The change of glaciers in the Yarkant River basin in China from 1968-2009 were analyzed on the basis of the outcome of Investigation of Chinese Glacier Resources and Their Changes and result of the First Glacier Inventory of China.The result showed that the glacierized area in the Yarkant River basin have shrunk 927 km2 at a rate of 0.36%·a-1 as a whole. Compared with glacier changes in other mountains in China, the degree of retreat in the Yarkant River basin is in the medium range. The glacier shrinkage is different, depending on glacier size. Small glaciers shrink sharply even disappeared, but larger ones less change. In addition, some glaciers have surged. The glacier retreat has difference in direction, larger for southward ones and smaller for westward ones. Most glaciers are located in altitudes ranging from 5 100 to 5 500 m and from 5 500 to 5 900 m; most remarkably shrinking glaciers are located in altitudes ranging from 4 700 to 5 100 m. Most disappeared glaciers are small ones, 0.2-0.5 km2 in area, of which most are on the northeast slopes. In the research area, most disintegrated glaciers are dendritic glaciers. In the Karakoram Mountains, due to advancing and surging, there are 13 glaciers superimposed to be 6 glaciers in the research area. The air temperature and precipitation had increased from 1968 to 2009; increase in precipitation had relieved glacier retreat under a rising temperature.
Based on daily data from conventional meteorological stations from 1962 to 2012, the grades of various meteorological elements were divided and the probabilities of each grade were calculated by using fuzzy information distribution method when low temperature, snow and freezing weather appeared, which contributed to establish low temperature, snow and freezing comprehensive assessment indexes and made further efforts to provide risk zoning in southern China. The results show that the comprehensive meteorological threshold condition can be used to assess low temperature, snow and freezing events' frequency and strength reasonably when the event displayed as daily maximum temperature less than or equal to 6 ℃, daily minimum temperature less than or equal to 0 ℃, relative humidity greater than or equal to 80%, and sunshine hours less than or equal to 1.3 hours. South-central part of Sichuan, northeast corner of Yunnan, west of Guizhou, east of Hunan, north of Jiangxi, Anhui, most areas of Hubei and parts of Shaanxi Province exhibit the highest level of risk for occurring low temperature, snow and freezing weather. Although the risk of low temperature, snow and freezing weather in southern China has decreased in the past 51 years, the probability of major hazards has increased in recent ten years.
The source regions of the Datong River are located in the mid-east part of the Qilian Mountains with alpine permafrost. The characteristics and changing tendency of the permafrost were analyzed by using data from boreholes and surface observation. Regression analysis indicates that the mean annual ground temperature of permafrost in the source regions decreases with altitude with a gradient of about 3.82 ℃·km-1. The mean annual ground temperature within the permafrost is affected by surface condition closely. The permafrost depth in the source regions is also significantly dependent on altitude. With the rising of elevation by 100 m, the thickness of permafrost increases about 10 m. In the plain areas, the depth of permafrost is ranging from 17 to 86 m.Active layer thickness is closely related to local factors, especially land cover condition.There is no clearly zonality relationship between active layer thickness and altitude. Under the impact of rising temperature and human activities, permafrost in the source regions is overall in the state of degradation, and the mean annual ground temperature is increasing at a rate of about 0.0075 ℃·a-1.
Snow surface albedo plays an important role in the radiation budget and global climate models. In this paper, the observed albedo data are used to calculate the surface albedo as the true value to validate the albedo derived from TM/ETM+ image at 30 m, then the TM/ETM+ albedo is aggregated to 500 m resolution and compared with the MOD10A1 snow albedo daily (SAD). The results show that MODIS SAD products do not reflect snow albedo very well over mountains. However, the overall absolute error, standard deviation for the MODIS SAD products is 0.0548 and 0.0727, respectively, so it still can be used to study the snow cover change. A method for estimating snow albedo under cloud is developed. By using the MOD10A1 SAD and AMSR-E snow water equivalent (SWE) products, the snow under cloud is recognized, then use the SWE and Nash LSM snow albedo model to estimate the snow albedo under cloud. We can use this method to produce MODIS daily cloudless snow albedo product. The observed albedo data are used to validate the accuracy of the new SAD product. There is a relatively consistency between the MODIS SAD products after cloud removal and the observed ones, with an overall absolute error of 0.078.
