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The present paper aimed to study the effect of meteorological characteristics on the safety of power grid in plateau area. 【Method】In this paper, the reanalysis data(0.125°×0.125°) provided by ECMWF were analyzed in the plateau area, including precipitation, temperature and snow depth. 【Result】The precipitation in summer was obviously higher than the other seasons. There were more precipitation in Shannan area, with an average annual occurrence of 14 extreme precipitation.The temperature of Qinghai-Tibet plateau dropped sharply in winter. The lowest temperature in Lhasa was-14 °C, and the temperature in Changdu was below-6 °C, such cold weather might cause freezing disasters, and there might be ice cover accidents on transmission lines. The variation trend of snow depth on the Tibetan plateau was single peak and it was obviously higher than other seasons in spring and winter. Shannan was a large snowfall area in spring, and its snow depth decreased obviously in summer and autumn. The snowy area in winter enlarged, both Shannan and Linzhi were in the high snowfall area, and the frequency of extreme snowfall events was high. 【Conclusion】We should focus on the characteristics of snow depth in spring and winter in central and Eastern Tibet to prevent the threat to the power grid caused by snow. [ABSTRACT FROM AUTHOR]

The lateral earth pressure coefficient at rest, K0, is an important parameter in geotechnical engineering. There have been many studies for unfrozen soils; however, this is not the case for frozen soils, which impedes reasonable calculation concerning cold regions engineering. This paper introduces a novel triaxial apparatus for frozen soils with reference to that for unfiozen soils. The device is capable of performing experiments on frozen soil samples with K0 status under precisely controlled negative temperature. Two soils along the Qinghai-Tibetan highway are taken as study objects. K0 experiments are carried out with the apparatus and K0 is obtained under different testing conditions. It is found that temperature is a dominant factor in influencing K0 of frozen soils, while stress state and soil type should also be taken into account. [ABSTRACT FROM AUTHOR]

The main portion of Tibetan Plateau has experienced statistically significant warming over the past 50 years, especially in cold seasons. This paper aims to identify and characterize the dynamics of inland lakes that located in the hinterland of Tibetan Plateau responding to climate change. We compared satellite imageries in late 1970s and early 1990s with recent to inventory and track changes in lakes after three decades of rising temperatures in the region. It showed warm and dry trend in climate with significant accelerated increasing annual mean temperature over the last 30 years, however, decreasing periodically annual precipitation and no obvious trend in potential evapotranspiration during the same period. Our analysis indicated widespread declines in inland lake's abundance and area in the whole origin of the Yellow River and southeastern origin of the Yangtze River. In contrast, the western and northern origin of the Yangtze River revealed completely reverse change. The regional lake surface area decreased by 11,499 ha or 1.72% from the late 1970s to the early 1990s, and increased by 6,866 ha or 1.04% from the early 1990s to 2004. Shrinking inland lakes may become a common feature in the discontinuous permafrost regions as a consequence of warming climate and thawing permafrost. Furthermore, obvious expanding were found in continuous permafrost regions due to climate warming and glacier retreating. The results may provide information for the scientific recognition of the responding events to the climate change recorded by the inland lakes. [ABSTRACT FROM AUTHOR]

Abstract: Long-term high-resolution climate proxies are essential for understanding climate variability on the Tibetan Plateau (TP), where few long-term climate records are available. In this paper, we describe a summer (August) temperature reconstruction over the period 1385–2002 based on a tree-ring width chronology of Balfour spruce (Picea likiangensis var. balfouriana) on the southeastern TP created using the Regional Curve Standardization method. The reconstruction explains 44.7% of the variance in the instrumental temperature records during the calibration period (1962–2002), and captures temperature variability over a broad region of the TP. Warmer than average Augusts were found during the periods 1446–1494, 1509–1522, 1553–1567, 1797–1812, 1845–1905 and 1918–2002. Cooler than average Augusts occurred from 1385–1416, 1426–1445, 1495–1508, 1523–1552, 1568–1686, 1695–1718, 1725–1796, 1813–1844 and 1906–1917. A warming trend in the 20th century was unprecedented during the past six centuries. The reconstruction closely matched other tree-ring summer temperature reconstructions from neighboring regions, as well as patterns from ice-core δ18O data, and fluctuated in synchrony with Northern Hemisphere temperature reconstructions. [Copyright &y& Elsevier]

