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1.
The glacier mass balance(GMB) is an important link between climate and water resources and has remarkable regulatory functions in river runoff. To simulate changes of the GMB and to analyze the recharge rates of glacier meltwater to runoff in the Manas River Basin(MRB) during 2000–2016, MOD11 C3, TRMM 3 B43 and other multi-source remote sensing data were used to drive the degree-day model. The results showed that:(1) the accuracy of the remote sensing meteorological data can be corrected effectively by constructing the temperature and precipitation inversion models, and the characteristics of glacial climate can be finely described through downscaling. The average annual temperature was –7.57 °C and the annual precipitation was 410.71 mm in the glacier area of the MRB. The zone at an altitude of about 4200 m was a severe climate change zone, and above and below that zone, the temperature drop rates were –0.03°C/100 m and –0.57°C/100 m, respectively, while precipitation gradients were –2.66 mm/100 m and 4.89 mm/100 m, respectively.(2) The overall GMB was negative with a cumulative GMB of up to –9811.19 mm w.e. and the average annual GMB fluctuated between –464.85 and –632.19 mm w.e. Besides, the glacier melted slowly during 2000–2002 and 2008–2010, but rapidly for 2002–2008 and 2010–2016, while the most serious loss of the glacier occurred in 2005–2009. Moreover, the vertical changes of the GMB increased at 244.83 mm w.e./100 m in the ablation zone but only at 18.77 mm w.e./100 m in the accumulation zone.(3) The intraannual runoff strongly responded to the change of the GMB especially in July and August when the loss of the GMB accounted for 75.4% of the annual loss, and when runoff accounted for 55.1% of the annual total. Due to differences in the annual precipitation and snow meltwater outside the glacier, the interannual glacier meltwater recharge rates fluctuated between 19% and 31%. The recharge rate of glacier meltwater to runoff in the MRB was close to that for other basins in the Tianshan Mountains, which may be used as a basis to confirm the reliability of the estimated GMB results. Furthermore, based on the present findings, it is recommended that the research community pursue studies on the GMB in other alpine river basins. 相似文献
2.
FAN Zemeng 《地理学报(英文版)》2021,31(4):497-517
Explicitly identifying the spatial distribution of ecological transition zones(ETZs) and simulating their response to climate scenarios is of significance in understanding the response and feedback of ecosystems to global climate change. In this study, a quantitative spatial identification method was developed to assess ETZ distribution in terms of the improved Holdridge life zone(iHLZ) model. Based on climate observations collected from 782 weather stations in China in the T0(1981–2010) period, and the Intergovernmental Panel on Climate Change Coupled Model Intercomparison Project(IPCC CMIP5) RCP2.6, RCP4.5, and RCP8.5 climate scenario data in the T1(2011–2040), T2(2041–2070), and T3(2071–2100) periods, the spatial distribution of ETZs and their response to climate scenarios in China were simulated in the four periods of T0, T1, T2, and T3. Additionally, a spatial shift of mean center model was developed to quantitatively calculate the shift direction and distance of each ETZ type during the periods from T0 to T3. The simulated results revealed 41 ETZ types in China, accounting for 18% of the whole land area. Cold temperate grassland/humid forest and warm temperate arid forest(564,238.5 km~2), cold temperate humid forest and warm temperate arid/humid forest(566,549.75 km~2), and north humid/humid forest and cold temperate humid forest(525,750.25 km~2) were the main ETZ types, accounting for 35% of the total ETZ area in China. Between 2010 and 2100, the area of cold temperate desert shrub and warm temperate desert shrub/thorn steppe ETZs were projected to increase at a rate of 4% per decade, which represented an increase of 3604.2, 10063.1, and 17,242 km~2 per decade under the RCP2.6, RCP4.5, and RCP8.5 scenarios, respectively. The cold ETZ was projected to transform to the warm humid ETZ in the future. The average shift distance of the mean center in the north wet forest and cold temperate desert shrub/thorn grassland ETZs was generally larger than that of other ETZs, with the mean center moving to the northeast and the shift distance being more than 150 km during the periods from T0 to T3.In addition, with a gradual increase of temperature and precipitation, the ETZs in northern China displayed a shifting northward trend, while the area of ETZs in southern China decreased gradually, and their mean center moved to high-altitude areas. The effects of climate change on ETZs presented an increasing trend in China, especially in the Qinghai-Tibet Plateau. 相似文献
3.
