide theoretic foundation for the prediction of drought and flood in Northwest China.展开更多
[Objective] The research aimed to study the correlated characteristics between spring precipitation in the arid region of Northwest China and global sea surface temperature. [Method] Based on GPCP global monthly preci...[Objective] The research aimed to study the correlated characteristics between spring precipitation in the arid region of Northwest China and global sea surface temperature. [Method] Based on GPCP global monthly precipitation data and NOAA ERSST sea surface temperature data during 1979-2008, the precipitation characteristics in the arid region of Northwest China in 30 years and its correlated distribution characteristics with the global sea surface temperature were analyzed by using the correlation and composite analysis methods. [Result] Spring rainfall presented the fluctuation increasing in the arid region of Northwest China during 1979-2008. The sea surface temperature of Indian Ocean in 15° S-22° N, 45°-105° E had the continuous influence on spring precipitation in the arid region of Northwest China. It could be as a stable factor for forecasting spring precipitation in the arid region zone of Northwest China. When the sea surface temperature was higher in Indian Ocean, Bay of Bengal and Arabian Sea, maybe spring precipitation in the arid region of Northwest China was more. If the sea surface temperature in the equatorial Eastern Pacific Ocean in prior summer, autumn and winter was higher, it was favorable for spring precipitation in the arid region of Northwest China in the next year. The sea surface temperature field in Arabian Sea, Central Indian Ocean and Western Pacific Ocean was the key factor which affected spring precipitation in the arid region of Northwest China. [Conclusion] The research provided the theory basis for the prediction and forecast of precipitation in the arid region.展开更多
Quantitative assessment of the impact of groundwater depletion on phreatophytes in(hyper-)arid regions is key to sustainable groundwater management.However,a parsimonious model for predicting the response of phreatoph...Quantitative assessment of the impact of groundwater depletion on phreatophytes in(hyper-)arid regions is key to sustainable groundwater management.However,a parsimonious model for predicting the response of phreatophytes to a decrease of the water table is lacking.A variable saturated flow model,HYDRUS-1D,was used to numerically assess the influences of depth to the water table(DWT)and mean annual precipitation(MAP)on transpiration of groundwater-dependent vegetation in(hyper-)arid regions of northwest China.An exponential relationship is found for the normalized transpiration(a ratio of transpiration at a certain DWT to transpiration at 1 m depth,T_(a)^(*))with increasing DWT,while a positive linear relationship is identified between T_(a)^(*)and annual precipitation.Sensitivity analysis shows that the model is insensitive to parameters,such as saturated soil hydraulic conductivity and water stress parameters,indicated by an insignificant variation(less than 20%in most cases)under±50%changes of these parameters.Based on these two relationships,a universal model has been developed to predict the response of phreatophyte transpiration to groundwater drawdown for(hyper-)arid regions using MAP only.The estimated T_(a)^(*)from the model is reasonable by comparing with published measured values.展开更多
Making use of observation data of GPS in the Northwest China region and infrared distancemeasurements crossing the Qilian-Longshoushan fault zone up to 2004, aided by the least square collocation and inversion of nega...Making use of observation data of GPS in the Northwest China region and infrared distancemeasurements crossing the Qilian-Longshoushan fault zone up to 2004, aided by the least square collocation and inversion of negative dislocation model for the boundaries of elastic blocks and the singular force-source, the dynamic evolution features of deformation and strain fields before and after the Ms = 8. 1 earthquake on the west of Kunlun Mountains Pass, especially the recent tectonic deformation and stress field status three years after this earthquake are studied. The possible regions or segments of active blocks and their boundaries reflecting accumulation background of high strain energy of producing earthquakes over middle magnitude, are obtained, as well as the potential epicenter. The results show that after shortterm relaxation and adjustment in the northern margin of Qinghai-Xizang （Tibet） block after the Ms = 8. 1 earthquake, the main control action of background field of northeastward pushing of Indian plate is now recovering. Moreover, the following regions are found to have the background of high strain energy accumulation. They are the middle segment of the northern Tianshan fault zone and its meeting region with the western segment, the middle and western segments of southern Tianshan fault zone and the meeting region with Western Kunlun fault zone, the middle segment of Altun fault, the middle-eastern segment of Qilianshan fault zone and its meeting region with Haiyuan fault, the meeting region of northern margin fault of west Qinling Range and the southeastward expanding line of Zhuanglanghe fault; The Linze and Haiynan areas also see accumulation of strain energy to some degree.展开更多
