Abstract:

Based on daily temperature, precipitation and evaporation data at five meteorological observation stations in Shiyang river basin, temporal and spatial characteristics of interdecadal variability of three elements were analyzed by methods of a liner tendency rate, a Mann-Kendall test and a Kriging interpolation. The results indicate that the minimum increasing rate of air temperature is 0.25 ℃ per decade from 1960 to 2009 in Shiyang river basin, and it is higher than that in the whole China and the globe. Increasing rate of air temperature is higher in the eastern area than in the western area in the study area. Air temperature is in a decreasing trend in 1960s in Shiyang river basin, while it is in an increasing trend during 1970s to 2000s in most areas of this basin. Besides, temperature increase has a mutation phenomenon in Shiyang river basin. Interdecadal precipitation and its average are higher in the western area than in the eastern area. However, increasing rate of precipitation in Shiyang river basin rarely reaches significant level, and precipitation change is caused by its interannual oscillation. Evaporation in most areas of Shiyang river basin increases first and then decreases in the past fifty years. Evaporation has an abrupt change phenomenon in Shiyang river basin, except at Minqin. Drought could become severe in this region because of continuous increase temperature and evaporation as well as both cooperation relations.

Key words: Air temperature, Precipitation, Evaporation, Mutation analysis, Mann-Kendall test