Dual factors of climate and human on the hydrological process are reflected not only in changes in the spatiotemporal distribution of water resource amounts but also in the various characteristics of river flow regimes. Isolating and quantifying their contributions to these hydrological alterations helps us to comprehensively understand the response mechanism and patterns of hydrological process to the two kinds of factors. Here we develop a general framework using hydrological model and 33 indicators to describe hydrological process and quantify the impact from climate and human. And we select the Upper Minjiang River(UMR) as a case to explore its feasibility. The results indicate that our approach successfully recognizes the characteristics of river flow regimes in different scenarios and quantitatively separates the climate and human contributions to multi-dimensional hydrological alterations. Among these indicators, 26 of 33 indicators decrease over the past half-century(1961–2012) in the UMR, with change rates ranging from 1.3% to 33.2%, and the human impacts are the dominant factor affecting hydrological processes, with an average relative contribution rate of 58.6%. Climate change causes an increase in most indicators, with an average relative contribution rate of 41.4%. Specifically, changes in precipitation and reservoir operation may play a considerable role in inducing these alterations. The findings in this study help us better understand the response mechanism of hydrological process under changing environment and is conducive to climate change adaptation, water resource planning and ecological construction. 相似文献
4.
《地理学报(英文版)》2019,(4)
Lateral migration of the Bhagirathi River temporally creates unavoidable geomorphic hazards in West Bengal, India. The Bhagirathi River flows SW for ～67.30 km between the confluence point of Ajay and Jalangi rivers in East Burdwan and Nadia districts of West Bengal. The course of Bhagirathi is notably migration prone and cultivates problematic changes along its course over time. In the study, we have looked into its migration tendency and unpredictability for past 238 years and then predicted the lateral shifting of river centerline using temporal satellite imageries – Landsat-5(TM) of 1987(8, December), 1995(28, January), 2005(7, January) and LISS-IV satellite imagery(2017, 5 January);SOI Toposheet – 1968–1969(79 A/2, 79 A/3, 79 A/6 and 79 A/7) and Rennell's map of 1779. Other highlights are the quest of fluvial features, oxbow lakes, mid-channel bars, channel migration rate, meander geometry, channel sinuosity in different parts of river course and the parts that experience intensive bank erosion. The entire river course has been subdivided into three segments; viz. reaches A, B and C. Investigation displays that degree of sinuosity decreases from its anterior course(1968) to the existing course(2017). Reach-specific outputs display that reach B is highly sinuous(SI value 1.94 in 2017) and SI increases temporarily, whereas for reaches A and C it decreases with time. The rate of migration is higher in reach B than that in reaches C and A. The study displays a notably decreasing trend of migration in comparison with its previous lateral migration and shows that the migration nature over time is intensively inconsistent and unpredictable except very few portions of the river course. The nature of deposition within the river channel shows an unstable behavior during the entire period of the study. Meander geometry depicts a rapid change of river course innate to meander bends and shows a higher rate of migration by meander loop cut-off rather than lateral migration that reflects the inconsistency, erosion vulnerability and unpredictable nature of migration. The present work offers a valuable source to comprehend channel changes in Bhagirathi River and serve as an efficacious base for river-bank migration and erosion hazard planning and management. 相似文献
5.
《地理学报(英文版)》2019,(1)
Glaciers and snow are major constituents of solid water bodies in mountains; they can regulate the stability of local water sources. However, they are strongly affected by climate change. This study focused on the Tianshan Mountains, using glacier and snow datasets to analyse variations in glaciers, snow, water storage, and runoff. Three typical river basins(Aksu, Kaidou, and Urumqi Rivers) were selected to interpret the impacts of glacier and snow changes on regional water resources in the Tianshan Mountains. The results exhibited a nonlinear functional relationship between glacial retreat rate and area, demonstrating that small glacial retreat is more sensitive under climate change. Further, the glacial retreat rate at the low-middle elevation zone was seen to be faster than that at the high elevation zone. The regional average terrestrial water storage(TWS) decrease rate in the Tianshan Mountains was –0.7±1.53 cm/a during 2003–2015. The highest TWS deficit region was located in the central part of the Tianshan Mountains, which was closely related to sharp glacial retreats. The increases in glacier and snow meltwater led to an increase in runoff in the three typical river basins, especially that of the Aksu River(0.4×10~8 m~3/a). The decreasing and thinning of areas, and increasing equilibrium line altitude(ELV) of glaciers have been the major causes for the decrease in runoff in the three river basins since the mid-1990 s. Therefore, the results reveal the mechanisms causing the impacts of glaciers and snow reduction in mountains on regional water resources under climate change, and provide a reference for water resources management in the mountainous river basins. 相似文献
6.