Based on introducing the basic conditions of the ethnic regions in northwest Sichuan Province,the thesis analyzes its agricultural development status,which can be classified into two aspects--rich natural resources an...Based on introducing the basic conditions of the ethnic regions in northwest Sichuan Province,the thesis analyzes its agricultural development status,which can be classified into two aspects--rich natural resources and slow agricultural economic growth.Through the analysis on the agricultural structure of northwest Sichuan Province,it is found that the production efficiency and economic benefits of crop planting in this region are low,animal husbandry,as a major industry in pastoral region,sees high production efficiency,the agricultural production is still at the resource-oriented stage;its agricultural structure is still the farming-pastoral structure relying mainly on animal husbandry,planting is dominated by crop planting and potato planting,animal husbandry mainly produces dairy and beef;the ethnic regions in northwest Sichuan Province is endowed with the advantages to grow crops,beans and fruits as well as to produce beef,mutton and milk,among which,three industries,say fruit,beef and dairy are with increasing location quotient and gradually strengthening industrial comparative advantage,while the location quotient of the other industries is declining and their industrial comparative advantages are more stable.In order to promote the agriculture in northwest Sichuan Province to develop in breadth and depth,the thesis proposes the following measures and suggestions:the first one is to adhere to the development strategy of modern animal husbandry;the second is to appropriately improve the proportion of economic crops;the third is to accelerate the development of green food processing industry.展开更多
[Objective] The twice regional rainstorms in northwest Yantai in July in 2009 and July in 2010 were expounded.[Method] The twice regional rainstorm in northwest Yantai in July in 2009 and July in 2010 were selected fo...[Objective] The twice regional rainstorms in northwest Yantai in July in 2009 and July in 2010 were expounded.[Method] The twice regional rainstorm in northwest Yantai in July in 2009 and July in 2010 were selected for comparison analysis by dint of conventional and non-conventional weather data,from the aspects of circulation background,physics quantity,and radar echo,etc.[Result] The twice large rainstorm process were regional convective strong precipitation.The rainstorm fell in the northwest of Yantai and had a strong precipitation center above 200 mm.The twice large rainstorm was affected by subtropical and shear line.The rainstorm area was related to the location of 588 dagpm line,westerly trough,and shear line.It was regional rainstorm of typical subtropical edge warm and wet airstream,combination of low vortex and shear line of westerly.The precipitation occurred around the center of water vapor flux;K index had pretty good indication effects to the generation of rainstorm.Large rainstorm occurred around the place with high K index.The K index of twice large rainstorm was larger than or equal to 34 ℃,and was close to the rainstorm falling area where K index was larger than or equal to 35 ℃.The reflection factor of twice large rainstorms at 0.5° elevation,the largest echo intensity was from 55 to 60 dBz,in strip echo from south to north,through the west peninsula,forming train effect.The data report product also had important reference basis for the report of regional large rainstorm.[Conclusion] The study provided references and basis for the report of large rainstorm in the future.展开更多
Understory plants are important components of forest ecosystems and play a crucial role in regulating community structures,function realization,and community succession.However,little is known about how abiotic and bi...Understory plants are important components of forest ecosystems and play a crucial role in regulating community structures,function realization,and community succession.However,little is known about how abiotic and biotic drivers affect the diversity of understory species in cold temperate coniferous forests in the semiarid climate region of North China.We hypothesized that(1)topographic factors are important environmental factors affecting the distribution and variation of understory strata,and(2)different understory strata respond differently to environmental factors;shrubs may be significantly affected by the overstory stratum,and herbs may be more affected by surface soil conditions.To test these hypotheses,we used the boosted regression tree method to analyze abiotic and biotic environmental factors that influence understory species diversity,using data from 280 subplots across 56 sites in cold temperate coniferous forests of North China.Elevation and slope aspect were the dominant and indirect abiotic drivers affecting understory species diversity,and individual tree size inequality(DBH variation)was the dominant biotic driver of understory species diversity;soil water content was the main edaphic factors affecting herb layers.Elevation,slope aspect,and DBH variation accounted for 36.4,14.5,and 12.1%,respectively,of shrub stratum diversity.Shrub diversity decreased with elevation within the range of altitude of this study,but increased with DBH variation;shrub diversity was highest on north-oriented slopes.The strongest factor affecting herb stratum species diversity was slope aspect,accounting for 25.9%of the diversity,followed by elevation(15.7%),slope(12.2%),and soil water content(10.3%).The highest herb diversity was found on southeast-oriented slopes and the lowest on northeast-oriented slopes;herb diversity decreased with elevation and soil water content,but increased with slope.The results of the study provide a reference for scientific management and biodiversity protection in cold temperate coniferous forests of North China.展开更多