According to simulation analysis of the advanced integral equation model (AIEM), there is a good linear relationship between emissivity and soil moisture under conditions of given roughness. The normalized difference of emissivities at 19.35 GHz and 10.65 GHz with vertical polarization can partly eliminate the influence of roughness and the squared correlation coefficient is about 0.985. This paper uses the normalized brightness temperature for retrieving soil moisture in Tibet from TRMM/TMI data. This method avoids parametrizing the land surface temperature which is a key parameter for the computation of emissivity. We make some sensitivity analysis for the atmosphere which is the main influence factor for our method. The analysis results indicate that our method is very good for clear days but is not very good when there is rainfall. We evaluate our algorithm by using the ground truth data obtained from GAME-Tibet and the retrieval error of soil moisture is about 0.04m3 m-3 relative to experimental data. The analysis indicates that the relationship obtained from the theoretical model should be revised through the local ground measurement data because the method is still influenced by roughness and vegetation. After making a regression revision, the retrieval error of soil moisture is under 0.02m3 m-3. Finally, we retrieve the soil moisture in Tibet from TRMM/TMI data, and the distribution trend of retrieval results is consistent with the real world. [ABSTRACT FROM AUTHOR]

Several multidecadal simulations have been carried out with the new version of the Community Climate System Model (CCSM). This paper reports an analysis of the land component of these simulations. Global annual averages over land appear to be within the uncertainty of observational datasets, but the seasonal cycle over land of temperature and precipitation appears to be too weak. These departures from observations appear to be primarily a consequence of deficiencies in the simulation of the atmospheric model rather than of the land processes. High latitudes of northern winter are biased sufficiently warm to have a significant impact on the simulated value of global land temperature. The precipitation is approximately doubled from what it should be at some locations, and the snowpack and spring runoff are also excessive. The winter precipitation over Tibet is larger than observed. About two-thirds of this precipitation is sublimated during the winter, but what remains still produces a snowpack that is very large compared to that observed with correspondingly excessive spring runoff. A large cold anomaly over the Sahara Desert and Sahel also appears to be a consequence of a large anomaly in downward longwave radiation; low column water vapor appears to be most responsible. The modeled precipitation over the Amazon basin is low compared to that observed, the soil becomes too dry, and the temperature is too warm during the dry season. [ABSTRACT FROM AUTHOR]

This paper presents a large data set on carbon isotope composition (δ13C) of modern soils which were collected under the main vegetation communities along an altitude of 1250–5500 m above sea level in the Qinghai-Tibetan Plateau. The δ13C values of 198 samples range from -28.6 to -15.1‰ versus PDB and exhibit a clean relation to different vegetation communities from forest (-25.9 ± 1.2‰) to shrub (-24.7 ± 1.4‰), steppe (-23.1 ± 1.3‰), alpine meadow (-23.6 ± 0.7‰), alpine desert steppe (-21.3 ± 1.6‰), and alpine desert (-18.9 ± 2.5‰). We attributed the observed variability in δ13C values to that the mean annual precipitation (MAP) and the mean annual temperature (MAT) are the main factors controlling the distribution of vegetation types in the Tibetan Plateau, which causes the change in carbon isotope composition of modern soils at any given altitude. The result of both linear and nonlinear regression analyses also confirms that MAP and MAT are the major factors affecting the δ13C values of surface soils. In the absence of favorable moisture and temperature conditions, low pCO2 alone is not sufficient to cause the distinct changes in carbon isotope composition of modern soils in the Tibetan Plateau. This study provides some fundamental information on the carbon isotope composition of terrestrial carbon pools and bears some practical significance for the use of carbon isotope data to document vegetation changes and environmental conditions of the high plateau in the past. [ABSTRACT FROM AUTHOR]