Abstract:

Based on three group resistance line (TGRL)，and with the aim to decrease the error of the calculation of climate change，which can be significantly influenced by outliers，the variation trends of surface air temperature，extreme temperature and cloudiness in Tibet area from 1971 to 2000 were investigated，and the correlation between temperature and cloudiness change of the area was also analyzed. Compared with the results obtained by traditional least square regression method，the calculations of this study showed that the variation trends revealed by TGRL are less than by the latter，indicating that the traditional least square regression method might overestimate the degree of climate change in Tibet. Increasing trend of minimum temperature is the main factor causing the warming tendency in Tibet，and the warming in spring and summer is much more obvious than that in winter. There is a warming tendency with high (low) values in the west and inner (east) region，where the pattern of tendency distribution shows that localization is affected by the complex terrain. Both of the total and low level cloudiness in the area were decreasing in the past 30 years. It was also shown that variations of temperature have a strong correlation with cloudiness，and decrease in cloudiness is an important reason for the warming in Tibet.

Key words: exploratory analysis, three group resistance line(TGRL), trends of climate change, Tibet, Tibetan Plateau