Climatic change features of rainfall in Lhasa from 1952 to 2005

Lhasa is positioned at the South of the Qinghai-Xizang Plateau with a temperate and semi-arid plateau climate, annual average rainfall of 426.5mm. Summer drought takes place frequently here with a distinct precipitation variation, which obviously influences the agricultural production. On the basis of climate diagnosis and analysis methods, this paper presents the detailed study on the characteristics of the interannual -interdecadal variation of precipitation and rainfall day in the recent 50 years. Using the data of monthly rainfall and annual rainy days from 1952 to 2005 in ere analyzed. The results show that the annual rainfall displayed insignific Lhasa of Tibet, the interannual and interdecadal variations of the annual and seasonal rainfall,annual rainy days want decreasing trend in Lhasa in former 30 years(1952-1980) with a decrease of 17.8mm/10 a, but the significant increase for annual rainfall indicated an increase of 90.6 mm/10 a in the last 25 years(1981-2005). In past 50 years, the trend of seasonal rainfall was increase in all season (except summer), especially in autumn. In addition, the annual rainy days of ≥0.1 mm≥1.0 mm and ≥5.0mm were increase in past 50 years. The trend of increase for annual rainy days of ≥10.0mm was significant with an increase of 3.6d/10a in the last 25 years. However, from the 1950s to 1980s, the interdecadal variations of rainfall was decreased in summer, increased in autumn, whereas negative anomaly in winter. The annual rainy days were less in 1980s, more in the 1990s. The years with exiguous annual rainfall and anomalous drought appeared in 1980s, one anomalous moistness year in both early 1950s and early 1960s, and there were no anomalous years in the 1970s. The annual rainfall in Lhasa during recent 50 years had mainly the oscillation periods of quasi 14 years.