Abstract: Yulin locates on a typical agropastoral ecotone of North China between Loess Plain in Shaanxi Province and Mu Us sandy land in Inner Mongolia Autonomous Region. In order to understand the development trend and characteristic of climate change in Yulin region, the paper used spatial interpolation to analyze seasonal and interannual trend and characteristic of climate in Yulin on the basis of meteorological data in Yulin during 1970-2010. Five meteorological indexes (such as, average minimum temperature, average maximum temperature, precipitation, and solar radiation) were used for the analysis of climatic characteristics, for example, change trend, periodic variation, and abrupt change. Five meteorological indexes were interpolated into raster layers by using of Kring method, and further clipped by the administrative line of Yulin region. The average value of five metrological indexes in Yulin region were abstained from raster layers based on spatial overlay analysis at last. Then, regression analysis and moving average method were used for trend analysis, Mann-Kendall method and Moving [WTBX]t[WTBZ]-test technique for abrupt change, and wavelet analysis for periodic analysis. Through the analysis above, the results indicate that the average temperature in Yulin increased during 1970-2010. The temperature in spring and winter contributes relatively higher to the rising of annual temperature than that in summer and autumn. Annual and seasonal precipitation fluctuated obviously during this period. The precipitation in summer reduced relatively higher than that in other season. As well, the precipitation increased before 1990s, decreased at the beginning and middle of 1990s, and picked up since the late 1990s. The solar radiation in past 41 years had a downward trend, and reduction of the solar radiation in summer showed higher contribution to the decreasing of annual solar radiation. The periodic variation of five meteorological indexes was much stable in the lager time scale, such as 25-32 years. Precipitation and average minimum temperature in the four seasons owned obvious periodic characteristic at three kinds of time scale. In addition, except for precipitation in spring, the frequency of meteorological factors in other seasons during 1970-2010 had a rising trend, and the time interval decreased. Thus, the climate change was much active during the last 10 or 20 years in this region.

Key words: solar radiation, interannual variation, trend analysis, wavelet analysis, abrupt climate change