25 November 1997, Volume 19 Issue 4

    

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  Variation Trends of Snow Cover Over the Tibetan Plateau and Their Relations to Temperature and Precipitation

  Ke Changqing, Li Peiji, Wang Caiping

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1997, 19(4): 289-294. https://doi.org/10.7522/j.issn.1000-0240.1997.0045

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  In this paper daily snow depth data, together with monthly average temperature and monthly total precipitation, at 60 primary weather stations from 1957 to 1990 were analysed by using ARMA(p,q)and multiple linear regressive analysis. The results show that an increasing trend of snow volume is almost omnipresent over the entire Tibetan Plateau, with some local decreasing trends. Its variation trend coincides with the recent snow accumulation increases in Antarctica and Greenland, therefore, snow cover on the Tibetan Plateau will increase with global warming. The secular trend of cold season temperature and precipitation in the Tibetan Plateau is increasing too. A significant positive correlation exists between snow cover and precipitation, but the correlation between snow cover and temperature is negative over the Tibetan Plateau. In recent 34 years, cold season temperature in the Tibetan Plateau has increased 0.51℃. Meanwhile, the annual increase rate of cold season precipitation is 1.1%, and annual accumulation of snow cover increases 1.7%. The increase of snow cover results from the increase of precipitation during the cold seasons with global warming.
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  Characteristics of δ¹⁸O in Summer Precipitation at Lhasa

  Tian Lide, Yao Tandong, Pu Jianchen, Yang Zhihong

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1997, 19(4): 295-301. https://doi.org/10.7522/j.issn.1000-0240.1997.0046

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  The oxygen isotope in precipitation collected at Lhasa Meteorological Station from 1993 to 1996 toghther with the observation by IAEA/WMO are analyzed in this paper. Precipitation concentrates mainly in the warm half year, especially in July, August and September. δ¹⁸O in summer precipitation has a clear signal of monsoon precipitation. There is no positive correlation between δ¹⁸O and temperature neither for the variation of the total precipitation samples nor for the seasonal variation, but there is a clear amount effect. The amount effect has overshadowed the temperature effect at Lhasa. This is just opposite to that of the Delingha Station in the north of the Tibetan Plateau where the effect of the southwest monsoon is quite limited.
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  Estimation of Average Mass Balance for Glaciers in a Water Shed and Its Application

  Shen Yongping, Xie Zichu, Ding Liangfu, Liu Jingshi

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1997, 19(4): 302-307. https://doi.org/10.7522/j.issn.1000-0240.1997.0047

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  Using method of statistical mechanics and maximum entrophy principle, we obtain that distributions of precipitation, mean depth and coefficient of runoff in a water shed can be described by a negative exponential function. In ahighmountainous basin, the maximum distributive area of precipitation, depth and coefficient of runoff is glacierized area. In this case, a calculation method of average mass balance for glaciers in a water shed has been suggested in this paper. We use the model to simulate the mass balance of Glacier No. 1 at the Headwaters of the Urumqi River. The result is reasonable and well precise. For recovery of mass balance, the method is employed to the Kangxiwa River Basin of Muztagh Ata-Kongur Ata, East Pamir, and-123.5 mm/a of mean mass balance during 1960～1990 is worked out. Finally, the long-term trend of mass balance, together with hydrological response to mass balance and precipitation changing in Chinese Pamir, are discussed.
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  A Grey Topology Method for Forecasting the Runoff in the Upper Reaches of the Yellow River

  Lan Yongchao, Kang Ersi, Yang Wenhua

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1997, 19(4): 308-311. https://doi.org/10.7522/j.issn.1000-0240.1997.0048

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  The Longyang Gorge Key Water Control System is located in Qinghai Province, 1688 km from the source of the Yellow River. The reservoir can hold 27.4×10⁹m³ of water. Ovre 80%～90% of the inflow rises from the upper Yellow River basin with a mean elevation more than 3000 m a.s.l. and a catchment area of 121972 km². It is significant to research the forecasting method of the runoff from the upper Yellow River basin and to predict exactly the inflow for power generation, irrigation and water application for both the middle and lower reaches of the river. In view of the above, the modelling method of grey system theory and topology forecast model are used to establish a super-long-term forecast model for predicting the annual mean inflow to the Longyang Gorge Reservoir based on the measured data in the Tangnag Hydrometric Station. The model was applyed to professional forecast of the reservoir inflow and the result is satisfactory.
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  A Simulated Weathering Experiment of Small Free Granite Blocks under Freeze-thaw Conditions