To improve the understanding on response mechanism of the vulnerable ecological system on the Tibetan Plateau to the climatic change, relationship between alpine grassland vegetation index and ground surface temperature from 1982 to 2006 is investigated over the Tibetan Plateau. The data resources are ground surface temperature (GST) data from meteorological stations and relative cell NDVI values quoted from the GIMMS NDVI database. Employing regression analysis method, correlations between alpine grassland' NDVI and GST by various time-scale and the annual changes both of them are focused on. The results show that both of alpine grassland NDVI and GST showed positive trend from 1982 to 2006 overall the plateau. The trend of annual mean NDVI, NDVI in growing season, maximum NDVI and annual mean GST, GST in growing season were 0.007, 0.011, 0.007 per decade and 0.60, 0.43 degrees Celsius per decade, respectively. The area of maximum NDVI associated with GST accounted for 70.49%. However, spacial heterogeneity in topography, climatic condition and hydrological condition led the complexity in the impact of GST to the growth of grass. The correlation between maximum NDVI and annual mean GST was found to be most significant; in reviving and withering period, NDVI and GST were significantly positively correlated. The correlation of the maximum NDVI to the GST clearly depended on bio-coverage:they briefly negative correlated for poor vegetation cover or degrading regions; but positive for the good vegetation cover.
As the special ecotone from the closed forest line to the tree limit in alpine zone, timberline is highly vulnerable to climate change, and the trees near the timberline are very sensitive to environmental change. Sabina przewalskii is the dominant tree species in alpine ecosystems in the northeast Tibetan Plateau, mainly distributed at dry south-facing and infertile slopes. To test the response patterns of the leaf functional traits in Sabina przewalskii along the environmental gradient near the alpine timberline, the following items were measured:leaf dry matter content (LDMC), leaf mass per unit area (LMA), leaf stable carbon isotope composition (δ13C), leaf carbon content per unit mass (Cmass), leaf nitrogen content per unit mass (Nmass), leaf carbon-nitrogen ratio (C/N), leaf free water content (FW) and the ratio of leaf free water content and leaf bound water content (FW/BW) in Sabina przewalskii on the west-facing and east-facing slopes near timberline of the Qaidam Basin in the northeast Tibetan Plateau. It is found that Nmass, FW and FW/BW of Sabina przewalskii located in the sites of treeline and tree species line were higher than that in the sites of closed forest, while that of LDMC and C/N showed the opposite patterns, even LMA, δ13C and Cmass had no remarkable changes in near timberline of both west-facing and east-facing slopes. Meanwhile, LMA only changed significantly near timberline in west-facing slope. In addition, FW was positively related with LDMC and Nmass, and negatively related with FW/BW. Negative relationships between LMA and Cmass, Nmass and C/N were also found. Overall, these results indicated that Sabina przewalskii as a drought and cold tolerant native tree species in the alpine ecosystem mainly accommodates the harsh environment by the way of higher leaf free water content, photosynthetic capacity and some nitrogenous compounds.
Nocturnal sap flow has ecological and physiological significant for plants, and it is part of plant water that cannot be ignored. The variations of Picea crassifolia nocturnal sap flows in different weather conditions and their responses to meteorological factors and tree size in the Qilian Mountains are analyzed, in order to have a better understanding of the transpiration of Picea crassifolia. During June 12 to October 16, 2011, sap flow velocities of seven Picea crassifolia trees were measured continuously by SF-300 heat pulse meters. Microclimate data were collected synchronously by two automatic weather stations in Pailugou watershed. The nocturnal sap flow velocity was measured from (2.78±0.64) g·cm-2·h-1 to (5.02±1.06) g·cm-2·h-1 in typical sunny days and from (2.31±0.62) to (3.94±1.22) g·cm-2·h-1 in typical cloudy days, with the average values of (3.55±0.28) g·cm-2·h-1 and (3.06±0.24) g·cm-2·h-1, respectively. Nocturnal sap flow is (34.51±6.20) % of the total daily flow in typical sunny days and (46.06±11.20) % of that in typical cloudy days. Nocturnal sap velocity is significantly correlated with vapor pressure deficit and temperature, and insignificantly correlated with wind speed. Nocturnal sap flow has linear relationships with diameter at the breast height, tree height, sapwood area, product of tree height and the square of diameter at the breast height, respectively. But nocturnal sap flow is insignificantly related with crown size. In conclusion, the variation of nocturnal sap flow of Picea crassifolia is controlled by its physiological characteristics and the environmental factors. Nocturnal sap flow of Picea crassifolia is used for transpiration and water recharge.