The Yarlung Zangbo River (YR) is the highest great river in the world, and its basin is one of the centers of human economic activity in Tibet. Using 10 meteorological stations over the YR basin in 1961–2005, the spatial and temporal characteristics of temperature and precipitation as well as potential evapotranspiration are analyzed. The results are as follows. (1) The annual and four seasonal mean air temperature shows statistically significant increasing trend, the tendency is more significant in winter and fall. The warming in Lhasa river basin is most significant. (2) The precipitation is decreasing from the 1960s to the 1980s and increasing since the 1980s. From 1961 to 2005, the annual and four seasonal mean precipitation is increasing but not statistically significant, especially in fall and spring. The increasing precipitation rates are more pronounced in Niyangqu and Palong Zangbo river basins, the closer to the upper YR is, the less precipitation increasing rate would be. (3) The annual and four seasonal mean potential evapotranspiration has decreased, especially after the 1980s, and most of it happens in winter and spring. The decreasing trend is most significant in the middle YR and Nianchu river basin. (4) Compared with the Mt. Qomolangma region, Tibetan Plateau, China and global average, the magnitudes of warming trend over the YR basin since the 1970s exceed those areas in the same period, and compared with the Tibetan Plateau, the magnitudes of precipitation increasing and potential evapotranspiration decreasing are larger, suggesting that the YR basin is one of the most sensitive areas to global warming. 相似文献
7.
The Heihe River Basin is the second largest inland river basin in Northwest China and it is also a hotspot in arid hydrology, water resources and other aspects of researches in cold regions. In addition, the Heihe River Basin has complete landscape, moderate watershed size, and typical social ecological environmental problems. So far, there has been no detailed assessment of glaciers change information of the whole river basin. 1:50,000 topographic map data, Landsat TM/ETM+ remote sensing images and digital elevation model data were used in this research. Through integrated computer automatic interpretation and visual interpretation methods, the object-oriented image feature extraction method was applied to extract glacier outline information. Glaciers change data were derived from analysis, and the glacier variation and its response to climate change in the period 1956/1963–2007/ 2011 were also analyzed. The results show that:(1) In the period 1956/1963–2007/2011, the Heihe River Basin's glaciers had an evident retreat trend, the total area of glaciers decreased from 361.69 km2 to 231.17 km~2; shrinking at a rate of 36.08%, with average single glacier area decrease 0.14 km~2; the total number of the glaciers decreased from 967 to 800.(2) Glaciers in this basin are mainly distributed at elevations of 4300–4400 m, 4400–4500 m and 4500–4600 m; and there are significant regional differences in glaciers distribution and glaciers change.(3) Compared with other western mountain glaciers, glaciers retreat in the Heihe River Basin has a higher rate.(4) Analysis of the six meteorological stations' annual average temperature and precipitation data from 1960 to 2010 suggests that the mean annual temperature increased significantly and the annual precipitation also showed an increasing trend. It is concluded that glacier shrinkage is closely related with temperature rising, besides, glacier melting caused by rising temperatures greater than glacier mass supply by increased precipitation to some extent. 相似文献
8.
The changing pattern of the Lower Yellow River (LYR) obtained from the traditional studies, which mainly did literal analysis based on historical documents related to the LYR are too macroscopic and absent of intuitiveness. This paper integrates all the records in historical documents related to course shift, flood and overflow of the last 3000 years and stores them in a GIS database. Then, all the data will be visualized in the form of map, which is helpful to show and understand the rules those events conform more intuitively and accurately. Taking these data as foundation, this study summarizes characteristics of the LYR’s courses and influence scope, and classifies them both into three types; divides the flow directions of the LYR’s courses into two periods, and proposes its changing pattern; concludes the characteristic of diversion points of courses shift events; calculates the velocity of courses shifts, gradient and sinuosity, and analyzes their changing patterns. Finally, this study classifies factors that may influence the occurrence of a course shift into two types: the internal factors, such as sediment rate, gradient and sinuosity of the river, and the external factors, such as precipitation and human activities. 相似文献
9.
