THE LITTLE ICE AGE OF THE NORTHWEST REGION,CHINA

The Little Ice Age began in the early 15 the century and ended in 16 the century in the northwest region of China. In the Northern Hemisphere, the age of the Little Ice Age postponed form north to south, form west to east, and moist region to drought. Judged by the data the Little Ice Age of the Northwest China is later than the eastern China and Europe. The climate of the Little Ice Age in northwest China was cold-wet. In northwest China, as compared with the Little Ice Age, the recently annual temperature have raised about 1-1.3℃, the precipitation have reduced 50-78 mm, the evaporation have increased 7%, the glacier area have reduced about 21-46%, and the runoff have reduced about 14% in the river which the meltwater supply proportion is less than 10%. To sum up, since the Little Ice Age the warm-dry tendency of climatic variation is quite obviously in northwest China. If it goes on like this, its influence will be more severe to the river which meltwater proportion is more than 50%.

LAST GLACIATION AND MAXIMUM GLACIATION IN THE QINGHAI-XIZANG (TIBET) PLATEAU: A CONTROVERSY TO M. KUHLE,S ICE SHEET HYPOTHESIS

Since the late 1950’s, many Chinese scientists have explored the remains of the Quaternary glaciation in the Qinghai-Xizang (Tibet) Plateau and its surrounding mountains. In the main, 3-4 glaciations have been recognized. The largest one occurred in the Late Middle Pleistocene with piedmont glaciers, ice caps and trellis valley glaciers in many high peak regions. But here is no evidence of a unified ice sheet covering the whole plateau as described by M. Kuhle. Due to the further uplifting of the Himalayas and Qinghai-Xizang Plateau the climate became progressively drier, diminishing the extension of glaciers during the Late Pleistocene. The elevation of the snow line during the Last Glaciation was about 4,000 m on the south, east and northeast edges of the plateau and ascended to 5500 m on the hinder northwest of the plateau. The thermal effect of the big plateau massif, the sharp increase of aridity from the southeast rim to the northwest inland area and the abrupt decrease of precipitation during

RELATION BETWEEN δ^(18)O IN ATMOSPHERIC PRECIPITATION AND TEMPERATURE AND PRECIPITATION

The paper analyzes the relation between δ(18)O and temperature and precipitation in different regions of the world on the basis of the data from the global observational network set by the International Atomic Energy Agency (I-AEA) and the World Meteorological Organization (WMO). The results show that there is the marked positive correlation between δ(18)O and temperature in the mid-high latitude continent regions, and the marked negative correlation between δ(18)O and precipitation in the mid-low-latitude ocean and coast stations.

Amplitude of climatic changes in Qinghai-Tibetan Plateau

On the basis of ice core and meteorological data from the Qinghai-Tibetan (Q-l) Plateau, this article focuses on the discussion of the problems related to the sensitivity of temporal and spatial changes of the climate in high-altitude regions, particularly in the Q-T Plateau. The features of abrupt climatic changes of the past 100 ka, 2 000 a and recent years indicate that the amplitude of these changes in the Q-T Plateau was obviously larger than that in low-altitude regions. The scope of temperature change above 6 000 m in the Q-T Plateau between glacial and interglacial stages could reach over 10C℃, but only about 4℃ in low-elevation regions close to sea level. During the last 2 000 a, the amplitude of temperature changes at Guliya (over 6 000 m a.s.l.) in the Q-T Plateau reached 7℃, in comparison with 2℃ in eastern China at low altitude. In the present age, apparent differences of climatic warming have been observed in the Q-T Plateau, indicating that the warming in high-elevation regions is

A model for simulating the response of runoff from the mountainous watersheds of inland river basins in the arid area of northwest China to climatic changes

A model for simulating the response of monthly runoff from the mountainous watersheds to climatic changes is developed.The model is based on the modifications to the HBV runoff model, and therefore represents the characteristics and runoff generation processes of inland river basins in the arid area of northwest China. Taking the mountainous watershed of an inland river, the Heihe River originating from the Qilian Mountains and running through the Hexi Corridor as an example, the monthly runoff changes under different climate scenarios are simulated. The simulation indicates that, during the years from 1994 to 2030, if the annual mean air temperature increases by 0.5℃, and precipitation keeps unchanged, then the runoff of May and October will increase because of the increase of the snow melt runoff, but the runoff of July and August will decrease to some extent because of the increase of evaporation, and as a result, the annual runoff will decrease by 4％. If the precipitation still keeps unchanged,

PRELIMINARY RESEARCHES ON LICHENOMETRIC CHRONOLOGY OF HOLOCENE GLACIAL FLUCTUATIONS AND ON OTHER TOPICS IN THE HEADWATER OF URUMQI RIVER, TIAN-SHAN MOUNTAINS