  Zhu Liping, W.B. Whalley, Wang Jiacheng

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1997, 19(4): 312-320. https://doi.org/10.7522/j.issn.1000-0240.1997.0049

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  Free granite blocks with size of 50 mm×50 mm×50 mm, which were uniaxial compressed and pre-treated to be dry, water and Na₂SO₄ solution soaked, were experienced freeze-thaw cycles of different temperature range. The temperature cycles were available in an environmental cabinet while the temperatures on the samples surface and inside 10 mm and 25 mm depth were recorded respectively. Samples′ weight and ultrasonic transfer velocity were also measured before and after experiment. The results show that, to these small free samples, there was no apparent temperature difference between the surface and inside. Rock temperature varied with freeze-thaw cycles but appeared “relative stable”when temperatures within the total range of the cycles were below 0℃. The weight loss of samples was very small, but still suggested that the biggest change occurred in the group of the water soaked samples. Ultrasonic transfer velocity, to most samples, turned to be slow, specially those cross the microfractures of the samples had more change. These suggested that the internal pore volume of the samples probably enlarged and microfractures had apparently developed during the freeze-thaw cycles.
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  A Study on the Relation Between Freezing Point and Load of Wet Soil

  Cui Guangxin, Yang Weihao, Li Yi

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1997, 19(4): 321-327. https://doi.org/10.7522/j.issn.1000-0240.1997.0050

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  Study on freezing point of four sorts of wet soil with different water and salt contents under loading ranging form 0 to 20 MPa are presented in this paper Experiments for studying freezing point changing with salt content and load were carried out Except for unsaturated sand, the relationship between freezing point and load obeys Clapeyron equation, and the more the salt content in soils is, the lower the freezing point of the soil is. The interaction of salt content and load has little effect on freezing point Quantitative relationships between freezing point of wet soil and load, water content and salt content are obtained.
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  Effect of Seasonal Freezing on Soil Moisture and Its Significance for Agriculture

  Gong Jiadong, Qi Xusheng, Xie Zhongkui, Wang Yajun

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1997, 19(4): 328-333. https://doi.org/10.7522/j.issn.1000-0240.1997.0051

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  Soil moisture increases due to freezing because of water migration caused by water potential of frozen soil fringe. However, increase amount depends on the moisture distribution in the soil profile before freezing. According to an experiment conducted in field, in connection with mention above, it is suggested that the time for water-storing irrigation can move up to the last ten-day period of September or the middle of October, the amount of water supplying can reduce to 60 m³/mu even to 40 m³/mu, and having a soil cover after water-storing irrigation can improve the soil moisture content in spite of earlier irrigation and lower water supplying, increasing crop emergence rate.
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  A Preliminary Simulation Experiment on Regeneration Mechanisms of Gold Placers in Permafrost

  Zhang Baolin, Wang Chunhe, Wang Jiacheng, Zhang Lixin, Tao Zhaoxiang, Gu Tongxin

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1997, 19(4): 334-339. https://doi.org/10.7522/j.issn.1000-0240.1997.0052

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  The regeneration mechanisms of gold placers in permafrost is an international pioneering issue. For the first time, this paper presents the dynamic characteristics of Au(Ⅲ), Au(0)contents and salinity in different valence gold-bearing NaCl solutions under uniaxial freezing. During the freezing, salting out makes gold and saline ions greatly migrate and richen in the unfrozen liquid, Au(Ⅲ)is stable, but Au(0)is unstable and easy to precipitate under the temperature higher than or equal to the melting point. The simulation experiment shows that the key to the regeneration of gold placers in permafrost maybe is to change the gold valence, which is affected by cold region environment, and then to accelerate the precipitation of gold in unfrozen liquid. In addition, cold environment can enrich the minute and fine gold grains in sediments and is favourable to their growth Consequently, enrichment area of gold forms in permafrost. Frost probably plays an important role in the regeneration process of gold placers in permafrost.
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  Experimental Study on the Effect of the Sample Size on Fracture Toughnees K_Ic of Frozen Soils