RS analysis of glaciers change in the Heihe River Basin,Northwest China,during the recent decades 总被引：2，自引：1，他引：1
Baojuan Huai Zhongqin Li Shengjie Wang Meiping Sun Ping Zhou Yan Xiao 《地理学报(英文版)》2014,24(6):993-1008
The Heihe River Basin is the second largest inland river basin in Northwest China and it is also a hotspot in arid hydrology, water resources and other aspects of researches in cold regions. In addition, the Heihe River Basin has complete landscape, moderate watershed size, and typical social ecological environmental problems. So far, there has been no detailed assessment of glaciers change information of the whole river basin. 1：50,000 topographic map data, Landsat TM/ETM＋ remote sensing images and digital elevation model data were used in this research. Through integrated computer automatic interpretation and visual interpretation methods, the object-oriented image feature extraction method was applied to extract glacier outline information. Glaciers change data were derived from analysis, and the glacier variation and its response to climate change in the period 1956/1963–2007/ 2011 were also analyzed. The results show that：（1） In the period 1956/1963–2007/2011, the Heihe River Basin＇s glaciers had an evident retreat trend, the total area of glaciers decreased from 361.69 km2 to 231.17 km~2; shrinking at a rate of 36.08%, with average single glacier area decrease 0.14 km~2; the total number of the glaciers decreased from 967 to 800.（2） Glaciers in this basin are mainly distributed at elevations of 4300–4400 m, 4400–4500 m and 4500–4600 m; and there are significant regional differences in glaciers distribution and glaciers change.（3） Compared with other western mountain glaciers, glaciers retreat in the Heihe River Basin has a higher rate.（4） Analysis of the six meteorological stations＇ annual average temperature and precipitation data from 1960 to 2010 suggests that the mean annual temperature increased significantly and the annual precipitation also showed an increasing trend. It is concluded that glacier shrinkage is closely related with temperature rising, besides, glacier melting caused by rising temperatures greater than glacier mass supply by increased precipitation to 相似文献
10.
《地理学报(英文版)》2019,(1)
The knowledge of geomorphological evolution from an estuary to a river delta is necessary to form the formulation of comprehensive land-ocean interaction management strategies. In this study, the dominant factor controlling the geomorphological variability and the threshold sediment flux(TSF) to form a river delta in Hainan Island, southern China, including accommodation space, sediment supply, and reworking forces, was investigated by the method of big data analytics. The results indicated the 25 estuaries in consideration can be divided into three geographical groups, i.e. the multi-factors-controlled northern mixed estuaries, wave-dominated western estuaries with river deltas, and typhoon-dominated eastern coastal lagoon estuaries. For alluvial plain(AP) estuaries, the order of magnitude of TSFs is the smallest(10~1 kt·yr~(–1)), for barrier-lagoon(BL) ones is the highest(10~2 kt·yr~(–1)), and for drowned valley(DV) ones is moderate(10~2 kt·yr~(–1)). The river deltas associated with DV systems should be relatively large, and those related to BLs should be small, with the AP deltas being between the above mentioned types. The present study provides a technique to evaluate the role played by TSF for the formation of river deltas in micro-tidal and wave-dominated and typhoon-influenced coastal environments. 相似文献
11.
《地理学报(英文版)》2019,(12)
Extraction and analysis of the shoreline and land reclamation patterns are important for studies on topics such as the dynamics of coastal wetland ecological environments, transportation and exchange of material energy in coastal regions, and recruitment of fishery resources. Spatial-temporal variations in the shoreline and land reclamation in the Bohai Sea were analyzed based on 49 Landsat images of 7 periods from 1985 to 2015. The following conclusions were drawn.(1) The extracted shoreline data based on visual interpretation had high precision, and the shoreline extraction errors could be controlled within the theoretical range.(2) Over the past 30 years, the shoreline of the Bohai Sea has exhibited an average rate of change of 188.47 m/a and an average accretion distance of 3.55×10~3 m toward the sea. The fastest rate of shoreline change occurred in Laizhou Bay(134.78 m/a), followed by Bohai Bay(128.20 m/a) and Liaodong Bay(61.69 m/a).(3) The average rate of reclamation was 3.25×10~4 ha/a in the Bohai Sea, where the total area of aquaculture land, unused land, and salt land exceeded 60% of the total reclamation area.(4) The geometric shape of the bay became increasingly complicated from year to year, and the geometric center of gravity of the bay moved rapidly toward the sea. In addition, the area of the bay showed a significant decreasing trend. Therefore, to protect the function and structure of the ecosystem in coastal regions, we must control the scale and rate of land reclamation in the future. 相似文献
12.