Mineral assemblages in lake sediments are sensitive indicators of palaeoclimates, whose types anddeposit processes have important significances to interpretations of mineralogical proxies.The ubiquitous inverse correlation between saline minerals and detrital minerals in the Late Quaternary lake sediments has disturbed the interpretation and application of mineral assemblages as a paleoclimate proxy. A correct understanding of the relationship from the perspective of earth sciences can provide important scientific basis for hydrodynamics of lake and quantitative research of palaeoclimate. In this paper,five sections from different positions of Zhuye Lake (Sections QTH01, QTH02, XQ, SKJ and JTL) were chosen to conduct a comparative study on saline mineral contents and grain sizes in order to make clear the sedimentary models of saline minerals and detrital mineralsunder different hydrodynamic conditions. The results revealed that in the aeolian layers, sediments above 200 μm mainly are aeolian sands from the Badain Jaran Desert and the Tengger Desert. In lake sediments, wind force slightly contributes to the deposition of silt between 20 μm and 70 μm, but silt and sand under 200 μm are dominated by hydrodynamic effect, and carbonate mineral enriches in this grain size interval. Meanwhile, sedimentary processes of saline mineral show different patterns under different sedimentary conditions. Sedimentary environment at Sections QTH01 and QTH02 was stationary, and carbonate content was significantly high; Section XQ had strong hydrodynamic condition. At the same time, Sections SKJ and JTL were far away from the estuary, and carbonate content was relatively low. Sedimentary environment at Sections QTH01, QTH02 and XQ were dominated by runoff, where there was high value of carbonate content in the lake sediments corresponding to a finer average grain size; Sections SKJ and JTL were influenced by local environment, so the high value of carbonate content was corresponding to coarse particles. Above all, saline mineral contents in lake sediments of arid areas were closely related to the sedimentary process; therefore, the application of the saline minerals in global change research should be established on the basis of the full study of the sedimentary dynamic mechanism.
General embankment and embankment with heat insulating material on the Qinghai-Tibet Railway are proved to be thermal instable in warmer permafrost regions, so, effective reinforcement with crushed rock slope protection and thermosyphon is urgent. The practical effect of the implement of protect underlying permafrost is a matter of great public interest. Therefore, thermal state of the embankments in warmer and ice-rich permafrost regions in Beiluhe after crushed rock slope protection coupled with thermosyphon is investigated. The results indicated that (1) when the general embankment is reinforced with crushed rock slope protection coupled with thermosyphon, artificial permafrost table further uplifts, and ground temperature under both the left and the right shoulder decreases distinctly, with a tendency that the temperature field is getting more and more symmetry. What's more, the temperature decreasing range is enlarging and extending downwards. However, ground temperature in the deeper layer under the central embankment is still increasing, with a diminishing increasing rate; (2) when the heat insulating embankment reinforced with crushed rock slope protection coupled with thermosyphon, artificial permafrost table is further uplifting to the vicinity of the insulating layer; besides, residual thawed layer disappears and ground temperature under the central embankment begins to decrease after two frozen-thaw cycles. Thus, reinforcement of crushed rock slope protection coupled with thermosyphon plays an active role in controlling the ground temperature within the embankment and the permafrost beneath.
