Abstract: The spatial distribution of precipitation is uneven in Big Xi'an region. According to the monthly precipitation data from 14 meteorological stations in Big Xi'an during 1970-2013, we analyzed the spatial and temporal variations of precipitation in five areas of Big Xi'an region by using moving average method, Mann-Kendall test method, wavelet analysis method and the Kriging interpolation method. Results show that the average annual precipitation in Big Xi'an region was 576.65 mm, decreasing overall with a rate of -10.04 mm/10 a. Decreases in precipitation in the east and north of Xi'an were more obvious than those in the west and south. Moreover, the distribution of precipitation in a year was uneven, mainly from July to September, accounting for 50.84% of the total annual precipitation. In addition, precipitations in spring and autumn presented a downward trend, but precipitation in summer was in an upward trend. The first main period of annual precipitation change in the study area was 28 years. Precipitation in multiple years in the area experienced a fluctuation in “less-more-less-more” trend, with abrupt changes in 1980 and 1991; but interdecadal precipitation in the study area showed a trend from increase to decline and then to increase. In addition, the spatial distribution of annual precipitation is uneven, gradually decreasing from the southeast to the northwest. The research results could offer reference to the rational utilization of precipitation resources in Big Xi'an region.

Key words: Big Xi'an region, precipitation variation, spatial distribution, Mann-Kendall test, Kriging interpolation method