Distribution of rainfall event sizes and interval lengths between events are important characteristics of arid and semi-arid climates. Understanding their importance will contribute to our ability to understand ecosys...Distribution of rainfall event sizes and interval lengths between events are important characteristics of arid and semi-arid climates. Understanding their importance will contribute to our ability to understand ecosystem dynamics in these regions. Rainfall event timing and magnitude are important drivers of ecosystem processes and are instrumental in creating land-scape heterogeneity in arid and semi-arid regions. Rainfall event characteristics were analyzed using an automatic tip-ping-bucket rain-gauge record across the entire summer monsoon season from 2008 to 2015 at the arid desert area of Shapotou in the Tengger Desert, China. Changing the minimum inter-event time （MIT） from 30 min to 24 h alters the number of rainfall events from 64 to 25 for the event depth larger than 0.1 mm. The mean rainfall intensity declined from 0.95 mm/h to 0.53 mm/h, and the geometric mean event duration rose from 0.55 h to 4.4 h. The number of rainfall events, mean rainfall intensity, and geometric mean event duration differed under different criteria of individual rainfall depths, except that for an individual rainfall depth of 0.5, 1.0, and 5.0 mm. The aforementioned features differed only at the lowest range of the mean rainfall intensity and depth for MIT=3 and 6 h. These findings suggest that identification of event-based rainfall in this specific arid region can be better achieved by setting the MIT at six hours. The wide variation in rainfall event properties indicate the need for paying more attention to the proper selection and reporting of event criteria in studies that adopt event-based data analysis. This is especially true in quantifying effective rainfall for soil water replenishment in terms of rainfall depth and intensity with infrequent rainfall events.展开更多
基金funded by the National Natural Science Foundation of China(42171145,42171147)the Gansu Provincial Science and Technology Program(22ZD6FA005)the Key Talent Program of Gansu Province.
文摘Rain-on-snow(ROS)events involve rainfall on snow surfaces,and the occurrence of ROS events can exacerbate water scarcity and ecosystem vulnerability in the arid region of Northwest China(ARNC).In this study,using daily snow depth data and daily meteorological data from 68 meteorological stations provided by the China Meteorological Administration National Meteorological Information Centre,we investigated the spatiotemporal variability of ROS events in the ARNC from 1978 to 2015 and examined the factors affecting these events and possible changes of future ROS events in the ARNC.The results showed that ROS events in the ARNC mainly occurred from October to May of the following year and were largely distributed in the Qilian Mountains,Tianshan Mountains,Ili River Valley,Tacheng Prefecture,and Altay Prefecture,with the Ili River Valley,Tacheng City,and Altay Mountains exhibiting the most occurrences.Based on the intensity of ROS events,the areas with the highest risk of flooding resulting from ROS events in the ARNC were the Tianshan Mountains,Ili River Valley,Tacheng City,and Altay Mountains.The number and intensity of ROS events in the ARNC largely increased from 1978 to 2015,mainly influenced by air temperature and the number of rainfall days.However,due to the snowpack abundance in areas experiencing frequent ROS events in the ARNC,snowpack changes exerted slight impact on ROS events,which is a temporary phenomenon.Furthermore,elevation imposed lesser impact on ROS events in the ARNC than other factors.In the ARNC,the start time of rainfall and the end time of snowpack gradually advanced from the spring of the current year to the winter of the previous year,while the end time of rainfall and the start time of snowpack gradually delayed from autumn to winter.This may lead to more ROS events in winter in the future.These results could provide a sound basis for managing water resources and mitigating related disasters caused by ROS events in the ARNC.
基金supported by the National Natural Science Foundation of China (41630859)the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA19030204)
文摘The increasing shortage in water resources is a key factor affecting sustainable socio-economic development in the arid region of Northwest China(ARNC). Water shortages also affect the stability of the region's oasis ecosystem. This paper summarizes the hydrological processes and water cycle of inland river basins in the ARNC, focusing on the following aspects: the spatial-temporal features of water resources(including air water vapor resources, runoff, and glacial meltwater) and their driving forces; the characteristics of streamflow composition in the inland river basins; the characteristics and main controlling factors of baseflow in the inland rivers; and anticipated future changes in hydrological processes and water resources. The results indicate that:(1) although the runoff in most inland rivers in the ARNC showed a significant increasing trend, both the glaciated area and glacial ice reserves have been reduced in the mountains;(2) snow melt and glacier melt are extremely important hydrological processes in the ARNC, especially in the Kunlun and Tianshan mountains;(3) baseflow in the inland rivers of the ARNC is the result of climate change and human activities, with the main driving factors being the reduction in forest area and the over-exploitation and utilization of groundwater in the river basins; and(4) the contradictions among water resources, ecology and economy will further increase in the future. The findings of this study might also help strengthen the ecological, economic and social sustainable development in the study region.
