Variations and trends of the freezing and thawing index along the Qinghai-Xizang Railway for 1966-2004

Annual freezing and thawing index of 7 meteorological stations along the Qinghai-Xizang Railway were calculated based on daily maximum and minimum temperature records for 1966-2004. Trends of annual freezing and thawing index were analyzed using the Mann-Kendall test and a simple linear regression method. The results show that: 1) The mean annual freezing indices range from 95 to 2300 degrees C.d and the mean annual thawing indices range from 630 to 3250 degrees C.d. The mean annual freezing index of the 7 stations exhibited decreasing trends with decreasing rate of -16.6- -59.1 degrees C center dot d/10a. The mean annual thawing index of these 7 stations showed increasing trends with the related decreasing rate is 19.83-45.6 degrees C center dot d/10a. 2) The MK trend test indicated the significant decreasing trends (significant at < 0.05 significant level) in the annual freezing index for most stations except for Golmud. The significant increasing trends can be observed in the annual thawing index for 4 stations except Golmud and Tuotuohe. Golmud was the only station with no trends in both annual freezing and annual thawing index

Some results of snow chemical surveys in the Kunnes River valley, East Tienshan mountains, China

Chemical surveys of snow were carried out in the upper reaches of the Kunnes River, a tributary of the Yili River in East Tienshan Mountains, China. Some surprisingly high values of sodium and potassium (K+ + Na+) ranging from 4.44 to 8.99 mg/l compared with other data from neighboring areas are detected. Moreover, some relative high values of SO42- with mean concentration 15.8mg/l for new snow and 14.40mg/l for deposited snow, ranging from 10.43 to 23.71 mg/l are also found. Therefore, it is inferred that the sodium and potassium (K+ + Na+) are in the forms of sulfate and that the sources of the sulfate are deserts and some dried lakes in Central Asia. It is also found that there is obviously spatial variation of ions such as K+ + Na+, Ca2+, SO42- and HCO3-. The concentrations of K+ + Na+ and SO42- and that of Ca2+ and HCO3- have similar spatial pattern. The temporal pattern of ion concentration of new snow is considered to be mainly controlled by the depth and area of snow cover in the study area and in the areas to the west. (C) 2002 Elsevier Science Ltd. All rights reserved

Magnification of flood disasters and its relation to regional precipitation and local human activities since the 1980s in Xinjiang, Northwestern China

Analyses of flood disasters were conducted using 1950-2001 data on the flood-damaged areas of cropland, the annual number of flood disasters and the direct economic losses in Xinjiang. There is an increasing trend in flood disasters in Xinjiang during the second half of the 20th century, especially since the mid-1980s. Results of a non-parametric Mann-Kendall test on the cropland-flooded index time series revealed an abrupt change in the mid-1980s. The reasons are discussed with respect to changes in annual precipitation and regional human activities, by correlating cropland-flooded area to annual precipitation and three socio-economic parameters (population, cropland area and GDP). The correlation coefficients between the flood-damaged area and the annual precipitation during the periods 1961-1998 and 1987-1998 were substantially higher than during the period of 1961-1986. The correlation coefficients between the flood-damaged area and the three human activity parameters, however, were relatively high for the whole period of 1961-1998, but generally not significant for the 1961-1986 and 1987-1998 periods, separately. These suggest that the occurrence of flood disasters could be mainly induced by local human activities before the mid-1980s, and thereafter mainly by abnormal precipitation in Xinjiang. Meteorological and hydrological records showed that the number of heavy rainfall events and the frequency of rainstorm flood disasters increased since the 1980s. In addition, siltation of reservoirs and loss of flood control structures are partly responsible for the increase of flood-damaged area. These results suggest that the increasing trend in flood disasters in Xinjiang since the middle 1980s could be attributed, at least in part, to an increasing trend in annual precipitation

Rise and decline of ancient salt industry revealed by Na and Ca concentrations in sediments at Zhongba site, Chongqing

Based on dynastic period division and AMS(14)C dating performed on the sedimentary layers at Zhongba and Yuxi sites, and also the analysis of Na, Ca and Mg of 201 sedimentary samples from Zhongba site and that of Ca and Na in 47 sedimentary samples from Yuxi by using an inductively coupled plasma-mass spectrometry (ICP), we found that there were 35 time periods when the contents of Ca and Na were reversely correlated, i.e. whenever the content of Ca was the highest, the content of Na was the lowest, and vice versa. Among them, there were 21 time periods when the content of Ca was the highest, and Na was the lowest, indicating that there were about 21 prosperous periods of ancient salt production at Zhongba site since 3000BC. Other 14 time periods with the peak values of Na while the low values of Ca indicate 14 declined periods of salt production at Zhongba site since 3000BC. The conclusion obtained from the reverse relationship between Ca and Na contents in this paper is consistent with that "the salt production at Zhongba site started in the new stone age, developed in the Xia and Shang dynasties, reached at the heyday in periods from the Western Zhou to the Han Dynasties, maintained stable to develop in the Tang and the Song dynasties, and gradually declined after the Song Dynasty because the sea salt were conveyed into Sichuan region, however, still had production in the 1970s-1980s", educed from archeological exploration. All the above mentioned results indicate that there is a reverse relationship obviously between the contents of Na and Ca in sediments, at Zhongba site for ancient salt production, which can be used to reveal the process of rise and decline of ancient salt industry at Zhongba site