Based on the data of ground temperature and deformation beneath embankment of the Qinghai-Tibet Railway in permafrost regions from 2006 to 2013, characteristics of thawed interlayer beneath embankment and its effect on the embankment settlement deformation are studied. The results indicate that there is a little thawed interlayers beneath the original field along the Qinghai-Tibet Railway. However, beneath the embankment the thawed interlayer develops widely, while it can be refrozen totally in the regions of lower annual mean ground temperature and developed further in the regions of higher annual mean ground temperature. Thawed interlayer is closely related to the embankment settlement deformation. The ice content of permafrost under the thawed interlayer controls the settlement deformation of the embankment; the higher the ice content is, the more the settlement deformation is.
Freezing-thawing cycles have different effects on the structures of different soils. The impact of freezing-thawing cycles on the micro-structure of soil is studied, considering that the three-phase composition of soil is fundamental to the phase change of water and moisture migration among soil particles. The change of proportions of three-phase components and their forms due to freezing-thawing cycles result in the changes in the structures of soil particles. In the paper, the main components in a soil structure system are discussed. A parameter, which is defined as "Structural Potential of Freezing-Thawing", is proposed to quantitatively describe the key components change in the soil fabrics. The degree of the soil damage can be mathematically estimated by the rate of key component change in soil structures due to freezing-thawing cycles.
Aeolian sand has damaged the Qinghai-Tibet Railway. In this study, the impact of aeolian sand on cooling effect of crushed-rock embankment of Qinghai-Tibet Railway is investigated on the basis of a coupled mathematical model of convective heat transfer and heat conduction with phase change. In addition, climate warming is also considered. The results show that extensive convection can be produced in the layer of block-stone for open block-stone embankment. After the crushed-rock layer filled with aeolian sand, it is clear that the cooling effect of crushed-rock embankment will drop off, which can be seen by analyzing velocity variation in the rock layer, then permafrost table will rise gradually. The cooling mechanisms of the closed embankment significantly depend on natural convection. The artificial permafrost table beneath the center of embankment is higher than that of the adjacent regions due to the impact of filling soil. After the surface of closed rock layer buried by aeolian sand, natural convection intensity weakens gradually. In addition, the cooling effect of rock layer can counteract the negative effect of climate warming and can uplift the permafrost table. The results can provide a guide for the infrastructure design and reinforcing Qinghai-Tibet Railway in permafrost regions.
With the increasing of sandy desertification in alpine regions of China, the scope and intensity of the influence of aeolian sand accumulation on permafrost grows bigger and bigger. However, this situation is not clear so far, especially lack of laboratory experimental study. In this paper, the influence of aeolian sand accumulation with different thickness on permafrost temperature is researched through laboratory experiment. The results show that except for the air temperature transition periods, While the air temperature is negative, the frozen soil temperatures at upper-middle layer covered by sand are higher than that without sand cover. The thicker the sand layer is, the higher the frozen soil temperature is. When all of the frozen soil temperatures are negative, the soil is always in frozen state during this period. When the air temperature is positive, the frozen soil temperatures at upper-middle layer covered with sand layer are lower than that without sand cover. The thicker the sand layer is, the lower the frozen soil temperature is. While warm season is the thawing period for frozen soil, so the cooling effect of sand layer could delay the thawing process in this phase. The mean temperature at the bottom of frozen soil covered with sand layer is lower than that without sand cover during the whole three cycles. The thicker the sand layer is, the smaller the temperature amplitude at the bottom of frozen soil is.
The remolded loess from Fuping, a county of Shaanxi Province, was taken as the object of study, and variable quantity and variable coefficients were introduced to describe clear the physical properties. It is found that the variable quantity of the density of the loess change almost in the opposite way of that of void ratio. The changing quantities of Atterberg limits become smaller with increase in freezing-thawing cycles; the variable coefficient decreases with increase in freezing-thawing cycles, suggesting that new structures are going to form within the soil and become stable. Based on the variability analysis of the basic physical properties of the loess, it is possible to further discuss the transform in internal particle arrangement, granulometric composition and mineral composition. This research is useful for solving the geotechnical problems of loess under the freezing-thawing cycles in the regions. At the same time, it is also one of the fundamental methods for judging the engineering properties of the loess.