文摘This study reviews the latest progress in research on climate change and water resources in the arid region of Northwest China, analyzes the cause of water resource changes within the region from the perspective of climate change and human activities, and summarizes future likely changes in water resources and associated adaptation strategies. The research shows that the climate in the region has experienced warming and wetting with the most significant warming in winter and the highest increase in summer precipitation since 1961. Areas with the most significant warming trends include the Qaidam Basin, the Yili River Valley, and Tacheng. Spatially, the increasing trend in precipitation becomes increasingly significant from the southeast to the northwest, and northern Xinjiang experienced the highest increase. Studies have shown a decrease in headwater of Shiyang River because runoff is mainly based on precipitation which shows a decrease trend. But an increase in western rivers was observed such as Tarim River and Shule River as well as Heihe River due to rapid glacier shrinkage and snowmelt as well as precipitation increase in mountain area. Meanwhile unreasonable human activities resulted in decrease of runoff in the middle and lower reaches of Haihe River, Shiyang River and Kaidu River. Finally, recommendations for future studies are suggested that include characteristics of changes in extreme weather events and their impacts on water resources, projections of future climate and water resource changes, climate change attribution, the selection of adaptation strategies relating to climate change and social economic activities, and use of scientific methods to quantitatively determine water resource allocation.
文摘[Objective] The aim was to study the relationship between spring precipitation anomaly in Northwest China and sea surface temperature anomaly (SSTA) in Key region in recent 50 years. [Method] Based on monthly average precipitation in Northwest China and global monthly sea surface temperature (SST) grid data, the effects of SSTA in equatorial central and eastern Pacific on spring precipitation in Northwest China were discussed by means of correlation and SVD analysis. [Result] For spring precipitation in Northwest China, the key period of SST was from August to September in the former year, and the equatorial central and eastern Pacific (125°-85° W, 5° S-10° N) was named 'Key region'. Correlation analysis showed that there was obviously positive correlation between spring precipitation in Northwest China and SST (monthly average from August to September in the former year) in equatorial central and eastern Pacific, especially Key region. SVD analysis revealed that spring precipitation anomaly in Northwest China distributed in phase, while SST in equatorial central and eastern Pacific from August to September in the former year had higher positive correlation coefficient, and there was obviously positive couple correlation in Key region. [Conclusion] The study could provide theoretic foundation for the prediction of drought and flood in Northwest China.
基金Supported by Public Welfare Industry Special Project of China Meteorological Administration(201006023)
文摘[Objective] The research aimed to study the correlated characteristics between spring precipitation in the arid region of Northwest China and global sea surface temperature. [Method] Based on GPCP global monthly precipitation data and NOAA ERSST sea surface temperature data during 1979-2008, the precipitation characteristics in the arid region of Northwest China in 30 years and its correlated distribution characteristics with the global sea surface temperature were analyzed by using the correlation and composite analysis methods. [Result] Spring rainfall presented the fluctuation increasing in the arid region of Northwest China during 1979-2008. The sea surface temperature of Indian Ocean in 15° S-22° N, 45°-105° E had the continuous influence on spring precipitation in the arid region of Northwest China. It could be as a stable factor for forecasting spring precipitation in the arid region zone of Northwest China. When the sea surface temperature was higher in Indian Ocean, Bay of Bengal and Arabian Sea, maybe spring precipitation in the arid region of Northwest China was more. If the sea surface temperature in the equatorial Eastern Pacific Ocean in prior summer, autumn and winter was higher, it was favorable for spring precipitation in the arid region of Northwest China in the next year. The sea surface temperature field in Arabian Sea, Central Indian Ocean and Western Pacific Ocean was the key factor which affected spring precipitation in the arid region of Northwest China. [Conclusion] The research provided the theory basis for the prediction and forecast of precipitation in the arid region.
基金This research was funded by projects of the China Geological Survey(12120113104100 and DD20190351)National Natural Science Foundation of China(41877199)Shaanxi Science and Technology Department(2019TD-040,2021ZDLSF05-01).