This paper introduced briefly the research results on lichenometry of the Holoceneglacial fluctuations in the headwater of the Urumqi River, in the central TianshanMountains and discussed the histories of the Holocene glaciers and the climate. It isconsidered that lichenometry is one applicable method for dating the mid- and late-Holocene deposits in the cold and mountainous regions. Rhizocarpon geographicum (L.)DCand Xanthoria elegans (Link.) Th. Fr. could be used for dating the deposits of about 4500and 500 a B.P. respectively. There existed at least four periods of glacial advances whichoccurred before about 5700, 4100, 2800 and 403- 74 a B. P. respectively with the firstperiod the longest. Little Ice Age includes three stages of glacial advances which endedbefore about 403, 208 and 74 a B. P. respectively with the second stage the maximum.During the general Holocene warming processes, there existed at least four cold peri-ods which ended before about 5700, 4100, 2800 and 420- 91 a B.P. respectively,

Response of the snowmelt and glacier runoff to the climate warming-up in the last 40 years in Xinjiang Autonomous Region,China

Some analytical results of the measured runoff during 1950s to 1980s at outlet hydrological stations of 33 main rivers and climatic data collected from 84 meteorological stations in Xinjiang Autonomous Region are presented.Comparison of hydrological and climatic parameters before and after 1980 shows that the spring runoff for most rivers after 1980s increased obviously at a rate of about 10％, though the spring air temperature did not rise very much. Especially,an increment by 20％ for alpine runoff is observed during May when intensive snow melting occurred in the alpine region. To the contrary, the runoff in June decreased about 5％. When the summer or annual runoff is taken into account,direct relationship can be found between the change in runoff and the ratio of glacier-coverage, except the runoff in August when the glacier melting is strong, indicating that climatic warming has an obvious effect on the contribution of glacier melting to the runoff increase.

Variational features of precipitation δ^(18)O in Northeast Qinghai-Tibet Plateau

There is a marked positive correlation between δ18O in atmospheric precipitation andtemperature in the Northeast Qinghai-Tihet Plateau.The amount effect in Tuotuohe station is notable as thetemperature is greater than or equal to 7.3℃,so is in Xining as 8.3℃.The analytic results show that thesynoptic and climatic significance of different time scales is different,and their degrees are also different.Moreover,the relations between the weather systems in the Northeast Qinghai-Tibet Plateau and δ18O inprecipitation are analyzed.Under the influence of continental air mass the δ18O change in the Plateau issynchronous with that of temperature and under the oceanic air mass originated from the Bengal Bay and theArabian Sea there is a marked negative correlation between δ18O and precipitation amount or temperature in themonsoon region of the Plateau and also positive one between δ18O and temperature in the non-monsoon region.

RESULTS OF SOLID PRECIPITATION MEASUREMENT INTERCOMPARISON IN THE ALPINE AREA OF RUMQI RIVER BASIN

I. INTRODUCTIONMany studies have shown that precipitation gages offer lower precipitation to some extent, that is, the measured precipitation (P_m) is lower than the true one (P_t), because of the systematic errors caused by the deformation of the wind field over gages’ orifices (wind effect, △P_a), the adhesion of rain drops and snow-melted water

Impact of climate change on surface water resource and tendency in the future in the arid zone of northwestern China

The surface water resource in the arid zone of northwestern China is pregnant in the 6great mountain systems induding snow covers,glaciers,rivers and lakes.Though the climate fluctuates,becoming warmer and drier,and the water resource trends to wither during the 20th century,it is evident thatin the Holocene Megathermal there would be a more plentiful water resource.During the Little Ice Age,theglacier area and the amount of runoff and lake water were also higher than those at present.It is estimated thatthe temperature in mountains of western China would be 1℃ warmer by 2030 A.D.,when the precipitationand evaporation would be some higher,the snow cover would be lower in plains and higher in mountains,gla-ciers would retreat further,many small glacier would disappear,river runoff would increase with a highervariability,most of the lakes would be in a negative balance state and would wither further.

Variation of snow water resources in northwestern China,1951—1997

An observation study is carried out on snow mass amount estimate in northwestern China by using microwave derived snow depth charts employing data from SMMR in conjunction with daily snow depth, density and snow cover duration records for 46 ground climate stations. Spatial patterns, seasonal cycle, and interannual variation of snow cover are discussed. Results show that snow cover is the second largest water supply over the arid northwestern China,and unlike most other areas in the world, northwestern China did not experience any decrease in snow cover since 1987.Secular trends reveal systematic increase in snow mass and durations. Analysis of snow cover-climate relationship indicates that gradual increase in snow cover is primarily in response to increase in snow season precipitation.

Nonlinear analysis for the coupled problem of temperature and seepage fields in cold regions tunnels

The governing differential equations of the coupled problem of temperature and seepage fields with phase change are first derived from the theory of heat transfer and the theory of seepage. The finite element formulae of this problem are obtained from Galerkin’ s method. And considering the seepage influence, an illustrative example of thetemperature field in a cold-region tunnel is provided.The example shows that the influence of seepage on the frozen depth of the tunnel is very great, and thus the effect of the seepage factor should be taken into account in the engineering design.