Freezing-thawing is a kind of weathering process, which considerably changes structures of soil. Change in soil pore structures has given expression to change in structure characteristics. In order to study the influence of freezing-thawing cycles on pore structures, specimens of silty clay from the Tibetan Plateau were prepared for tests under freezing-thawing cycles, 50 at most. Mercury intrusion porosimetry (MIP) is used to obtain pore size distribution and pore fractal dimension. A bimodal pattern is found the log-differential curves, which indicates that two different mechanisms are involved in forming the pores within the material. Freezing-thawing cycles have less impact on pores of small size, because of the pore size and pore volume almost remaining unchanged. However, pores of large size (especially the pore size at 20-40 μm) are influenced greatly by freezing-thawing cycles for the pore size and pore volume greatly increased. There is no obvious relation between soil porosity and freezing-thawing cycles. However, the overall changing trend of the soil porosity is first increasing and then decreasing. According to a pore fractal dimension calculation, freezing-thawing cycles change the pore structures, resulting in decrease in pore wall roughness and pore structure complexity.
Based on the method of moving mesh, a heat transfer finite element numerical model with phase change under cylindrical system was presented. The thermal change and morphologic process of thermokarst lakes were investigated. The results showed that the thermokarst lake expanded at a linear rate of 0.7 m·a-1. The depth of the lake increased with the thawing of ice-rich permafrost. The increasing rate in depth was slow at first, then it became fast, finally it kept constant. The process of expansion and the settlement of the lake was significant during the period of May to Jan. next year, while they were suspended from Feb. to May. The scope of thermal effect increased gradually in the moving boundary model, while it increased firstly and then kept constant in the fixed boundary model. The results showed that the fixed boundary model may overestimate the thermal effect on permafrost under the thermokarst lake and underestimate the thermal effect on permafrost far from the lake.
Both field and laboratory tests showed that frost heaving susceptibility of coarse grained soil were related to many factors, such as soil gradation, initial moisture content, temperature and external loads. Apparent frost heaving had been observed in coarse grained soil under certain composition conditions. In an attempt to explain the subgrade frost heaving properties of Harbin-Dalian high-speed railway, based on some documents on frost heaving properties of coarse grained soil, in this paper, first, frost heaving theory of coarse grained soil is disserted and reviewed, then research findings and problems about fines, water, and temperature, which influence frost heaving properties of coarse grained soil seriously, are presented. At last, several issues on frost heaving theory and model are proposed, which should be paid more attention to, in order to evaluate and prevent frost heaving of highway and railway better.
Due to the influences of complex mountainous topography, the spatial-temporal characteristics of water and energy fluxes in a mountainous river basin are often dramatically changed. In this paper, a macro scale hydrologic model, the variable infiltration capacity (VIC) model, was used to simulate the spatial-temporal distribution of water and energy fluxes in the upper reaches of the Heihe River. The simulated results were validated with in-situ observations. It was showed that the VIC model is able to properly simulate the outlet discharge and net solar radiation, while it could only represent the changing trends of other variables, such as sensible heat flux, latent heat flux and ground heat flux. The simulated snow process differed from observations, leading to underestimation of outlet runoff, a sudden rise in soil moisture around April and a discrepancy in energy fluxes simulation. The VIC model has a good simulation of soil moisture in summer (from June to September), but bad in other months in which snow melting and soil thawing/freezing processes occur. Snow melting while top soil thawing will jointly induce a sudden rise in soil moisture, and top soil freezing will induce a fast drop in soil moisture. Overall, the VIC model is capable of simulating the spatial-temporal distribution of water and energy fluxes in mountainous basins with spaces to be improved where snow melt and soil thawing/freezing take place.