  Li Hongsheng, Zhu Yuanlin, Liu Zengli, Liang Chengji, Zhang Bing

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1997, 19(4): 340-345. https://doi.org/10.7522/j.issn.1000-0240.1997.0053

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  The 3-point bending tests were carried out on the frozen soil samples with different sizes so as to investigate the effect of sample size on the fracture toughness K_Ic of frozen soils. The effect coeficient α was obtained from the test results according to Weibull′s statistical theory of brittle failure, which was used to predict the theoretical values of K_Ic for the frozen soil samples. Comparisons between the theoretically calculated and measrued values of K_Ic indicated that the maximum error is less that 5%.
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  Experimental Researches on Expansion Behaviors of Saline Soil with NaCl and Na₂SO₄ Solutions

  Gao Minhuan, Li Bin, Jin Yingchun

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1997, 19(4): 346-353. https://doi.org/10.7522/j.issn.1000-0240.1997.0054

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  In this paper, based on experiments, salt expansion and its influencing factors for soil with Na₂SO₄ and NaCl are systematically studied. Some salt expansion relations are obtained, such as relation of salt expansion to temperature changing, relation of expansion starting temperature to influencing factors, relations of the range of salt expansion rapidly changing to concentration of Na₂SO₄, relation of salt expansion to cooling rate, relation of salt expansion to shaping temperature etc. The effects of Na₂SO₄ solution, NaCl solution, Cl^- /SO₄^2- and water content on salt expansion are analysed and Corresponding formulas are put foward.
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  Study on Using Short Cone Pile to Improve Frost Heaving and thaw Settlement of Soil

  Xu Xueyan, Zhang Peizhu, An Ying

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1997, 19(4): 354-358. https://doi.org/10.7522/j.issn.1000-0240.1997.0055

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  Short cone pile has a retional shape and the advantage of both the frictional pile and the upright loading pile. It can increase the bearing capacity per unit volume by 0.5～2.5 times, and the cost of foundation can be decreased by 40%～60% At the same time, it can reduce frost heaving and thaw settlement of soil, favourable to the stability of foundation. The improvement has something to do with the taper of a cone pile. The reasonable taper is between 5° and 15° Formula for calculating bearing capacity and its difference with experiment are presented in this paper, together with its management.
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  Slide Accelerated by Water Entrapment Due to Seasonal Freezing

  Wu Weijiang

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1997, 19(4): 359-365. https://doi.org/10.7522/j.issn.1000-0240.1997.0056

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  It is pointed out that effect of water entrapment due to seasonal freezing can enrich groundwater, expand the range of softening soil and enhance static and dynamic water pressures in soil. This is found from a comprehensive analysis on the occurring time of landslide and the deformation mechanisms of dangerous slope. It is an important external dynamic factor for landslides occurring in Northwest China Besides, the occurring conditions and mechanisms of this landslide are also discussed in this paper.
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  A Study on the Quaternary Glacial Relics in the Gongwang Mountains in the Northeast Part of Yunnan Province

  Kuang Mingsheng, Li Jijun, Zhao Yu, Chen Xunqian, Zhang Yaping, Guo Tianxiong

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1997, 19(4): 366-372. https://doi.org/10.7522/j.issn.1000-0240.1997.0057

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  Two Quaternary Glaciations were distinguished, and many typical glacial landforms were found mainly over two alpine areas, Jiaozhishan and Yaojintang-Niudongping, above 3100 m a s l in the Gongwang Mountains. The glacial landforms were mainly cirque, glacial rock basin and flank moraine, showing alpine cirque glaciers had occurred. According to the forming sequence and scattered feature of the glacial landforms, the Quaternary Glaciation should be separated into two periods: Last Glaciation(including Late Glaciation and Last Glacial Maximum); Penultimate Glaciation.
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  Insoluble Microparticles in the Cores and Their Climatic and Environmental Implications

  Xie Shucheng, Yao Tandong

  JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY. 1997, 19(4): 373-377. https://doi.org/10.7522/j.issn.1000-0240.1997.0058

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  This paper mainly discusses insoluble microparticles in ice cores Emphasis is laid on the development about the insoluble microparticle studies in timing, recording climatic and environmental changes, reflecting human activities and estimating background aerosols Studies in the future will focus on the insoluble microparticles in the tropical and temperate areas Organic matter, cosmic dust, chemical and mineral components of the microparticles will be paid attention to.