Study on the glacier variation and its runoff responses in the arid region of Northwest China

The glaciers in the arid region of Northwest China are viewed as an independent system, and glacier variation and mass balance fluctuation since the Little Ice Age and in the recent decades are estimated. Based on the estimation, the threshold time of glacier runoff against the backgrounds of the current and future varying climate conditions is simulated.

THE HISTORICAL CLIMATIC RECORDS IN ICE CORES FROM THE SURFACE LAYER OF WILKES LAND, ANTARCTICA

The information preserved in the surface layer of the Antarctic ice sheet is so abundant and detailed that in the areas with a high accumulation rate the annual climatic changes in the past can be distinguished. After conducting an investigation into the stratigraphical features of ice cores from two typical shallow boreholes in the Wilkes Land, one inland and another near the margin, analyzing δ（18）O and the gross β radioactivity in the cores, as well as anslyzing the power spectra of δ18O, the authors present some important assessments on the climatic information in the past several decades therein such as the annual mean temperature and precipitation, and suggest that there is a period of 11 years with which the climate changes cyclically in East Antactica. Such a studying method will be of value in both theory and practice to the inland Antarctica, where direct meteorological observation is deficient.

EVALUATING THE WATER RESOURCE IMPACTS OF CLIMATIC WARMING IN COLD ALPINE REGIONS BY THE WATER BALANCE MODEL: MODELING THE URUMQI RIVER BASIN

In view of the tendency of global climatic warming, the water balance model is employed to estimate the runoff changes in the Urumqi River Basin, Xinjiang Region, China, under ten climate change scenarios, which are combinations of temperature increases by 2K and 4K with precipitation change of 0, ±10% and ±20%, respectively, as the atmospheric concentration of carbon dioxide increases. The results suggest that runoff changes mainly depend on the precipitation change in the glacier-free or less glacierized basins in cold alpine regions. Effect of temperature on runoff becomes marked gradually with the increase in precipitation. Runoff from glacierized areas, however, is much more sensitive to the temperature change.

Climates and Environments of the Holocene Mega thermal Maximum in China

Based on data from palynology, paleosols, paleolimnology, ice core, archeology, sea levels, etc. , we reconstructed climates and environments of the Holocene Megathermal maximum (7. 2-6. 0 ka B. P. ), particularly vegetation zones, temperatures, precipitation and sea-level fluctuations. Annual mean temperature during that period was estimated at 1 ℃ higher than today for South China, 2 ℃ higher for the Changjiang River Valley, about 3℃ higher for North China, Northeast China and Northwest China and up to 4 - 5 ℃ higher for southern Qinghai-Xizang Plateau. Relative winter temperatures increased much more than average annual temperatures. The centennial-scale warming was accompanied by the expansion of summer monsoon and recession of winter cold currents as well as northward and westward shift of vegetation zones. Higher lake levels registered in all inland lakes of Inner Mongolia, Xinjiang, Qinghai and Xizang indicated that precipitation increased to a certain extent. The Holocene highest sea level

MATHEMATICAL MODELING OF VARIATIONS ON STABLE ISOTOPIC RATIOS IN FALLING RAINDROPS

The variations of stable isotopic contents in falling raindrops are not only influenced by the humidity conditions, but also by the stable isotopic contents in atmospheric vapor to a certain extent. If there is a difference between the isotopic contents in the vapor of the surrounding air and at the surface of the raindrops, the move of the isotopic contents from high to low values will be produced. Usually. influenced by the evaporation process, the stable isotopic ratios in raindrops are constantly increased in the unsaturated atmosphere. The less the atmospheric humidity, the more obvious the increased range. As the enrichment rate of stable isotopes in raindrops is equal to the outward isotopic move rate. the 'pseudo-equilibrium state' appears. The influence of evaporation on stable isotopic contents disappears in the saturated atmosphere, so that the magnitude of isotopic ratio in raindrops is dependent on the isotopic exchange between the raindrops and the surrounding atmosphere.

Distribution of deuterium excess in surface snow of the Antarctic ice sheet

Analysis of stable isotope ratios, δ18O and δD, in snow and ice in cold regions has long been one of the most important tools for reconstructing the paleoclimatic history. Recently, attention has been paid to the deuterium excess （exD）, which has also been recognized as a source of information about the vapor source regions. Distribution of

Distribution of stable isotopes in Antarctic surface snow

Used as a climatic indicator, stable isotopes provide a very powerful tool forreconstructing paleoclimate. The established model with regard to the relationship betweenstable isotopes and temperature based on the data obtained from Dumont d’Urville Stationto Dome C in the Antarctica was widely used in ice core research. The Antarctica is anextremely large continent. Does a modeling based on one point or one profile fit to

CALCULATING FORMULA OF TIME-DEPENDENT TEMPERATURE REGIME OF FROZEN SOIL

Thermodynamic study of permafrost in cold regions began when the unsteady solution of 1-D and initial condition problem involving phase change was first given by Stefan in 1890. In 1973, the problem with boundary value of A·τ1/2+B·τ type was solved analytically by using variant substitute method by G.M. Felydman and it is a milestone in solving the problem with changeable boundary condition. In 1981, using small