As water resources, flood caused by meltwater from snow cover and glacier is the important sources to supply glacial runoff and the lifeblood, without which the oasis agriculture in dry regions in West China cannot survive and develop. The topography of Xinjiang is various and complicated, with high mountains and steep slopes mostly in mountainous regions, where rivers gather water fast, flood easy takes place and water conservancy facilities are relatively poor. Therefore, disasters such as glacier flood and snowmelt flood become a potent threat to the local residents and important defense line's safe operation. Under the general background of global warming, the frequency of flood disasters is increasing in Xinjiang, especially meltwater flood from snow cover and glacier. This situation will cause a serious loss to people's lives and property and other facilities, such as traffic lines, reservoirs and channels. Thus, it is more important to discuss the predictability of these disasters. In this paper, using the snowmelt flood data in Xinjiang from 2001 to 2012, the resent characteristics of temporal and spatial distribution of snowmelt flood in Xinjiang is analyzed. The results indicate that the snowmelt flood is correlated with precipitation from early Oct. to Mar. in Xinjiang. In the year of more precipitation, the snowmelt flood is more frequent in correspondingly. Basically, the snowmelt flood occurs in the order from west to east and from south to north in northern Xinjiang, while from west to east and from north to south in southern Xinjiang. Temporally, the snowmelt flood in Xinjiang mostly appears in spring and summer. In northern Xinjiang it occurs more frequently in March, but in southern Xinjiang it occurs more frequently in July. The Ili, Changji, Altay and Hotan Prefectures and the Qinggil, Vrümqi, Akto, Minfeng City/County are the high-incidence areas of snowmelt flood.
The freezing-thawing process, ground temperature and moisture migration within the black soil plow layer were analyzed with the measured data of soil temperature and moisture within the black soil plow layer at the Water Conservancy Comprehensive Experimental Research Center of Heilongjiang Province on the outskirts of Harbin, Heilongjiang Province of China from November 2011 to April 2012, where a typical middle-deep seasonally frozen soil experimental observation field has been set up. In this paper, the freezing-thawing process of middle-deep seasonally frozen plow layer of black soil on shady slopes and sunny slopes are analyzed, including the characteristics of the freezing and thawing process at different depths of black soil plow layer. At different depths of the black soil plow layer, soil moisture migration and soil moisture change with precipitation at different depths are also discussed. The results show that in middle-deep seasonally frozen ground regions, black soil under the plow layer usually has a freezing-thawing period of 164 days, approximately 5.5 months, which can be divided into five stages. Stage I lasts 18 days, when the plow layer of surface black soil begins daily frozen state by day; at this stage the plow layer of black soil thawing by day and freezing at night, with a freezing-thawing cycle in every day; on the sunny slopes of plow layer of black soil, before 08:00 and after 20:00 the air temperatures is lower than soil temperature, and the air temperature is higher than the soil temperature at 14:00 at the depths of 1 cm and 5 cm; on the shady slopes of the plow layer of black soil, ground temperature at 08:00, 14:00 is lower than air temperature, and at 20:00 the air temperature is the same as ground temperature at the depth of 1 cm basically. Stage II lasts 72 days, black topsoil is in a frozen state by day, with a frozen deep going down; at the same depth of soil temperature on shady slopes is lower than that on sunny slopes. Stage III lasts 22 days, which is a soil stably frozen period, when all the frozen layer of soil presents completely frozen state; at 08:00 and 14:00 air temperature substantially exceeds soil temperature on shady slopes. Stage IV lasts 52 days, when black topsoil thaws by day and freezes at night, in an alternating state between day and night, soil freezing-thawing cycle gradually develops downwards; on sunny slopes soil thawing is deeper and earlier than that on shady slopes; on shady slopes topsoil experiences 47 freeze-thaw cycles, and on sunny slopes it is 39. Stage V is a stably thawing period, when alternate freezing and thawing does not present in the thawing process until the frozen layer entirely thawed. In the seasonally frozen ground regions of black soil plow layer, soil temperature continuous curve functional forms of expression are in line with cyclical fluctuations in ground temperature equations. After the whole period of freezing and thawing, soil moisture content on shady slopes and sunny slopes of black soil plow layer is greater than that before freezing. The black soil plow layer soil moisture on shady slope is significantly lower than that on sunny slope. On the sunny slopes, within the black soil plow layer the maximum depth of soil moisture is at the depth of 5 cm in the whole period of soil freezing and thawing cycles. On the shady slopes, soil moisture change within black soil plow layer is not obvious. But on shady slope, within black soil plow layer topsoil moisture changes less at the depth of 1 cm, 5 cm and 10 cm, which significantly dependents on precipitation in the thawing period. Again, soil temperature change will affect the soil moisture content variation in seasonally frozen ground regions with topsoil black soil freezing and thawing cycles.
