Abstract: The characteristics and changes of arid climate, including temperature, precipitation and other factors, such as drought frequency and soil moisture, were analyzed for 1960-2005 in Tianshui, Gansu Province. The results indicate that precipitation in the 1990s was the least in recent 50 years, the change rate of precipitation has increased obviously since the 21st century. Temperature has increased generally since the 1960s, especially in the 1990s. The soil moisture was the lowest and in serious deficit; and spring drought, early summer drought and midsummer drought occurred more frequently in the 1990s. According to the change characteristics of arid climate and their effects on the growth of grain crops, the influence coefficient of drought to the yield of grain crops was introduced, and levels of the planting risk of main summer and autumn crops were also assessed. Finally, a plan of planting structure adjustment for main grain crops adapting to changes in arid climate is also provided based on a linear risk decision model.

Key words: arid climate change, grain crops, adjustment of planting structure