The Variations Of Runoff Over The Source And Course Region Of The Tarim River And Its Meteorological Factors Concerned

In this paper, the runoff, air temperature and precipitation situation over the source and course region of the Tarim River and its meterological factors are comprehensively studied. Different datasets are used in this study, including (1) the monthly mean air temperature, precipitation and runoff information of the 23 stations in the source and course region of the Tarim River from 1961 to 2004;(2) the height serial of the 0℃ layer at 8 AM in Akesu station from 1986 to 2003.(3) the snow cover with remote sensing data from Meteorological Satellite EOS/MODES from 2000 to 2004;(4) the monthly mean 500 hPa geopotential height and surface temperature from NCAR/NCEP reanalysis dataset from 1961 to 1998.The runoff over the source and course region of the Tarim River is obviously increasing. The reason may be contributed to the lag effect of the temperature rise, especially after the 1990s. The variation period of the runoff is about 3.8 to 4.3 years. Based on the annual runoff information, we choosed 6 cases of the extreme "High" and "Low" years( "High" year means the runoff is high, "Low" year means the runoff is low). The result of the statistical analysis show that during the "High" year, it is colder in the winter and warmer in the summer. The situation is different during "Low" years. It is drier and colder in winter and summer.The 500hPa geopotential height are also examined to find out the relationship between the runoff and atmospheric circulation. In winter (January), both are 3-wave patterns. The difference is in the position of the polar vortex. In summer (July), the west PacificSubtropical High is more west and the Iran High is more north and east. The variation of the Subtropical High and Iran High could influenced the increasing of the runoff of the Tarim region.The teleconnection relationship is also examined between the variables of the Tarim region and the SSTA of the Pacific. There is a key area, that is , the south of the California cold current area. In this area, the correlation coeffiences are positive.In order to find out the meteorological factors to influence the runoff, the relationship between the runoff and the precipitation, temperature in Wensu, Akesu and Keping is computed. The correlation between the runoff and the height at 0 C layer in Akesu is also computed. The result show that the increasing of the runoff is highly related to the temperature rise, while the influence of the precipitation is weak.The snow cover of the source and course region of the Tarim River is examined to test the influence of the former period. It is shown that the reason of the runoffs variation is owe to variations of the precipitation and temperature in the former winter. If the snow cover is thick in the winter, which means the abundant reservation of the solid water. With the rise of the temperature in Spring and summer, the stream flow of the river would be definitely more abundant, which is the important supply to the runoff. The abrupt increasing of the temperature and precipitation in summer will result in the increasing of the runoff, which is the main reason to cause the flood.