Evapotranspiration (ET) plays an important role in water balance. However, there is a great difficulty to get long-term records of ET by field observations in high-cold mountainous regions, resulting in lack of understanding the ET of alpine meadow, in spite of the meadow covering a large of area in high-cold mountains. Weighing microlysimeter method had been used to gain the ET of alpine meadow in the upper reaches of the Aksu River. Measurement revealed that the total ET of the alpine meadow was 511.3 mm, and the daily average was 1.4 mm·d-1. The value of ET varies significantly with season. The values of ET in freezing stage, early growing stage, growing stage, last growing stage were 53.9, 41.0, 363.8 and 52.6 mm, respectively, and their proportions occupy 10.5%, 8.0%, 71.2% and 10.3% of the annual ET values respectively. In this paper, it is also discussed that the applicability of the least squares support vector machine (LS-SVM) in estimation of the actual ET in alpine meadow. The results showed that LS-SVM can better estimate actual ET with high accuracy, which will be a good and useful method for estimating actual ET in the high-cold mountainous regions.
Using the isotope enabled atmospheric water balance model (iAWBM), the temporal variations of δ18O in atmospheric vapor and in precipitation are simulated and compared with actual observed data at Changsha station located in East Asian monsoon regions, in order to examine the capability of iAWBM simulating the water isotope cycle in atmosphere in monsoon regions, to deal with the main causes of isotope effects and to improve the understanding of isotope effects in the water cycle in monsoon regions. The simulated results reproduce well the observed seasonal variations of δ18O in precipitation. The basic characteristics that the stable isotopes in precipitation are depleted during the rainy season and enriched during the drought season, and the observed amount effect are well simulated under daily time scale. The simulated weighted average -6.58‰, of δ18O in precipitation during prevailing winter monsoon, is almost the same as actual one in the same period, but the value -9.58‰ during prevailing summer monsoon is lower than the actual one in the same period, from January, 2010 to December, 2012. As the designed, four forcing variables, atmospheric precipitable water, vapor flux, evaporation and precipitation, are combined into iAWBM for simulating the stable water isotope cycle. Of these four variables, the impact of precipitable water on the variation of stable water isotopes is embodied in the other three variables. Vapor flux has dual roles of enriching and depleting stable isotopes in vapor. Evaporation and precipitation have the role of enriching and depleting stable isotopes in vapor, respectively. For two variables that have the enriching impact on stable isotopes in vapor, the average isotopic contribution amount from vapor flux is 1.66‰ with the average contribution rate of 63.97%, and that from evaporation is 0.91‰ with the average contribution rate of 36.03%, showing that the isotopic contribution of vapor flux plays a major role. For two variables that have the depleting impact on stable isotopes in vapor, the average isotopic contribution amount from vapor flux is -1.40‰ with the average contribution rate of 53.47%, and that from precipitation is -1.09‰ with the average contribution rate of 46.53%, showing that the isotopic contribution of vapor flux is comparable to that of precipitation.
Environmental pollution is more and more highlighted in economic development in West China, with different influences in different provinces, as well as, different provinces affected by environmental problems of similar degree. Eleven indicators are selected to assess the environmental pollution degree of the twelve provinces in West China with the method of hierachical cluster analysis. As a result, four clusters are revealed, i.e., the first cluster (involving Guizhou, Gansu, Yunnan, Shaanxi, Guangxi and Chongqing), the second cluster (involving Inner Mongolia and Sichuan), the third cluster (involving Xizang (Tibet), Ningxia and Qinghai) and fourth cluster (Xinjiang). Therefore, to deal with the relationship between the ecological system and economic development, it is needed to coordinate with the both and to insist sustainable development.