《地理学报(英文版)》2017,(6)
China had implemented the national strategies for Major Function-oriented Zones(MFOZs)to realize the goal of national sustainable development since 2010.This study analyzed and compared spatio-temporal characteristics and differences in built-up area for China’s MFOZs using a China’s Land Use Database(CLUD)derived from high-resolution remotely sensed images in the periods of 2000–2010 and 2010–2013.To sum up:(1)The percentage of built-up area in each of the MFOZs was significantly different,revealing the gradient feature of national land development based on the distribution of the main functions.(2)Annual growth in built-up area in optimal development zones(ODZs)decreased significantly during 2010–2013 compared with the period 2000–2010,while annual growth in built-up area in key development zones(KDZs),agricultural production zones(APZs)and key ecological function zones(KEFZs)increased significantly.(3)In ODZs,the average annual increase in built-up area in the Yangtze River Delta region was significantly higher than in other regions;the average area increase and rate of increase of built-up area in KDZs was faster in the western region than in other regions;average annual area growth of built-up area in APZs in the northeast,central and western regions was twice as high as the previous decade on average;the annual rate of change and increase in the dynamic degree of built-up area were most notable in KEFZs in the central region.(4)The spatial pattern and characteristics of built-up area expansions in the period 2010–2013 reflected the gradient feature of the plan for MFOZs.But the rate of increase locally in built-up area in ODZs,APZs and KEFZs is fast,so the effective measures must be adopted in the implementation of national and regional policies.The conclusions indicated these methods and results were meaningful for future regulation strategies in optimizing national land development in China. 相似文献
13.
近60年黄河水沙变化及其对三角洲沉积的影响 总被引：1，自引：1，他引：0
In order to find out the variation process of water-sediment and its effect on the Yellow River Delta, the water discharge and sediment load at Lijin from 1950 to 2007 and the decrease of water discharge and sediment load in the Yellow River Basin caused by human disturbances were analyzed by means of statistics. It was shown that the water discharge and sediment load into the sea were decreasing from 1950 to 2007 with serious fluctuation. The human activities were the main cause for decrease of water discharge and sediment load into the sea. From 1950 to 2005, the average annual reduction of water discharge and sediment load by means of water-soil conservation practices were 2.02×109 m3 and 3.41×108 t respectively, and the average annual volume by water abstraction for industry and agriculture were 2.52×1010 m3 and 2.42×108 t respectively. The average sediment trapped by Sanmenxia Reservoir was 1.45×108 t from 1960 to 2007, and the average sediment retention of Xiaolangdi Reservoir was 2.398×108 t from 1997 to 2007. Compared to the data records at Huanyuankou, the water discharge and sediment load into the sea decreased with siltation in the lower reaches and increased with scouring in the lower reaches. The coastline near river mouth extended and the delta area increased when the ratio of accumulative sediment load and accumulative water discharge into the sea (SSCT) is 25.4–26.0 kg/m3 in different time periods. However, the sharp decrease of water discharge and sediment load into the sea in recent years, especially the Yellow River into the sea at Qing 8, the entire Yellow River Delta has turned into erosion from siltation, and the time for a reversal of the state was about 1997. 相似文献
14.