文摘Quantitative assessment of the impact of groundwater depletion on phreatophytes in(hyper-)arid regions is key to sustainable groundwater management.However,a parsimonious model for predicting the response of phreatophytes to a decrease of the water table is lacking.A variable saturated flow model,HYDRUS-1D,was used to numerically assess the influences of depth to the water table(DWT)and mean annual precipitation(MAP)on transpiration of groundwater-dependent vegetation in(hyper-)arid regions of northwest China.An exponential relationship is found for the normalized transpiration(a ratio of transpiration at a certain DWT to transpiration at 1 m depth,T_(a)^(*))with increasing DWT,while a positive linear relationship is identified between T_(a)^(*)and annual precipitation.Sensitivity analysis shows that the model is insensitive to parameters,such as saturated soil hydraulic conductivity and water stress parameters,indicated by an insignificant variation(less than 20%in most cases)under±50%changes of these parameters.Based on these two relationships,a universal model has been developed to predict the response of phreatophyte transpiration to groundwater drawdown for(hyper-)arid regions using MAP only.The estimated T_(a)^(*)from the model is reasonable by comparing with published measured values.
基金The research was sponsored bythe 10th"Five-Year Plan"keyresearch program of short-term earthquake prediction of CEA (2004BA601B01-01-03) the 11th"Five-YearPlan"key research programof earthquake prediction(preparatory research) .
文摘Making use of observation data of GPS in the Northwest China region and infrared distancemeasurements crossing the Qilian-Longshoushan fault zone up to 2004, aided by the least square collocation and inversion of negative dislocation model for the boundaries of elastic blocks and the singular force-source, the dynamic evolution features of deformation and strain fields before and after the Ms = 8. 1 earthquake on the west of Kunlun Mountains Pass, especially the recent tectonic deformation and stress field status three years after this earthquake are studied. The possible regions or segments of active blocks and their boundaries reflecting accumulation background of high strain energy of producing earthquakes over middle magnitude, are obtained, as well as the potential epicenter. The results show that after shortterm relaxation and adjustment in the northern margin of Qinghai-Xizang （Tibet） block after the Ms = 8. 1 earthquake, the main control action of background field of northeastward pushing of Indian plate is now recovering. Moreover, the following regions are found to have the background of high strain energy accumulation. They are the middle segment of the northern Tianshan fault zone and its meeting region with the western segment, the middle and western segments of southern Tianshan fault zone and the meeting region with Western Kunlun fault zone, the middle segment of Altun fault, the middle-eastern segment of Qilianshan fault zone and its meeting region with Haiyuan fault, the meeting region of northern margin fault of west Qinling Range and the southeastward expanding line of Zhuanglanghe fault; The Linze and Haiynan areas also see accumulation of strain energy to some degree.
基金Supported by "Research on Evaluation of Agricultural Resources and Construction of Industrial Aggregation Model in Sichuan Province"(08ZQ026-005)Sichuan Youth Foundation
文摘Based on introducing the basic conditions of the ethnic regions in northwest Sichuan Province,the thesis analyzes its agricultural development status,which can be classified into two aspects--rich natural resources and slow agricultural economic growth.Through the analysis on the agricultural structure of northwest Sichuan Province,it is found that the production efficiency and economic benefits of crop planting in this region are low,animal husbandry,as a major industry in pastoral region,sees high production efficiency,the agricultural production is still at the resource-oriented stage;its agricultural structure is still the farming-pastoral structure relying mainly on animal husbandry,planting is dominated by crop planting and potato planting,animal husbandry mainly produces dairy and beef;the ethnic regions in northwest Sichuan Province is endowed with the advantages to grow crops,beans and fruits as well as to produce beef,mutton and milk,among which,three industries,say fruit,beef and dairy are with increasing location quotient and gradually strengthening industrial comparative advantage,while the location quotient of the other industries is declining and their industrial comparative advantages are more stable.In order to promote the agriculture in northwest Sichuan Province to develop in breadth and depth,the thesis proposes the following measures and suggestions:the first one is to adhere to the development strategy of modern animal husbandry;the second is to appropriately improve the proportion of economic crops;the third is to accelerate the development of green food processing industry.