Groundwater resource is vital to the sustainable development of socio-economics in arid and semi-arid regions of Northwest China. An estimation of the groundwater resources variation in Zhangye Basin was made during 1985–2013 based on long-term groundwater observation data and geostatistical method. The results show that from 1985 to 2013, groundwater storage exhibited tremendous dissimilarity on temporal and spatial scale for the whole Zhangye Basin, especially before and after implementation of the water diversion policy. Trend of groundwater storage varied from quick to slow decline or increase. The accumulative groundwater storage decreased nearly 47.52×10~8 m~3, and annual average depletion rate reached 1.64×10~8 m~3/a. Among which, the accumulative groundwater storage of the river and well water mixed irrigation district decreased by 37.48×10~8 m~3, accounting for about 78.87% of the total groundwater depletion of the Zhangye Basin. Accumulative depletion of groundwater storage varied in respective irrigation districts. Though groundwater resources depletion rate slowed down from 2005, the overall storage in the whole basin and respective districts during 1985–2013 was still in a severe deficit such that, the groundwater resource was in a rather negative balance, which could threaten the local aquifer. This is the joint effect of climate change and human activities, however human activities, such as water diversion policy and groundwater exploitation, became increasingly intense. Our research results could provide a reasonable estimation for the groundwater balance in Zhangye Basin, providing a scientific basis for water resources unified planning and, this method can provide a relatively reliable way of estimation for large scale groundwater resources. 相似文献
15.
Theoretical difficulties for mapping and for estimating river regime characteristics in a large-scale basin remain because of the nature of the variable under study: river flows are related to a specific area, i.e. the drainage basin, and are hierarchically organized in space through the river network with upstream-downstream dependencies. Another limitation is there are not enough gauge stations in developing countries. This presentation aims at de-veloping the hydro-stochastic approach for producing choropleth maps of average annual runoff and computing mean discharge along the main river network for a large-scale basin. The approach applied to mean annual runoff is based on geostatistical interpolation proce-dures coupled with water balance and data uncertainty analyses. It is proved by an applica-tion in the upstream at Bengbu in the Huaihe River Basin, a typical large-scale basin in China. Hydro-stochasitic approach in a first step interpolates to a regular grid net and in a second step the grid values are integrated along rivers. The interpolation scheme includes a con-straint to be able to account for the lateral water balance along the rivers. Grid runoff map with 10 km × 10 km resolution and the discharge map along the river with the 1 km basic length unit are the main results in this study. This kind of statistic approach can be widely used be-cause it avoids the complexity of hydrological models and does not depend on the meteoro-logical data. 相似文献
16.
The agricultural and land policies in China are always focused on protecting its food supply and security because of the country’s large population and improved diets.The crop production guide ’Take Grain as the Key Link’ prompted peasants to plant grain on most of the agricultural land,leading to the majority of fertilizer being used in grain crops for many years in China.This situation has changed dramatically in recent years.Based on data pertaining to provincial crops sown area and fertilizer use per unit area in 1998 and 2008,the temporal and spatial variations of China’s fertilizer consumption by crops were analyzed at the provincial level,and the results are presented here.(1) Fertilizer consumption in China grew strongly in the last decade,while the growth was mainly attributable to the increase of fertilizer con-sumption by horticultural crops.The fertilizer consumption of grain crops dropped from 71.0% in 1998 to 57.8% in 2008.Thus,it is concluded that the emphasis of fertilizer consumption is shifting toward horticultural crops.(2) There were marked differences in the growth rates of fertilizer consumption from the regional point of view.The national average growth rate of fertilizer consumption was 31.9% during 1998-2008.The western and northeastern parts of the country came close to the national average,while the eastern part was lower,with an average of 13.0%,and central China was much higher(50.8%).The increase of fertilizer consumption in central and west China was higher than the other zones,which already ac-counted for 77.9% of the national total.Thus,it is concluded that the consumption emphasis of chemical fertilizer shifts toward the central and western regions.(3) The decline of fertilizer consumption by grain crops was largely due to the decrease in sown area compared with the increase by vegetable crops attributable to the enlarging sown area;the increase by orchard crops was affected by both expanding the sown area and fertilizer use per unit area. 相似文献
17.