文摘[Objective] The twice regional rainstorms in northwest Yantai in July in 2009 and July in 2010 were expounded.[Method] The twice regional rainstorm in northwest Yantai in July in 2009 and July in 2010 were selected for comparison analysis by dint of conventional and non-conventional weather data,from the aspects of circulation background,physics quantity,and radar echo,etc.[Result] The twice large rainstorm process were regional convective strong precipitation.The rainstorm fell in the northwest of Yantai and had a strong precipitation center above 200 mm.The twice large rainstorm was affected by subtropical and shear line.The rainstorm area was related to the location of 588 dagpm line,westerly trough,and shear line.It was regional rainstorm of typical subtropical edge warm and wet airstream,combination of low vortex and shear line of westerly.The precipitation occurred around the center of water vapor flux;K index had pretty good indication effects to the generation of rainstorm.Large rainstorm occurred around the place with high K index.The K index of twice large rainstorm was larger than or equal to 34 ℃,and was close to the rainstorm falling area where K index was larger than or equal to 35 ℃.The reflection factor of twice large rainstorms at 0.5° elevation,the largest echo intensity was from 55 to 60 dBz,in strip echo from south to north,through the west peninsula,forming train effect.The data report product also had important reference basis for the report of regional large rainstorm.[Conclusion] The study provided references and basis for the report of large rainstorm in the future.
基金supported by the National Natural Science Foundation of China(Grant No.31470630)Shanxi Forestry Science and Technology Innovation Project
文摘Understory plants are important components of forest ecosystems and play a crucial role in regulating community structures,function realization,and community succession.However,little is known about how abiotic and biotic drivers affect the diversity of understory species in cold temperate coniferous forests in the semiarid climate region of North China.We hypothesized that(1)topographic factors are important environmental factors affecting the distribution and variation of understory strata,and(2)different understory strata respond differently to environmental factors;shrubs may be significantly affected by the overstory stratum,and herbs may be more affected by surface soil conditions.To test these hypotheses,we used the boosted regression tree method to analyze abiotic and biotic environmental factors that influence understory species diversity,using data from 280 subplots across 56 sites in cold temperate coniferous forests of North China.Elevation and slope aspect were the dominant and indirect abiotic drivers affecting understory species diversity,and individual tree size inequality(DBH variation)was the dominant biotic driver of understory species diversity;soil water content was the main edaphic factors affecting herb layers.Elevation,slope aspect,and DBH variation accounted for 36.4,14.5,and 12.1%,respectively,of shrub stratum diversity.Shrub diversity decreased with elevation within the range of altitude of this study,but increased with DBH variation;shrub diversity was highest on north-oriented slopes.The strongest factor affecting herb stratum species diversity was slope aspect,accounting for 25.9%of the diversity,followed by elevation(15.7%),slope(12.2%),and soil water content(10.3%).The highest herb diversity was found on southeast-oriented slopes and the lowest on northeast-oriented slopes;herb diversity decreased with elevation and soil water content,but increased with slope.The results of the study provide a reference for scientific management and biodiversity protection in cold temperate coniferous forests of North China.
基金funded by the National Natural Science Foundation of China (Grant Nos. 41530750, 41501108 and 41371101)
文摘Distribution of rainfall event sizes and interval lengths between events are important characteristics of arid and semi-arid climates. Understanding their importance will contribute to our ability to understand ecosystem dynamics in these regions. Rainfall event timing and magnitude are important drivers of ecosystem processes and are instrumental in creating land-scape heterogeneity in arid and semi-arid regions. Rainfall event characteristics were analyzed using an automatic tip-ping-bucket rain-gauge record across the entire summer monsoon season from 2008 to 2015 at the arid desert area of Shapotou in the Tengger Desert, China. Changing the minimum inter-event time （MIT） from 30 min to 24 h alters the number of rainfall events from 64 to 25 for the event depth larger than 0.1 mm. The mean rainfall intensity declined from 0.95 mm/h to 0.53 mm/h, and the geometric mean event duration rose from 0.55 h to 4.4 h. The number of rainfall events, mean rainfall intensity, and geometric mean event duration differed under different criteria of individual rainfall depths, except that for an individual rainfall depth of 0.5, 1.0, and 5.0 mm. The aforementioned features differed only at the lowest range of the mean rainfall intensity and depth for MIT=3 and 6 h. These findings suggest that identification of event-based rainfall in this specific arid region can be better achieved by setting the MIT at six hours. The wide variation in rainfall event properties indicate the need for paying more attention to the proper selection and reporting of event criteria in studies that adopt event-based data analysis. This is especially true in quantifying effective rainfall for soil water replenishment in terms of rainfall depth and intensity with infrequent rainfall events.