This paper aims to compare the geochemical characteristics of loess-paleosol sequences in the upper reaches of the Hanjiang and Weihe river valleyswhich are located in the semi-humid temperate zone and humid subtropical zonerespectively. The Mituosi(MTS) profile in the upper reaches of the Hanjiang River valley and the Yaohecun(YHC) profile in the Weihe River valley were selected for this comparative research. The stratigraphic characteristicscompositionchemical weathering intensityleaching rates of Ca and Namobility of major elementsand transport features of Na and Fe were analyzed with respect to depth and compared between the two profiles. This study reached the following conclusions.(1) The composition of the loess-paleosol sequences in two regions are quite similar to the average composition of the upper continental crust(UCC)indicating that the loess in the two regions came from multiple sources and was mixed well. Thereforethe loess in the two regions is considered aeolian loess.(2) Compared with the loess-paleosol sequence in the Weihe River valleythe loess-paleosol sequence in the upper reaches of the Hanjiang River valley features a darker color; a higher chemical index of alteration(CIA) value; higher leaching rates of Na and Ca; higher migration ratio(relative to K) of AlSiMgand Na; and lower migration ratio of Fe and Ca. This evidence indicates that the loess-paleosol sequence in the humid subtropical environment experienced stronger chemical weathering intensity than the loess-paleosol sequence in the semi-humid temperate zone.(3) Both the YHC profile and MTS profile record a period of climate deterioration at 6000–5000 a BP. The period punctuated the mid-Holocene Climatic Optimum(8500–3100 a BP) in the study area. 相似文献
18.
The effect of peak shifts on the performance of a Kalman filter multicomponent analysis algorithm hasbeen investigated.A series of Gaussian test systems were employed to characterize the concentrationestimation errors and the morphology of the on-line residuals(the innovations sequence).Both forwardand reverse filters were used in the generation of the innovations sequences.It was found that thedifference between the forward and reverse innovations sequences gave an accurate indication of thedirection and magnitude of the peak shift.A series of overlapped two-component systems were alsoinvestigated.Again,a correlation between the difference innovations and the degree of the responseshift was observed.The behavior of the Katman filter in fitting the shifted fluorescence emissionspectrum of benzo[a]pyrene was also examined.The response for henzo[a]pyrene in cyclohexanesolution was compared to that obtained on the surface of a reversed phase thin layer chromatographyplate.A red shift of 4 nm was detected for the surface spectrum by observing the difference innovationssequence.This approach holds promise for correction of response shifts in multicomponent systems. 相似文献
19.
Based on data from six meteorological stations in the permafrost regions, 60 boreholes for long-term monitoring of permafrost
temperatures, and 710 hand-dug pits and shallow boreholes on the Qinghai-Tibet Plateau (QTP), the spatiotemporal variability of
permafrost degradation was closely examined in relation to the rates of changes in air, surface, and ground temperatures. The decadal
averages and increases in the mean annual air temperatures (MAATs) from 1961–2010 were the largest and most persistent
during the last century. MAATs rose by 1.3 °C, with an average increase rate of 0.03 °C/yr. The average of mean annual ground
surface temperatures (MAGSTs) increased by 1.3 °C at an average rate of 0.03 °C/yr. The rates of changes in ground temperatures
were ?0.01 to 0.07 °C/yr. The rates of changes in the depths of the permafrost table were ?1 to +10 cm/yr. The areal extent of
permafrost on the QTP shrank from about 1.50×106 km2 in 1975 to about 1.26×106 km2 in 2006. About 60% of the shrinkage in
area of permafrost occurred during the period from 1996 to 2006. Due to increasing air temperature since the late 1980s, warm
(>?1 °C) permafrost has started to degrade, and the degradation has gradually expanded to the zones of transitory (?1 to ?2 °C)
and cold (相似文献
20.
The change characteristics and trends of the regional climate in the source region of the Yellow River, and the response of runoff to climate change, are analyzed based on observational data of air temperature, precipitation, and runoff at 10 main hydrological and weather stations in the region. Our results show that a strong signal of climate shift from warm-dry to warm-humid in the western parts of northwestern China （Xinjiang） and the western Hexi Corridor of Gansu Province occurred in the late 1980s, and a same signal of climate change occurred in the mid-2000s in the source region of the Yellow River located in the eastern part of northwestern China. This climate changeover has led to a rapid increase in rainfall and stream runoff in the latter region. In most of the years since 2004 the average annual precipitation in the source region of the Yellow River has been greater than the long-term average annual value, and after 2007 the runoff measured at all of the hydrologic sections on the main channel of the Yellow River in the source region has also consistently exceeded the long-term average annual because of rainfall increase. It is difficult to determine the prospects of future climate change until additional observations and research are conducted on the rate and temporal and spatial extents of climate change in the region. Nevertheless, we predict that the climate shift from warm-dry to warm-humid in the source region of the Yellow River is very likely to be in the decadal time scale, which means a warming and rainy climate in the source region of the Yellow River will continue in the coming decades. 相似文献